<b>Bijsluiter</b>. De hyperlink naar het originele document werkt niet meer. Daarom laat Woogle de tekst zien die in dat document stond. Deze tekst kan vreemde foutieve woorden of zinnen bevatten en de opmaak kan verdwenen of veranderd zijn. Dit komt door het zwartlakken van vertrouwelijke informatie of doordat de tekst niet digitaal beschikbaar was en dus ingescand en vervolgens via OCR weer ingelezen is. Voor het originele document, neem contact op met de Woo-contactpersoon van het bestuursorgaan.<br><br>====================================================================== Pagina 1 ======================================================================

<pre>Phenytoin
Evaluation of the effects on reproduction, recommendation for classification
To: the State Secretary of Social Affairs en Employment
No. 2018/15, The Hague, June 27, 2018
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<pre>Contents                                                                                                    Phenytoin | page 2 of 81
contents
     Samenvatting3                                        References54
     Executive summary                                  5 Annexes68
                                                           A   Animal fertility and developmental toxicity studies               69
01 Scope                                                6 B   Abbreviations                                                     79
     1.1  Background                                    7
     1.2  Committee and procedure                       7 The Committee                                                        80
     1.3  Labelling for lactation                       8
     1.4  Data                                          8
     1.5  Presentation of conclusions                   9
     1.6  Final remark                                  9
02 Phenytoin                                          10
     2.1  Properties                                   11
     2.2  Context                                      11
     2.3  Human studies                                12
     2.4  Animal studies                               33
     2.5  Conclusions                                  48
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<pre>Samenvatting                                                                                                                  Phenytoin | page 3 of 81
samenvatting                                                                                        en kwaliteit van moedermelk) beoordeeld en de
                                                                                                    effecten via de moedermelk op de zuigeling.
                                                                                                    De commissie beoordeelt of er aanwijzingen zijn
Op verzoek van de minister van Sociale Zaken        Gebruik van fenytoïne                           dat de stof een schadelijk effect kan hebben. Als
en Werkgelegenheid (SZW) heeft de                   Fenytoïne is een synthetisch geneesmiddel. Het  dergelijke aanwijzingen bestaan stelt ze voor om
Gezondheidsraad het effect beoordeeld dat het       wordt voornamelijk gebruikt tegen epileptische  de stof in te delen in een bepaalde
geneesmiddel fenytoïne heeft op de                  aanvallen, maar soms ook bij                    gevarencategorie, die aangeeft hoe sterk de
voortplanting.                                      hartritmestoornissen. Mensen die werkzaam zijn  bewijskracht is voor het schadelijke effect van
Dit advies is opgesteld door de commissie           in de farmaceutische industrie, in apotheken of de stof. Op basis van dat voorstel kan de
Classificatie reproductietoxische stoffen – hierna  in ziekenhuizen kunnen tijdens hun werk in      minister van SZW besluiten om de stof al dan
aangeduid als de commissie – een                    aanraking komen met fenytoïne.                  niet als reproductietoxische stof aan te merken.
subcommissie van de vaste commissie                                                                 De indeling in gevarencategorieën is gebaseerd
Gezondheid en beroepsmatige blootstelling aan       Classificeren naar bewijskracht voor            op EU-verordening (EG) 1272/2008.
stoffen (GBBS).                                     schadelijk effect
De Gezondheidsraad heeft een vaste rol bij de       Bij de beoordeling van effecten op de           Advies aan de staatssecretaris
bescherming van werknemers tegen mogelijke          voortplanting kijkt de commissie zowel naar de  Op grond van de beschikbare wetenschappelijke
schadelijke effecten van stoffen waar zij tijdens   effecten op de fertiliteit (vruchtbaarheid) van gegevens stelt de commissie voor om fenytoïne
hun werk mee in aanraking kunnen komen.             mannen en vrouwen als naar de effecten op de    alleen voor effecten op de ontwikkeling in te
Meer informatie over die rol staat op www.          ontwikkeling van het nageslacht. Daarnaast      delen in een gevarencategorie. Over de effecten
gezondheidsraad.nl.                                 worden de effecten op de lactatie (hoeveelheid
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<pre>Samenvatting                                                                                        Phenytoin | page 4 of 81
op de vruchtbaarheid en op of via lactatie zijn        1B (stoffen waarvan verondersteld wordt dat
onvoldoende geschikte gegevens beschikbaar.            zij toxisch zijn voor de menselijke
                                                       voortplanting) en te etiketteren met H360D
Classificatievoorstel commissie voor fenytoïne         (kan het ongeboren kind schaden).
• voor effecten op de fertiliteit adviseert de      • voor effecten op of via lactatie adviseert de
  commissie fenytoïne niet in te delen in een          commissie om fenytoïne niet te etiketteren
  gevarencategorie wegens onvoldoende                  wegens onvoldoende geschikte gegevens.
  geschikte gegevens.
• voor effecten op de ontwikkeling adviseert de
  commissie fenytoïne in te delen in categorie
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<pre>Executive summary                                                                                                                  Phenytoin | page 5 of 81
executive summary                                                                                       Recommendations to the State Secretary
                                                                                                        Based on the available scientific data, the
                                                                                                        Committee recommends to classify phenytoin
At the request of the Minister of Social Affairs     occupationally exposed to phenytoin in the         only for effects on offspring development.
and Employment, the Health Council of the            pharmaceutical industry, in pharmacies or in       There are insufficient data for classification
Netherlands evaluated the effects of phenytoin       hospitals.                                         with regard to effects on paternal and
on reproduction. This advisory report has been                                                          maternal fertility and effects on or via
drafted by the Subcommittee on the                   Classification according to strength of            lactation.
Classification of Reproduction Toxic Substances      evidence for toxic effect
of the Dutch Expert Committee on Occupational        For assessing the effects on reproduction, the     The Committee’s classification proposal for
Safety (DECOS) of the Health Council, hereafter      Committee evaluates the effects on male and        phenytoin:
called the Committee. The Health Council has a       female fertility and on the development of the     • For fertility, the Committee recommends not
permanent task in assessing the hazard of            offspring. Moreover, the Committee considers          classifying phenytoin due to a lack of
substances to which man can be occupationally        the effects of a substance on lactation and on        appropriate data.
exposed. More information about this task can        the offspring via lactation.                       • For developmental toxicity, the Committee
be found at www.gezondheidsraad.nl.                  If there are data indicating hazardous properties,    recommends to classify phenytoin in category
                                                     the Committee recommends classification in a          1B (presumed human reproductive toxicant)
Use of phenytoin                                     category based on the strength of the evidence.       and to label it H360D (may damage the
Phenytoin is a synthetic anticonvulsant, which       Based on that proposal, the Minister of Social        unborn child).
can be used in the treatment of most types of        Affairs and Employment can decide whether to       • For effects on or via lactation, the Committee
seizure disorders and status epilepticus.            classify the substance as toxic to reproduction.      recommends not labelling phenytoin due to a
Occasionally, phenytoin is used as an                The classification is performed according to          lack of appropriate data.
antiarrhythmic drug. Workers can be                  EU-regulation (EC) 1272/2008.
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<pre>chapter 01 | Scope                                    Phenytoin | page 6 of 81
01
scope
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<pre>chapter 01 | Scope                                                                                                                                        Phenytoin | page 7 of 81
                                                                              Classification concerning fertility (F/f) and offspring development (D/d)a:
1.1 Background                                                                Category 1        Known or presumed human reproductive toxicant (H360(F/D)).
As a result of the Dutch regulation on registration of compounds toxic to     Category 1A       Known human reproductive toxicant .
                                                                              Category 1B       Presumed human reproductive toxicant.
reproduction that came into force on 1 April 1995, the Minister of Social     Category 2        Suspected human reproductive toxicant (H361(f/d)).
Affairs and Employment requested the Health Council of the Netherlands        No classification for effects on fertility or development.
                                                                              Classification for lactation
to classify compounds toxic to reproduction. This classification is                             Effects on or via lactation (H362).
performed by the Health Council’s Subcommittee on the Classification of                         No labelling for lactation.
                                                                              Hazard statement codes:
Reproduction Toxic Substances of the Dutch Expert Committee on                H360F             May damage fertility.
                                                                              H360D             May damage the unborn child.
Occupational Safety (DECOS). The classification is performed according
                                                                              H361f             Suspected of damaging fertility.
to European Union Regulation (EC) 1272/2008 on classification, labelling      H361d             Suspected of damaging the unborn child.
                                                                              H360FD            May damage fertility. May damage the unborn child.
and packaging (CLP) of substances and mixtures. The CLP regulation is         H361fd            Suspected of damaging fertility. Suspected of damaging the unborn child.
                                                                              H360Fd            May damage fertility. Suspected of damaging the unborn child.
based on the Globally Harmonised System of Classification and Labelling       H360Df            May damage the unborn child. Suspected of damaging fertility.
of Chemicals (GHS). The Subcommittee’s advice on the classification will      H362              May cause harm to breast-fed children.
                                                                            a
                                                                               Substances in category 1 are assigned F or D, substances in category 2 f or d.
be applied by the Ministry of Social Affairs and Employment to extend the
existing list of compounds classified as reproductive toxicant (category 1A
and 1B and 2) or compound with effects on or via lactation.                 The classification and labelling of substances is performed according to
                                                                            the guidelines of the European Union (Regulation (EC)1272/2008). The
1.2 Committee and procedure                                                 classification of compounds is the result of an integrated assessment of
This document contains the recommendations for classification of            the nature of all parental and developmental effects observed, their
phenytoin by the Health Council’s Subcommittee on the Classification of     specificity and adversity, and the dosages at which the various effects
Reproduction Toxic Substances, hereafter called the Committee. The          occur. The guideline necessarily leaves room for interpretation, dependent
members of the Committee are listed on the last page of this report.        on the specific data set under consideration. In the process of using the
The classification is based on the evaluation of published human and        regulation, the Committee has agreed upon a number of additional
animal studies concerning adverse effects with respect to fertility and     considerations.
offspring development as well as adverse effects on or via lactation.
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<pre>chapter 01 | Scope                                                                                                                                            Phenytoin | page 8 of 81
 Additional considerations to Regulation (EC) 1272/2008                                                 1.3 Labelling for lactation
 If there is sufficient evidence to establish a causal relationship between human exposure to the
 substance and impaired fertility or subsequent developmental toxic effects in the offspring, the       The recommendation for classifying substances for effects on or via
 compound will be classified in category 1A, irrespective of the general toxic effects (see Regulation
 (EC) 1272/2008, 3.7.2.2.1.).
                                                                                                        lactation is also based on Regulation (EC) 1272/2008. The criteria
 Adverse effects in a reproductive study, reported without information on the parental or maternal      define that substances which are absorbed by women and have been
 toxicity, may lead to a classification other than category 1B, when the effects occur at dose levels
 which cause severe toxicity in general toxicity studies.                                               shown to interfere with lactation or which may be present (including
 Clear adverse reproductive effects will not be disregarded on the basis of reversibility per se.
 The Committee does not only use guideline studies (studies performed according to OECDa standard       metabolites) in breast milk in amounts sufficient to cause concern for
 protocols) for the classification of compounds, but non-guideline studies are taken into consideration
                                                                                                        the health of a breastfed child, shall be classified and labelled. Unlike
 as well.
                                                                                                        the classification of substances for fertility and developmental effects,
 a
     Organisation for Economic Cooperation and Development
                                                                                                        which is based on hazard identification only (largely independent of
Regarding fertility, the Committee takes into account data on                                           dosage), the labeling for effects on or via lactation is based on risk
parameters related to fertility, such as seminal fluid volume and                                       characterization and therefore, it also includes consideration of the level
spermatozoa concentration, that are related to male fertility. The                                      of exposure of the breastfed child.
Committee excludes publications containing only data on sex hormone                                     Consequently, a substance should be labelled for effects on or via
levels from the assessment, because the relationship between these                                      lactation when it is likely that the substance would be present in breast
hormone levels and functional fertility (ability to conceive children) is too                           milk at potentially toxic levels. The Committee considers a concentration
uncertain.                                                                                              of a compound as potentially toxic to the breastfed child when this
In 2017, the President of the Health Council released a draft of the                                    concentration leads to exceeding the exposure limit for children, or, if
report for public review. The Committee has taken the comments                                          that level is unknown, the exposure limit for the general population, e.g.
received into account in deciding on the final version of the report.                                   the acceptable daily intake (ADI).
These comments, and the reply by the Committee, can be found on the
website of the Health Council.                                                                          1.4 Data
                                                                                                        Literature searches were conducted in the on-line databases Current
                                                                                                        Contents and Medline, from 1966 up to May 2011 and by searches on
                                                                                                        internet; updates were performed in TOXNET, the last search was
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<pre>chapter 01 | Scope                                                                                                                 Phenytoin | page 9 of 81
performed in July 2017. Literature was selected primarily on the basis of     1.6 Final remark
the text of the abstracts. Publications cited in the selected articles, but   The classification of compounds is based on hazard evaluation (Niesink
not selected during the primary search, were reviewed if considered           et al., 1995)1 only, which is one of a series of elements guiding the risk
appropriate. In addition, handbooks and a collection of most recent           evaluation process. The Committee emphasizes that for derivation of
reviews were consulted as well as several websites regarding                  health based occupational exposure limits these classifications should
(publications on) toxicology and health. References are divided in            be placed in a wider context. For a comprehensive risk evaluation,
literature cited and literature consulted, but not cited.                     hazard evaluation should be combined with dose-response
The Committee describes both human and animal studies in the text.            assessment, human risk characterization, human exposure assessment
The animal data are described in more detail in Annex A as well. Of           and recommendations of other organizations.
each study, the quality of the study design (performed according to
internationally acknowledged guidelines) and the quality of
documentation is considered.
In the assessment of the potential adverse effects of phenytoin on
reproduction, the Committee also used data on adverse effects related
to its application as a therapeutic agent.
1.5 Presentation of conclusions
The classification is given with key effects, species and references
specified. In case a substance is not classified as toxic to reproduction,
one of two reasons is given:
• Lack of appropriate data precludes assessment of the compound for
    reproductive toxicity.
• Sufficient data show that no classification for toxicity to reproduction is
    indicated.
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<pre>chapter 02 | Phenytoin                                Phenytoin | page 10 of 81
02
phenytoin
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<pre>chapter 02 | Phenytoin                                                                                                                                                        Phenytoin | page 11 of 81
                                                                                                     Mechanism      :     The motor cortex appears to be the primary site of action where spread of seizure
                                                                                                                          activity is inhibited. Phenytoin tends to stabilize the threshold against
2.1 Properties                                                                                                            hyperexcitability possibly by promoting sodium efflux from neurons. This includes
                                                                                                                          the reduction of posttetanic potentiation at synapses. Loss of posttetanic
 Name          :  Phenytoin                                                                                               potentiation prevents cortical seizure foci from detonating adjacent cortical areas.
 CAS-no        :  57-41-0                                                                                                 Phenytoin can reduce the maximal activity of brain stem centres responsible for
 Synonyms      :  Diphenylhydantoin; Fenitoina; Phenantoinum; Phenytoinum;                                                the tonic phase of tonic-clonic (grand mal) seizures.
                  5,5-Diphenylhydantoin; 5,5-Diphenylimidazoline-2,4-dione                           Kinetics       :     Oral bioavailability of phenytoin is high (90%). Phenytoin is widely distributed
 Trade names   :  Dantoin, Dilantin, Diphenlyn, Phenyltoin, Divulsan, Novo-diphenyl, Phentoin                             throughout the body and more than 90% of the circulating drug is protein-bound,
                  sodium, Denyl sodium, Dilantin sodium, Diphentoin, Diphenylan sodium,                                   mainly to albumin. The half-life is dose-dependent and has an average of 20 to 30
                  Kessodanten, Elsanutin, Phentoin, Di-Hydan, Phenhydan                                                   hours for a therapeutic dose. Phenytoin is metabolized in the liver by cytochrome
 Structural    :  Phenytoin                                                                                               P450-2C9 and -2C19. Most of the drug is excreted in the bile as inactive
 formula                                                                                                                  metabolites which are then reabsorbed from the intestinal tract and excreted in
                                                                                                                          the urine. Urinary excretion of phenytoin and its metabolites occurs partly with
                                                                                                                          glomerular filtration but more importantly by tubular secretion. Phenytoin
                                                                                                                          accumulates in fat tissue.
                                                                                                     Data from HSDB3, unless otherwise noted
                                                                                                    2.2 Context
 Use           :  Phenytoin is a commonly prescribed synthetic anti-epileptic, which can be used in Epilepsy is the most common neurological disorder in women of
                  the treatment of most types of seizure disorders and status epilepticus.
                  Occasionally, phenytoin is used as an antiarrhythmic drug. It is incidentally     reproductive age. Women with epilepsy are at risk of reproductive
                  prescribed off-label for treatment of skin disorders. Phenytoin may be
                                                                                                    dysfunction, through ovulatory failure for instance (Morrell et al., 2002;
                  administered orally or intravenously at doses of 300 – 600 mg/day. The
                  therapeutic plasma level is 10-20 μg/ml.                                          Bauer et al., 2008).4,5 Approximately eight in 1,000 pregnancies occur
 Occupational  :  Can occur in the pharmaceutical industry, in pharmacies or in hospitals.
 exposure                                                                                           among women with epilepsy part of whom are taking antiepileptic drugs
 Mol weight    :  252.268 g/mol
                                                                                                    (Fairgrieve et al., 2000).6 Phenytoin is a classic antiepileptic drug used
 Chemical      :  C15H12N2O2
 formula                                                                                            therapeutically as early as 1938.
 General       :  Phenytoin can cause a wide range of adverse idiosyncratic effects such as
 toxicity         cosmetic changes, blood dyscrasias, Stevens-Johnson syndrome and                  In many human studies, the duration of exposure to phenytoin and the
                  hepatotoxicity. The most common signs of toxicity of phenytoin are referable to
                                                                                                    dose levels used are not mentioned. Furthermore, (pregnant) epileptic
                  the central nervous system and are usually dose-related. At plasma drug
                  concentrations higher than 20 μg/ml drowsiness, dysarthria, tremor, ataxia and    women are very often treated with a combination of antiepileptic drugs,
                  cognitive difficulties were reported (Brodie, 1996).2
                                                                                                    making an evaluation of the effect of phenytoin on reproductive outcomes
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<pre>chapter 02 | Phenytoin                                                                                                           Phenytoin | page 12 of 81
more difficult. The assessment in this report is restricted to phenytoin   Taneja et al. (1994) evaluated the effect of seizures and phenytoin
exposure given as monotherapy.                                             monotherapy on the male reproductive system by studying seminal fluid.
                                                                           Three groups of men were included in this study: 42 epileptic men treated
2.3 Human studies                                                          with phenytoin, 13 untreated epileptic men and 28 control men
                                                                           (non-epileptic and untreated). After collection of semen, a minimum
2.3.1 Fertility studies                                                    number of 500-1,000 mature sperm cells was scored for morphologic
                                                                           abnormalities of head, neck, and tail. Serum samples of treated and
Male fertility                                                             untreated patients were analyzed for testosterone, luteinizing hormone
Herzog et al. (2006) compared serum levels of neuroactive steroids         (LH) and follicle-stimulating hormone (FSH), hormones influencing testis
among men with epilepsy who took various antiepileptic drugs, untreated    function. The treated and untreated epileptic patients showed no
men with epilepsy and non-epileptic controls. Twenty-five men with         difference in total seminal fluid volume, spermatozoa concentration, total
epilepsy who had been taking phenytoin only, ten men who had untreated     sperm count, or number of morphologically abnormal sperm. Both treated
epilepsy and 25 non-epileptic controls were included in the study. In      and untreated patients showed lower seminal fluid volumes (p<0.05) and
addition to serum analysis, sexual interest and function were assessed     spermatozoa concentrations (p<0.001) than the control group. In addition,
with a questionnaire. The phenytoin group had lower sexual interest and    the percentages of abnormal sperm were increased in untreated patients
function levels (p<0.001), lower serum dehydroepiandrosterone sulfate      (15.39±6.87; p<0.005) and in phenytoin-treated patients (12.77±7.17, not
(p<0.001), bioactive testosterone (p<0.001) and bioactive androstanediol   statistically significant) as compared to controls (9.47±4.04). Testosterone
(p<0.05) levels and a lower ratio of bioactive androstanediol to bioactive levels were lower than normal (<13 nM) in 4/9 untreated patients and 5/12
estradiol (p<0.05) compared to non-epileptic controls. The bioactive       phenytoin-treated patients. LH levels were increased (>9.8 IU/L) in 1/3
estradiol concentration was not different from the control group. The      untreated patients and 2/6 phenytoin-treated patients. According to the
untreated men with epilepsy had lower dehydroepiandrosterone sulfate       investigators, the results of this study are indicative for an indirect effect of
and bioactive androstanediol levels (both p<0.01) and a lower ratio of     epilepsy on the male reproductive function rather than a direct effect of
bioactive androstanediol to bioactive estradiol (p<0.05) compared to       phenytoin.8
non-epileptic controls.7
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<pre>chapter 02 | Phenytoin                                                                                                         Phenytoin | page 13 of 81
Chen et al. (1992) investigated the effects of phenytoin on sperm motility. Female fertility
Six epileptic patients treated with phenytoin monotherapy for at least five Morrell et al. (2005) investigated sexual dysfunction, sex steroid hormone
years (serum levels varied from 7.2 to 13.4 μg/ml) were observed for        abnormalities, and depression in women with epilepsy treated with
effects on sperm motility immediately after semen had liquefied or after a  antiepileptic drug monotherapy. Subjects were women with epilepsy
2-h pre-incubation at 37ºC (to detect effects on the duration of activity). receiving an antiepileptic drug in monotherapy for at least six months prior
Forty-five healthy volunteers served as control group. Sperm motility was   to study participation, as well as women without epilepsy not receiving
decreased in all treated patients when motility was measured immediately    antiepileptic drugs who served as controls. Thirteen epileptic women
after semen liquefication (22.9±11.7) or after a 2-h pre-incubation at 37ºC receiving phenytoin were included in the study, as well as thirteen
(13.5±8.7) compared to healthy donors (42.6±12.5 and 35.2±7.0               nonepileptic controls. All subjects were between the ages of eighteen and
respectively). In addition, the duration of sperm activity of epileptic     40, cycling, and at least four years postmenarche. Women with epilepsy
patients was shorter than that of the controls (p<0.05). The effect on      were recruited from the patient populations of two U.S. Epilepsy Centres.
sperm motility showed no correlation with duration of therapy, serum        Nonepileptic controls were recruited from friends and family of the
phenytoin levels or seizure types.9                                         participants. Subjects provided medication history and completed a
                                                                            reproductive history form and a seizure history form. Sexual function was
The in vitro experiment published by Chen et al. in 19929 but originally    determined by the subject’s response to sexual inventories examining
reported by Shen and Chen (1990) showed reduced sperm motility upon         sexual experience and attitude. The subjects also completed an internally
2-h pre-incubation with phenytoin concentrations 1.6, 4.2 and 5.0 mM,       developed questionnaire examining sexual desire and arousal to
compared to incubation medium (all p<0.01). The inhibitory effect on        determine whether a sexual dysfunction was present as defined by the
sperm motility appeared to be dependent on both duration of                 Diagnostic and Statistical Manual of Diseases Classification (4th Edition).
pre-incubation and the concentration of the drug.10                         Sexual dysfunction and sexual anxiety were higher and sexual arousal
                                                                            was lower than in controls (p<0.05).12
Hong et al. (1982) also measured the effects of phenytoin on human
sperm motility in vitro. Using concentrations as high as 2mM, phenytoin
did not have an effect on sperm motility.11
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<pre>chapter 02 | Phenytoin                                                                                                               Phenytoin | page 14 of 81
2.3.2 Developmental toxicity studies                                          malformed controls with other defects were included. There were 1,374
Treatment with phenytoin during pregnancy has been associated with a          cases of isolated cleft lip with or without cleft palate. Maternal phenytoin
distinct set of malformations called the foetal hydantoin syndrome            treatment was recorded by gestational month. Phenytoin use during the
(Hanson and Smith, 1975; Smith‘s Recognizable Patterns of Human               second and third months of pregnancy was evaluated. Phenytoin use in
Malformations, 2014).13,14 Among these developmental disturbances are         gestational months before and after the above period was not evaluated,
abnormal facial features, anomalies of the distal phalanges, pre- and         However, if pregnant women took phenytoin in the first gestational month
postnatal growth deficiency, as well as mental performance deficiency.        and continued to use it in the second, third and/or fourth months, these
Other defects reported less frequently include cleft lip and/or palate,       treatments were evaluated as well. The odds ratios (ORs) with 95%
cardiovascular anomalies, renal defects, positional limb deformities and      confidence intervals (CIs) were adjusted for maternal age and
diaphragmatic hernias. Clinicians generally consider phenytoin as a           employment status, parity and acute maternal disease in the second and/
teratogen. A drawback of most of the epidemiological studies this             or third months of pregnancy. Polytherapy was not mentioned as exclusion
conclusion is based upon, is that they concern pregnant women receiving       criterion. An increased risk of isolated cleft lip with or without cleft palate
combinations of phenytoin and other antiepileptic drugs (polytherapy). The    was shown for phenytoin (OR=3.0; 95% CI 1.5-5.8, compared to
Committee assesses the strength of the epidemiological evidence for the       population controls, and OR=4.4; 95% CI 2.1-9.1, compared to malformed
purpose of classification focused on data regarding monotherapy.              controls). The ORs for the comparison with population controls differed
                                                                              between mothers who used folic acid during the critical period (OR=2.3;
Structural defects                                                            95% CI 0.7-7.7) and mothers who did not (OR=3.6; 95% CI 1.6-8.0).15
Surveillance systems                                                          Arpino et al.. (2000) used an international database on congenital
Puhó et al. (2007) used the Hungarian Case-Control Surveillance of            malformations and drug exposure (MADRE) to assess the teratogenic
Congenital Abnormalities to investigate the developmental toxicity of all     effects of five antiepileptic drugs, one of them being phenytoin. Among
drugs used in at least 0.5% of pregnant women who later delivered             8,005 cases of congenital malformations, 24 infants had been exposed to
children with orofacial clefts. A total of 1,975 cases with orofacial clefts, phenytoin monotherapy during the first trimester of pregnancy. Cases
38,151 population-based controls (without birth defects) and 20,868           were defined as infants presenting with a specific malformation, and
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<pre>chapter 02 | Phenytoin                                                                                                           Phenytoin | page 15 of 81
controls as infants presenting with any other birth defect. Infants exposed exposed to specific antiepileptic drugs in monotherapy during the first
to drugs other than antiepileptic drugs were classified as nonexposed.      trimester of pregnancy and compared to an unexposed group. Women
ORs with 95% CIs were estimated for each of the nine contributing           were eligible for analysis if they had a liveborn infant, a stillborn infant, or
registries separately and combined. An association between phenytoin        a pregnancy terminated because of a foetal abnormality. They were
and a congenital malformation, i.e. spina bifida, was observed in only one  ineligible if they had a spontaneous abortion, withdrew from the registry, or
registry (two exposed cases; OR=62.33; 95% CI 4.9-785.9).16                 were lost to follow-up. Internal controls were pregnant women not taking
                                                                            an antiepileptic drug and without epilepsy who had been recruited among
Prospective studies                                                         the friends and relatives of antiepileptic drug-exposed participants since
Vajda et al. (2012) analysed prospectively collected data from the          2003. The phenytoin-exposed group consisted of 416, the control group of
Australian Pregnancy Register to provide information on the relative        442 subjects. In addition, an external control group of 206,224 infants was
teratogenicity of antiepileptic drugs. The database contained pregnancy     captured by a surveillance system at Brigham and Women’s Hospital in
outcomes from 1,317 women with epilepsy. Information on the duration of     Boston using the same inclusion and exclusion criteria for outcome
the prenatal exposure of the children was not provided. Whether the         definition. Twelve phenytoin-exposed infants had major malformations
exclusion criteria were those of EURAP, was not mentioned. Excluded         (2.9%; 95% CI 1.5-5.0) and five unexposed internal controls (1.1%; 95%
were pregnancies that ended in spontaneous abortions or chromosomal         CI 0.4-2.6), which led to a relative risk (RR) of 2.6 (95% CI 0.9-7.4).
or genetic abnormalities, those in which the women had treatment            Comparison with the external controls gave a similar result.18
changes in the first trimester, and those involving other diseases or
treatment that could affect foetal outcome. The prevalence of               Thomas et al. (2008) examined the prevalence of cardiac malformations
malformations associated with phenytoin monotherapy was 1/35 (2.9%).        and its association with antiepileptic drugs in a prospective study
Their prevalence in the untreated population was 6/106 (5.2%).17            evaluating several drugs as mono- or polytherapy, based on the Indian
                                                                            Kerala Registry of Epilepsy and Pregnancy. The evaluation concerned
Hernández-Diaz et al. (2012) examined the offspring of women who            740 pregnant women with epilepsy enrolled between April 1998 and
enrolled in the North American AED Pregnancy Registry between 1997          December 2004. Thirty-one infants were born from mothers treated with
and 2011. The risk of major malformations was calculated among infants      phenytoin monotherapy during the first trimester of pregnancy. At three
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<pre>chapter 02 | Phenytoin                                                                                                           Phenytoin | page 16 of 81
months of age, a cardiologist carried out a clinical examination and        convulsions during their pregnancy. Fifty-six children were exposed to
echocardiography on all live-born babies. None of the babies showed         phenytoin monotherapy during the first trimester of pregnancy. In 3.6%
cardiac malformations.19                                                    (2/56) foetal death was observed and in 7.1% (4/56) congenital
                                                                            malformations were seen. These congenital malformations were observed
Thomas et al. (2017) estimated the RR of major congenital malformations     in the brain (agenesis of corpus callosum), heart (ventricular septal defect)
in the offspring of 2,454 pregnant women with epilepsy enrolled in the      and genital region (hydronephrosis with extrarenal pelvis and
Kerala registry from 1 April 1998 until 31 December 2013. They evaluated    undescended testicle). Controls were not included in this study.21
the effects of prenatal exposure to various antiepileptic drugs as mono- or
polytherapy. One hundred and six children were born to mothers who          Morrow et al. (2006) studied the risk of major congenital malformation
received phenytoin monotherapy. Two control groups were included:           from in utero exposure to antiepileptic drugs. Prospective data collected
women with epilepsy not taking any antiepileptic drugs (n=252) and          by the UK Epilepsy and Pregnancy Register during the period 1996-2005
women without epilepsy in the first trimester of pregnancy and not using    were analysed. Included were 82 children born to women taking phenytoin
antiepileptic drugs, from an antenatal clinic (n=319). Their socioeconomic  as monotherapy and 239 children born to women with epilepsy but not
backgrounds were similar. The RR of major congenital malformations in       taking any antiepileptic drug, who served as controls. The investigators
the children exposed to phenytoin prenatally was not increased, compared    adjusted the data for the age at delivery, parity of the mother, family
to the offspring of women with epilepsy not using antiepileptic drugs       history of major congenital malformations, periconceptional folic acid
(RR=1.0; 95% CI 0.0-2.5), or the offspring of unexposed healthy women       exposure, and sex of the infant. The phenytoin-exposed children did not
(RR=1.6; 95% CI 0.6-4.3).20                                                 show a higher percentage of malformations than the controls. 22
Meador et al. (2006) investigated the foetal outcome after phenytoin        Holmes et al. (2001) investigated the presence of major malformations,
intake during pregnancy in a prospective study across 25 epilepsy           signs of hypoplasia of the midface and fingers, microcephaly and small
centres, aimed at comparison of four commonly used antiepileptic drugs.     body size in children born to women with epilepsy taking antiepileptic
In total, 354 mother/child pairs were included in the study. Most mothers   drugs at five American maternity hospitals from 1986 to 1993. Women
(81%) were seizure-free during pregnancy; only 3% had more than five        were excluded if they did not speak English, had a multiple-gestation
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<pre>chapter 02 | Phenytoin                                                                                                             Phenytoin | page 17 of 81
pregnancy, or had another potentially teratogenic factor, such as type 1       matched for gestational age, gender and mode of delivery. Four controls
diabetes mellitus. They completed questionnaires to provide demographic        were lost to follow-up. At the age of nine months, children exposed to
and medical data. Included were infants exposed to antiepileptic drugs         phenytoin in utero and unexposed children showed facial anomalies in
(n=316), as well as infants not exposed to antiepileptic drugs whose           2/21 vs 6/83 cases, digital anomalies in 2/21 vs 8/83, genital anomalies in
mother reported having had epilepsy (n=98). For each of these children,        0/21 vs 0/83, skin anomalies in 4/21 vs 9/83, and other anomalies in
a control was recruited from the ten infants born closest in time to him or    0/21 vs 2/83 cases, respectively).24
her (n=508). In 87 cases the exposed infants were born to mothers on
phenytoin monotherapy. The infants of mothers with a history of epilepsy       Kaneko et al. (1999) identified the major risk factors for the occurrence of
who had not taken antiepileptic drugs did not show more abnormalities          congenital malformations, the relative teratogenic risks of several
than the control infants, neither in term of individual outcomes, nor overall. antiepileptic drugs and advisable ranges of antiepileptic drug doses to
Compared to the controls, the phenytoin-exposed infants had a higher           reduce the risk of congenital malformations in offspring in a prospective
frequency of at least one of the following abnormalities: major                study. A total of 423 children were exposed to phenytoin in utero during at
malformations, microcephaly, growth retardation, midface hypoplasia and        least the first trimester at daily doses of 50 mg/day (3.0 μg/ml drug level).
hypoplasia of the fingers (OR=2.8; 95% CI 1.1-8.8).23                          A group of 98 children born to epileptic women not taking any antiepileptic
                                                                               drugs during gestation served as control. The children were examined for
Wide et al. (2000) assessed minor anomalies in infants exposed to              congenital malformations at birth, at five days and at one month of age.
antiepileptic drugs in utero in a population-based follow-up study of          Three controls had malformations (3.1%). The prevalence of
children born to women with epilepsy, treated during pregnancy, and            malformations in offspring exposed to phenytoin monotherapy (n=132)
enrolled from 1985 to 1995. Twenty-two women received phenytoin                was 9.1% (OR=3.2; 95% CI 0.9-11.5 (CI calculated by the Committee)).
monotherapy at a mean dose of 274 mg/day (range 75-450). They took             The types of malformation were not reported.25
the drug throughout pregnancy. Twenty-one exposed children were
examined for minor facial, digital, genital, skin and other anomalies. The     Canger et al. (1999) analysed the prevalence of malformations among
control group consisted of 87 unexposed children, born in the same             infants of mothers with epilepsy treated with antiepileptic drugs during
hospital within two days of the birth of a phenytoin-exposed child and         pregnancy. The first pregnancies of 517 women were studied
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<pre>chapter 02 | Phenytoin                                                                                                            Phenytoin | page 18 of 81
prospectively from December 1977 to 1996. Fifty-eight pregnancies that       previous abortions, an OR of 2.2 (95% CI 0.7-6.7) was observed, with
had ended in early spontaneous (n=38) or early elected (n=20) abortions      5 congenital malformations occurring among 33 phenytoin-exposed
were excluded from the analyses. Seven of the remaining pregnancies          pregnancies. The malformations observed among phenytoin-exposed
were lost to follow-up. Another eight ended in a therapeutic abortion due    infants were inguinal hernia, heart defects, cleft lip with or without cleft
to a malformation. Thirty-one of the remaining 444 pregnancies were in       palate, pre- or postaxial polydactyly, hypospadias, microcephaly, and
women receiving phenytoin monotherapy. No information on duration of         megacolon.27
treatment was given and no control group was included. The children born
to three of the women taking phenytoin as monotherapy, at 200 or 375         Koch et al. (1992) reviewed data on congenital malformations obtained in
mg/day, had malformations: one child had a club foot, one a hip              a collaborative study on epilepsy, antiepileptic drugs and pregnancy
dislocation, and one an umbilical hernia.26                                  outcome. The aim of the study was to clarify the role of antiepileptic drugs
                                                                             versus genetic predisposition and other confounding factors in the major
Samrén et al. (1997) pooled and reanalyzed data from five prospective        and minor anomalies observed at birth and at one and four years of age.
studies in Europe to quantify the risk of congenital malformations following Pregnant women with epilepsy treated with phenytoin monotherapy
intrauterine antiepileptic drug exposure in mono- and polytherapy. Data      (n=24), women with epilepsy without treatment (n=25) and women whose
were available for 1,221 children of which 141 were exposed to phenytoin     partners had epilepsy (n=22) were included in the study and matched with
in utero. A control group of 158 children of unexposed pregnancies among     healthy controls on socioeconomic status and maternal age, previous
non-epileptic women from Germany was included. The results showed an         abortions, parity, and smoking habits during the third trimester of
overall increased risk of major congenital abnormalities in children of      pregnancy. The duration of the prenatal exposure to phenytoin of the
mothers with epilepsy treated with anti-epileptic drugs during pregnancy     offspring was not reported. Two major malformations, a heart defect and a
as compared with children of healthy controls. The number of malformed       megacolon occurred in offspring of mothers with phenytoin monotherapy.
children after phenytoin monotherapy was 9/141 (6%), compared to             Specific minor anomalies more frequent in children exposed to phenytoin
12/158 (8%) among the nonexposed controls. When the analyses were            than in controls at one year of age were hypoplasia of the nails (n=6,
restricted to the exposed and unexposed pregnancies from Germany,            p<0.001) and hypoplasia of the phalanges (n=7, p<0.001). These
matched for maternal age, parity, social class, smoking habits and
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<pre>chapter 02 | Phenytoin                                                                                                                          Phenytoin | page 19 of 81
anomalies were less frequent at four years of age and in children of         polytherapy). The presence of nine minor craniofacial and digital features
untreated mothers with epilepsy and fathers with epilepsy.28                 was examined clinically. The effects of phenytoin mono- and polytherapy
                                                                             were not analysed separately. The in utero exposure duration was not
Oguni et al. (1992) investigated the prevalence of abnormal pregnancy        reported. Maternal phenytoin levels were measured. Moderate to high
outcomes in the offspring of 103 epileptic women who had 115                 (>40 μmol/L) phenytoin levels in the first 20 weeks of pregnancy were
pregnancies and were followed during pregnancy between 1982 and              associated with hypertelorism (RR=6.3; 95% CI 1.5-26.8), nail hypoplasia
1989. Ninety pregnancies had sufficient follow-up of the pregnancy           (RR=6.2; 95% CI 1.9-20.0), three or more dermal arches (RR=3.9; 95% CI
outcomes. Twelve women were included with more than one pregnancy            1.0-15.7), distal phalangeal hypoplasia (RR=11.9; 95% CI 3.7-38.8) and
each. Therapeutic abortions were excluded except when the reason for         digital hypoplasia combineda (RR=10.6; 95% CI 1.8-40.2).30
abortion was a foetal abnormality. Five epileptic women not receiving any
anticonvulsants served as controls. Twenty epileptic women received          Gaily (1990) studied the phalangeal and metacarpal bone length in
phenytoin monotherapy during the first trimester of pregnancy. Their         children from epileptic mothers (n=111) and in control children of
pregnancies led to spontaneous abortion in two cases, but not to any         nonepileptic mothers (n=96) as a follow-up. Gaily used radiological
babies with major malformations. There were no spontaneous abortions in      measurement of the degree of distal digital hypoplasia, a more discrete
the control group, nor babies with malformations.29                          and objective method than clinical examination. The mean age of both
                                                                             groups at the time of the examination was 5.5 years (range 5.2-5.8 years).
Gaily et al. (1988) reported the outcome of a prospective study in which     Seventy-six of the children born to epileptic mothers had been exposed in
121 children of epileptic mothers were examined at 5.5 years of age. A       utero to phenytoin, 21 to other anti-epileptic drugs and 14 had not been
control group of healthy children was included (n=105). Selection criteria   exposed to any anti-epileptic drug. Maternal phenytoin levels were
for inclusion in the control group were absence of maternal epilepsy or      measured at least once during the first 20 weeks of pregnancy. Phenytoin
other chronic disorder in the mother, absence of intrauterine drug           exposure during this period was associated with an elevated prevalence
exposure, gestational period at least 37 weeks, and no major perinatal       of radiologically defined distal phalangeal hypoplasia of mainly the second
illness or complication. Eighty-two of the 121 children of epileptic mothers
had been exposed to phenytoin in utero (46 to monotherapy and 36 to          a
                                                                               Nail/distal phalangeal hypoplasia and ≥ 3 dermal arches combined
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<pre>chapter 02 | Phenytoin                                                                                                                Phenytoin | page 20 of 81
and fifth digits (11% versus 1% among controls and not phenytoin-                 exposed to phenytoin monotherapy in utero, 15 were diagnosed with distal
exposed children, p<0.01). The eight children exposed to the highest              digital hypoplasia (in most cases in hands and feet) and five with minor
phenytoin levels (>40 µmol/L) showed the most prominent effects. Only             craniofacial abnormalities. One case of microcephaly and one with major
44 of the 76 women treated with phenytoin received no other antiepileptic         abnormality were also observed. A control group was not described.33
drugs. Separate results for this monotherapy group were not reported.31           As part of the study, hand radiographs were obtained on 51 children born
                                                                                  to epileptic mothers and phalanges and metacarpals were measured. The
D’Souza et al. (1990) studied the outcome among 22 children born to               results of these analyses were reported separately (Kelly, 1984).34 In 20
mothers treated with phenytoin as monotherapy during pregnancy in a               pregnancies phenytoin was taken during pregnancy at doses of 200-600
prospective study including 61 epileptic women. Maternal phenytoin levels         mg/day. Seven of the 20 children (35%) had distal digital hypoplasia.
were 10-25 mg/L. A control group, matched for maternal age, parity and
social class, without any medical complications and not taking any drugs          Follow-up studies of pharmacovigilance centre data
regularly (n=62), was included. Twelve of the 22 children exposed to              In a follow-up study of women reported to the Motherisk Program
phenytoin in utero throughout pregnancy had congenital anomalies versus           described by Gladstone et al. (1992), children exposed to phenytoin in
none of the controls. The congenital anomalies observed were: epicanthic          utero were investigated for major and minor anomalies. The study
folds, extra digits, heart disease, dislocation of hip, hypoplastic nails, distal included 16 women with epilepsy who had taken phenytoin during the first
phalangeal hypoplasia, hypospadias, ptosis, craniosynostosis and Down’s           trimester of pregnancy. Fifteen of them had taken phenytoin as
syndrome. One child that had been exposed to phenytoin during the first           monotherapy and one had taken a second anti-epileptic drug. The study
trimester of pregnancy only showed no anomalies.32                                included a matched control group (n=16) of women exposed to other
                                                                                  drugs without medical complications. Abnormalities observed among
Kelly et al. (1984) investigated the prevalence of abnormalities in the           phenytoin-exposed offspring were minor anomalies (3/16; flattened nasal
offspring until two years of age in a prospective study among mothers             bridge, nail hypoplasia, or absence of the distal phalanx in the right index
from low socioeconomic status with high frequency of tonic-clonic                 finger), adrenal haemorrhage (1/16) and developmental delay (1/16). One
generalized seizures and the use of anticonvulsants. The duration of the          elective abortion and one neonatal death, but no malformations occurred
in utero exposure of the children was not reported. Of the 41 children            in the control group. Statistics were not reported.35
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<pre>chapter 02 | Phenytoin                                                                                                         Phenytoin | page 21 of 81
In another study among women reported to the Motherisk Program,            controls had congenital malformations. The malformations in the exposed
Scolnik et al. (1994) investigated children exposed in utero to phenytoin  children were clubfoot, hypospadias and missing distal phalanx of the right
monotherapy for the presence of major malformations. Thirty-four women     index finger. Minor anomalies, in particular high forehead, frontal bossing,
exposed to phenytoin were matched with controls exposed to other drugs.    malar hypoplasia, toe-finger-nail dysplasia and epicanthal folds, were
These women came in for counselling after exposure to other drugs.         observed more frequently among exposed children compared to controls
Other matching criteria were age, gravidity, parity, and socioeconomic     (overall RR= 2.1, p<0.01). 37 It is unclear whether this study includes the
class. Two phenytoin-exposed infants showed major malformations, one       women reported about by Gladstone et al.35
of them having cleft palate and hypospadias, the other demonstrating
meningomyelocele and hydrocephalus. None of the control children           Retrospective cohort studies
showed major malformations.36 It is unclear whether this study includes    Adab et al. (2004) performed a retrospective cohort study in 249 children
the women reported about by Gladstone et al.35                             aged six months to sixteen years and exposed to antiepileptic drugs in
                                                                           utero. An unexposed control group consisted of 101 children, 83 of them
In a third follow-up study of women reported to the Motherisk Program,     aged six years or older (10.5±3.2 years) and eighteen up to five years of
Nulman et al. (1997), investigated the effects of phenytoin monotherapy in age (3.3±0.9 years). A clinician conducted semi-structured interviews of
the treatment of maternal epilepsy and separated them from those of        the epileptic mothers to ascertain information about their epilepsy and
epilepsy itself. The study comprised a group of pregnant women with        relevant pregnancy. Clinical records were used to confirm this information.
epilepsy treated with phenytoin (n=29), a group of pregnant epileptic      The interviews were also used to collect data for each child on early
women not treated with phenytoin (n=9) and a group of pregnant women       development, behavioural problems, schooling, additional educational
treated with phenytoin for conditions other than epilepsy (n=5), all       needs, and the need for additonal therapy including speech therapy. The
matched to women who came in for counselling after exposure to other       children were examined for dysmorphic features, defined as cosmetic
drugs (n=34). Other matching criteria were age, gravidity, parity, and     variations without disability, and major malformations, defined as structural
socioeconomic class. The phenytoin-using women took the medicine           abnormalities requiring medical or surgical intervention to prevent
throughout pregnancy. Three out of 34 children exposed to phenytoin in     disability, using the EUROCAT guidelines. Twenty-one children aged six
utero (born from epileptic and non-epileptic mothers) and two out of 34    years or older (10.7±3.5 years) and five children up to five years of age
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<pre>chapter 02 | Phenytoin                                                                                                          Phenytoin | page 22 of 81
(2.6±1.4 years) were exposed to phenytoin monotherapy in utero. The          frequencies of neonatal withdrawal, congenital malformations, childhood
duration of the prenatal exposure was not reported. The frequencies of       medical problems, developmental delay and behavioural disorders in the
dysmorphic features and major malformations were either incompletely or      offspring of 149 women who took antiepileptic drugs during pregnancy
not reported. The only results reported were that phenytoin-exposed          and delivered between 1976 and 2000. They were identified through
children aged six years or older did not have more dysmorphic features       review of hospital records, or recruited from the antenatal clinic and
than the controls (no statistical details mentioned). The other data from    postnatal wards. A structured interview including pregnancy histories and
the study are reported in the section Functional and cognitive effects. 38   standardised assessment of all available offspring was carried out by a
                                                                             trained research nurse. Thirty-eight siblings of exposed cases were not
Orup et al. (2003) identified skeletal deviations in children after prenatal exposed to antiepileptic drugs in utero. They served as controls. In 16
exposure to the anticonvulsant phenytoin. The study comprised 28             cases the mother had epilepsy but took no treatment and in 22 cases the
children of which seven children were exposed to phenytoin as                child was born before epilepsy developed. Twenty-four children that had
monotherapy. The exposure lasted the entire nine months of pregnancy.        been exposed to phenytoin as single antiepileptic drug were identified.
The children exposed to phenytoin monotherapy were examined at five to       They had a mean age of 11 years at the time of study. The mean age of
14 years of age. Craniofacial structures, hand-wrist structures and dental   the controls was 15 years. The phenytoin-exposed children demonstrated
maturity were evaluated. Normative data from several sources served as       increased frequencies of minor congenital malformations and either major
reference populations for comparative purposes. Deviations in drug-          congenital malformation or developmental delay, as compared to the
exposed children as compared to controls were decreased lengths of the       controls (p<0.05). The neurodevelopment and behaviour findings are
maxilla and mandible, several dental changes, decreased face height and      reported in the section Functional and cognitive effects.40
decreased nasal bone length and bone angle (p<0.01 to p<0.0001).
Deviations, especially in the maxilla, persisted with age (unclear whether   Lu et al. (2000) investigated whether digit anomalies, associated with in
this observation applies to phenytoin monotherapy) 39                        utero exposure to antiepileptic drugs, could be better identified using
                                                                             radiographs and dermatoglyphics rather than relying only on visual
Dean et al. (2002) examined the neonatal and later childhood morbidity in    inspection. Forty-six antiepileptic-exposed individuals were examined of
children exposed to antiepileptic drugs prenatally. They investigated the    which 13 children were exposed to phenytoin monotherapy. An unexposed
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<pre>chapter 02 | Phenytoin                                                                                                          Phenytoin | page 23 of 81
control group (n=75) was included. This group consisted of (1) children     twenty-one women were using one or multiple antiepileptic drugs during at
recruited from the same sources as the phenytoin group, (2) children of     least the first trimester of pregnancy (1,411 children were exposed in
families enrolled in a large health maintenance organization and (3)        utero). One thousand nine hundred fifty-five nonexposed control women
children whose previous radiographs were used for a subjective analysis     (2000 children) were included in this study. Matching criteria were age and
of the qualitative changes in comparison to those in antiepileptic drug-    parity of the mother, and sex, birth year and hospital of delivery of the
exposed children and who were not growth retarded, and did not have         child. One-hundred fifty-one women were treated with phenytoin as
either a serious medical disorder or exposure in utero to anti-epileptic    monotherapy. One child (1%) had major congenital abnormalities (type of
drugs. The age range was only reported for monotherapy-exposed and          defect was not mentioned). Statistical analysis showed no excess risk (RR
polytherapy-exposed children combined. The evaluation included:             0.5; 95% CI 0.1-3.4).42
physical examination of the fingers, nail size, dermal ridge patterns,
measurements of phalanges and metacarpals, qualitative assessment of        Meta-analyses
radiographs and interrelationships. Information as to the duration of the   Weston et al. (2016) carried out a meta-analysis to assess the effects of
prenatal exposure to phenytoin was not provided. Nail size was not          prenatal exposure to antiepileptic drugs on the prevalence of congenital
decreased in phenytoin-exposed children compared to controls (60 out of     malformations in the child. They included prospective cohort studies,
the 75, selection criteria not specified). Three or more arched fingerprint cohort studies set within pregnancy registries and randomised controlled
patterns in ten fingers occurred at a frequency of 14.4% in children        trials. Participants were women with epilepsy taking antiepileptic drugs;
exposed to phenytoin monotherapy as compared to 1.3% in controls,           the two control groups were women without epilepsy and women with
p<0.0005). Data on other digit changes were not reported for the group      epilepsy who were not taking antiepileptic drugs during pregnancy. The
exposed to phenytoin monotherapy.41                                         primary outcome was the presence of a major congenital malformation.
                                                                            Secondary outcomes included specific types of major congenital
Samrén et al. (1999) performed a large retrospective cohort study to        malformations. Thirty-one studies, on a variety of antiepileptic drugs,
assess the risk of major congenital abnormalities associated with           contributed to the meta-analysis. Children born to epileptic women
antiepileptic drugs. The study comprised offspring of women with epilepsy,  receiving phenytoin monotherapy were at an increased risk of congenital
with or without antiepileptic drug use during pregnancy. Nine hundred       malformation compared with children born to women without epilepsy (five
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<pre>chapter 02 | Phenytoin                                                                                                            Phenytoin | page 24 of 81
studies; n=477 vs 987; RR 2.38; 95% CI 1.12-5.03) and to women with          malformations than control (OR=1.67; 95% CI 1.30-2.17). It was also
untreated epilepsy (15 studies; n=640 vs 1,256; RR=2.40; 95% CI 1.42-        associated with two types of specific malformation: cleft lip/palate
4.08). The malformations noted were neural tube, cardiac, oro-facial/        (OR=3.11; 95% CI 1.31-7.72), and club foot (OR=2.73; 95% CI 1.13-6.18).
craniofacial and skeletal/limb defects.43                                    Phenytoin monotherapy was not associated with an increased risk of
                                                                             cardiac malformation, hypospadias, inguinal hernia, or undescended
Veroniki et al. (2017) conducted a systematic review and network meta-       testes, nor with an increased risk of foetal loss, prenatal growth
analysis of congenital malformations and prenatal outcomes of                retardation, preterm birth, or any minor congenital malformations.44
pregnancies of women receiving antiepileptic drugs for any indication.
Included were monotherapy and polytherapy. The comparators were              Growth
placebo, no antiepileptic treatment (women not exposed to any
antiepileptic drug, but with the same indications for use), or other         Prospective studies
antiepileptic drugs alone or in combination. The primary outcomes were       Arulmozhi et al. (2006) evaluated the physical growth and psychomotor
the prevalence of overall and specific types of major congenital             development of infants exposed to antiepileptic drugs in utero in a
malformation. When studies also reported on major congenital                 prospective study of 30 pregnant women. Eighteen women exposed to
malformation cases that were diagnosed prenatally and resulted in            phenytoin monotherapy (200-300 mg/day) throughout pregnancy were
elective terminations, these were included in the congenital malformation    included in this study. A control group (n=30) was included, matched for
analysis. For specific types of congenital malformation, the six most        socioeconomic status, education of the parents and nutritional status of
frequently occurring in the literature were selected, namely cardiac defect, the mothers. The mothers were interviewed regarding the feeding pattern
cleft lip/palate, club foot, hypospadias, inguinal hernia and undescended    of the child – whether breastfed or started on supplementary feeds and
testes (boys only). The secondary outcomes of interest were foetal loss,     intercurrent illness if any was noted. The physical growth of the babies
prenatal growth retardation, preterm birth, and minor congenital             was examined at birth and at the 1st, 6th, and 12th month of age. It was
malformations. The investigators included 92 cohort studies, three case-     assessed by measuring the body weight, head circumference, length and
control studies, and one randomised clinical trial. Phenytoin monotherapy    anterior fontanelle. The body weight, head circumference and length of
was associated with a higher risk of developing major congenital             the case and control babies did not differ at birth and at one month of age.
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<pre>chapter 02 | Phenytoin                                                                                                           Phenytoin | page 25 of 81
At six and 12 months of age, the case babies had a lower body weight         received phenytoin monotherapy, but its duration was not mentioned.
and a smaller head circumference, and they were shorter than the             Phenytoin exposure did not cause any change in offspring body weight,
controls (p<0.01 or p<0.001). Phenytoin monotherapy was associated with      body length, or head circumference compared to unexposed controls.47
a larger area of the anterior fontanelle at birth and at 12 months of age
(p<0.001). The data on psychomotor development of the babies are             Retrospective cohort studies
reported in the section Functional and cognitive effects.45                  Artama et al. (2013) examined the effect of antiepileptic drug use during
                                                                             pregnancy on perinatal health in offspring in a nationwide, retrospective
Gaily and Granström (1989) investigated the delay of early postnatal         cohort study in Finland. This register-based study was based on all
physical growth and intelligence in drug-exposed children of epileptic       pregnancies ending in birth in Finland between 1996 and 2008. The
mothers. Forty-eight women on phenytoin monotherapy during pregnancy         outcomes included preterm birth, low birth weight, weight for gestational
(duration not reported) and 103 control children were included in this       age, low Apgar score, need for respiratory treatment, perinatal death and
study. The control children were born to non-epileptic mothers at the same   infant death. The data concern 751,139 singleton births. In cases with
hospital during the study period. The sampling criteria for the control      conflicting or missing information, the register data were confirmed and
children were gestation of at least 37 weeks, no major pre- or perinatal     supplemented with information from the maternity hospital records.
complication, and no drug exposure. Crown-heel length and weight was         Maternal age at delivery, parity, maternal residence district, socioeconomic
routinely measured up to 18 months of age. There was no evidence of          status and offspring major congenital anomalies were included in the
intrauterine phenytoin exposure causing growth retardation, indicated by     analyses as potential confounding factors. Twenty-six infants were born to
length or weight increments in the first postnatal month. The intelligence   epileptic women receiving phenytoin monotherapy one month prior to and/
findings are reported in the section Functional and cognitive effects.46     or during pregnancy. The controls were 721,948 women without epilepsy
                                                                             or antiepileptic drug use and their singleton offspring. All 26 children were
Hiilesmaa et al. (1981) studied foetal growth retardation in babies born to  born alive, 21 of them full term. The OR for preterm birth) was 1.85 (95%
133 epileptic mothers on antiepileptic medication. After delivery, a control CI 0.43-7.88), for low birth weight 1.33 (0.18-9.92), for large-for-
pair (mother and child) matched for maternal age, parity, social class, and  gestational-age 3.23 (0.96-10.83). The outcome small-for-gestational-age
foetal sex was selected for each epileptic woman. Fifty-five women           was not assessed. None of the 21 infants in the phenytoin-exposed group
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<pre>chapter 02 | Phenytoin                                                                                                            Phenytoin | page 26 of 81
that were born full term had a low Apgar score or neonatal respiratory       December 2001. The investigators selected 149 age- and sex-matched
problems needing treatment.48                                                controls from among the children attending two nearby schools in order to
                                                                             avoid any socioeconomic bias. Eleven children exposed to phenytoin
Functional and cognitive effects                                             prenatally were included in the study. Only the full scale IQ (measured
                                                                             with the Wechsler Intelligence Scale for Children, fourth edition) was
Prospective studies                                                          reported for this group separately. The full scale IQ of the phenytoin-
Thomas et al. (2008) investigated the motor and mental development of        exposed children was 82.6±13.5 (mean±SD) and that of the controls
infants exposed to antiepileptic drugs in utero. They evaluated the          80.7±13.7.50
offspring of 395 women enrolled in the Indian Kerala Registry of Epilepsy
and Pregnancy between 1998 and 2004. Twenty-nine infants from                Meador et al. (2011) examined dose-related effects of foetal antiepileptic
mothers receiving phenytoin monotherapy at any time during pregnancy         drug exposure on verbal and non-verbal cognitive measures at the age of
were included in the study. Thirty-two infants born to epileptic mothers not three years as part of a prospective multi-centre study. A control group
prenatally exposed to any antiepileptic drug served as controls. The         was not included in the study and the duration of the foetal exposure to
Mental Developmental Quotient and Motor Developmental Quotient of the        the drugs was not mentioned. Forty-one children were exposed to
infants were measured at 12 months of age. The Mental Development            phenytoin monotherapy during pregnancy at an average daily dose of 401
Quotient of the phenytoin-exposed infants was 90.3 (95% CI 77.3-103.3)       mg (range 67-750). Their cognitive performance was measured using the
and that of the controls 92.3 (95% CI 81.4-103.2). The Motor                 Differential Ability Scales, Preschool Language Scale (fourth edition),
Developmental Quotients of these groups were 100 (95% CI 91.6-108.4)         Peabody Picture Vocabulary Test (fourth edition) and Developmental Test
and 94.7 (95% CI 84.9-104.5), respectively.49                                of Visual-Motor Integration (fifth edition). Testing was conducted at 36-45
                                                                             months of age; standardized scores were calculated. The verbal index
Gopinath et al. (2015) further followed up this cohort when the children     was 95.9 (95% CI 91.0-100.8), the non-verbal index 102.0 (95% CI 96.9-
were between ten and 12 years of age. They studied IQ, attention,            107.2). Partial Pearson correlation for verbal and non-verbal indices to
memory and other neuropsychological functions in the 190 children            pregnancy average standardized dose, controlling for maternal IQ, were
completing the study and whose mothers enrolled between April 1998 and       0.09 and -0.20, respectively. No dose-related effects were seen.51
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<pre>chapter 02 | Phenytoin                                                                                                         Phenytoin | page 27 of 81
Arulmozhi et al. (2006) evaluated the physical growth and psychomotor      the drug throughout pregnancy. Twenty-one exposed children were tested
development of infants exposed to antiepileptic drugs in utero in a        with the Griffiths test for psychomotor development, which consisted of the
prospective study of 30 pregnant women. Eighteen women exposed to          subsets: gross motor function, personal and social behaviour, hearing and
phenytoin monotherapy (200-300 mg/day) throughout pregnancy were           speech, eye and hand coordination, and performance. The control group
included in this study. A control group (n=30) was included, matched for   consisted of 87 unexposed children, born in the same hospital within two
socioeconomic status, education of the parents and nutritional status of   days of the birth of a phenytoin-exposed child and matched for gestational
the mothers. The mothers were interviewed regarding the feeding pattern    age, gender and mode of delivery. At the age of nine months children
of the child – whether breastfed or started on supplementary feeds and     exposed to phenytoin in utero showed a mean total score in the Griffiths
intercurrent illness if any was noted. The data on the physical growth of  test that was similar to that of unexposed children (346 versus 344; 95%
the babies are reported in the section Growth. The psychomotor             CI for difference of the mean: -7.1 to 11.3).24
development of the babies was examined at the 2nd, 6th, and 12th month of
age. It was assessed using the Griffiths scales and babies were examined   Wide et al. (2002) also assessed the psychomotor development of the
for locomotor score, reaching behaviour and personal-social development.   children at the preschool age of 4.5-5 years. Follow-up at this age was
Phenytoin monotherapy was associated with a delayed locomotor              started in 1992. At that time, the children born in 1985-1986 were too old
development at the 2nd, 6th and 12th month, indicated by a negative impact to be included. Sixteen women were exposed to phenytoin monotherapy
on sitting progression (compared to controls, p<0.001). The reaching       at a mean dose of 253 mg/day (range 75-450), throughout pregnancy.
behaviour and the personal-social scores of the phenytoin-exposed          Fifteen exposed children were tested with the Griffiths test for
babies did not differ from those of the controls.45                        psychomotor development, which consisted of the subsets: locomotor
                                                                           function, personal and social behaviour, hearing and speech, eye and
Wide et al. (2000) assessed the psychomotor development in infants         hand coordination, performance, and practical reasoning. The control
exposed to antiepileptic drugs in utero in a population-based follow-up    group consisted of 66 unexposed children, matched for gestational age,
study of children born to women with epilepsy, treated during pregnancy,   gender and mode of delivery, recruited within ±2 days of the birth of a
and enrolled from 1985 to 1995. Twenty-two women received phenytoin        phenytoin-exposed child. At the age of 4.5-5 years children exposed to
monotherapy at a mean dose of 274 mg/day (range 75-450). They took         phenytoin in utero showed a reduction in mean scores for locomotor
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<pre>chapter 02 | Phenytoin                                                                                                           Phenytoin | page 28 of 81
development compared with unexposed children (98 versus 106; 95% CI           during the first 20 weeks of pregnancy. One hundred twenty-one of the
for difference of the mean: -14.0 to -0.4). The performance in the other      148 children were examined together with the control group at the age of
subsets of the test was not affected.52                                       5.5 years. The intelligence of 117 exposed and 104 control children was
                                                                              assessed by both verbal (Wechsler Preschool and Primary Scale of
Gaily and Granström (1989) investigated delay of early postnatal physical     Intelligence) and nonverbal (Leiter International Performance Scale)
growth and intelligence in drug-exposed children of epileptic mothers.        methods. Of the exposed children, 103 had been exposed in utero to
Forty-eight women on phenytoin monotherapy during pregnancy (duration         phenytoin, 54 of which to this drug as monotherapy. The results of children
not reported) and 103 control children were included in this study. The       exposed in utero to mono- or polytherapy were not analysed separately.
control children were born to non-epileptic mothers at the same hospital      The intelligence scores of the treated and control groups did not differ.53
during the study period. The sampling criteria for the control children were
gestation of at least 37 weeks, no major pre- or perinatal complication,      Follow-up study of pharmacovigilance centre data
and no drug exposure. The data on physical growth of the children are         Scolnik et al. (1994) investigated the neurodevelopment of children
reported in the section Growth. Intelligence was assessed at 5.5 years by     exposed in utero to phenytoin monotherapy in a study among women
a verbal (Wechsler Preschool and Primary Scale of Intelligence) and a         reported to the Motherisk Program. Thirty-four women exposed to
non-verbal (Leiter International Performance Scale) method. There was         phenytoin were matched with controls. These women came in for
no evidence of intrauterine phenytoin exposure affecting intelligence.46      counselling after exposure to other drugs. Other matching criteria were
                                                                              age, gravidity, parity, and socioeconomic class. All 34 women were treated
Gaily et al. (1988) investigated the intellectual performance of 148 children with phenytoin during the first trimester; 29 women took phenytoin
of epileptic mothers enrolled in a prospective study during pregnancy, and    throughout pregnancy. Complete physical and neurologic examination of
of 105 control children. Control selection criteria were absence of maternal  the children was performed, followed by neurobehavioral testing of both
epilepsy or other chronic disorder in the mother, absence of intrauterine     mothers and offspring. Children between 18 and 30 months of age were
drug exposure, gestational period at least 37 weeks, and no major             tested by means of the Bayley scales of infant development (1969) and
perinatal illness or complication. One hundred twenty-nine out of the 148     children beyond that age with the McCarthy scales (1972). All children
children born to epileptic mothers had been exposed to antiepileptic drugs    were also tested with the Reynell developmental language scales (1977).
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<pre>chapter 02 | Phenytoin                                                                                                        Phenytoin | page 29 of 81
Children exposed to phenytoin had lower (mean±SD) scores of global IQ     The ORs for ‘passed with excellence’ were 0.76 (0.59-1.07); 0.82 (0.62-
(103±25.2) than their controls (113.4±13.1) (p<0.05). Additionally, the   1.07); 0.92 (0.70-1.20) and 0.95 (0.73-1.24) for the four subjects. There
children exposed to phenytoin scored lower on the Reynell developmental   was no increased risk of leaving compulsory school without a final grade
language scales for verbal comprehension (0.2±1.6 versus control value    (OR=1.19 (0.79-1.80).54
of 1.1±0.95) and expressive language (-0.47±1.2 versus control value of
0.2±0.96) (p<0.05).36                                                     Adab et al. (2004) reported similar findings in a retrospective cohort study
                                                                          performed in 249 children aged six months to sixteen years and exposed
Retrospective cohort studies                                              to antiepileptic drugs in utero. An unexposed control group consisted of
Forsberg et al. (2011) studied children’s school grades at age sixteen in 101 children, 83 of them aged six years or older (10.5±3.2 years) and
order to evaluate long-term effects on neurodevelopment in children born  eighteen up to five years of age (3.3±0.9 years). A clinician conducted
to women with epilepsy during pregnancy. The Patient Register, the        semi-structured interviews of the epileptic mothers to ascertain information
Medical Birth Register, and a local study at a Stockholm hospital were    about their epilepsy and relevant pregnancy. Clinical records were used to
used to identify women with epilepsy in Sweden who had given birth        confirm this information. Twenty-one children aged six years or older
between 1973 and 1986. Exposed children were compared to all other        (10.7±3.5 years) and five children up to five years of age (2.6±1.4 years)
children born in Sweden between 1973 and 1986. The analysis was           were exposed to phenytoin monotherapy in utero. The duration of the
adjusted for child’s year of birth, maternal age, parity and maternal     prenatal exposure was not reported. The 21 phenytoin-exposed children
education level. Among the 1,070 children in this study, 429 had been     aged six or older were tested for verbal IQ, performance IQ and fullscale
exposed to anticonvulsants in polytherapy and 316 to phenytoin            IQ using the Wechsler IntelligenceTest for Children III. Eighty of the 83
monotherapy. The duration of the prenatal exposure was not reported.      unexposed children over 6 years of age served as controls. Verbal IQ in
The ORs with 95% CIs for ‘not passed’ and ‘passed in excellence’ in       the phenytoin group (mean 98.5; 95% CI 90.6-106.4) was not different
sports, mathematics, English and Swedish were measured. The ORs for       from that in unexposed control children from epileptic mothers (90.9; 95%
‘not passed’ were 1.00 (95% CI 0.68-1.47); 1.13 (0.81-1.54); 1.16 (0.81-  CI 87.2-94.6). Neither were performance IQ (mean 97.1; 95% CI 91.7-
1.66) and 1.17 (0.81-1.69) for sports, mathematics, English and Swedish,  102.6 vs 90.2; 95% CI 86.1-93.0) and full scale IQ (mean 97.6; 95% CI
respectively, for the children exposed to phenytoin monotherapy in utero. 90.3-105.0 vs 89.5; 95% CI 85.5-93.4). Educational problems (indicated
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<pre>chapter 02 | Phenytoin                                                                                                         Phenytoin | page 30 of 81
by the presence of additional educational needs, that were not specified    19.2%, for adaptability 7.7% vs 13.5%, for reinforces-parent 30.8% vs
any further) were assessed in children aged four and above. These           48.1%, for being demanding 7.7% vs 26.9%, for mood 46.2% vs 42.3%,
problems occurred in one (4.5%) of the phenytoin-exposed children and in    for acceptability 0% vs 25.0%, and for total domains 15.4% vs 25.0%.55
seven (8%) of the unexposed children. The OR for additional educational
needs was 0.98 (95% CI 0.36-2.68).38                                        Dean et al. (2002) examined the neonatal and later childhood morbidity in
                                                                            children exposed to antiepileptic drugs prenatally. They investigated the
Vinten et al. (2009) analysed the behaviour of children aged between six    frequencies of neonatal withdrawal, congenital malformations, childhood
and sixteen from the above cohort who had undergone a full                  medical problems, developmental delay and behaviour disorders in the
neuropsychological assessment and whose mothers had completed the           offspring of 149 women who took antiepileptic drugs during pregnancy
Vineland Adaptive Behavior Scales (VABS). Women and their children          and delivered between 1976 and 2000. They were identified through
were excluded from the study if they had a progressive neurological         review of hospital records, or recruited from the antenatal clinic and
deficit, a major learning difficulty, or symptomatic generalized epilepsy.  postnatal wards. A structured interview including pregnancy histories and
A total of 150 mothers completed the VABS regarding 242 children. The       standardised assessment of all available offspring was carried out by a
mothers were also asked to complete the Parenting Stress Index (PSI).       trained research nurse. Thirty-eight siblings of exposed cases were not
The VABS measures communication, daily living skills and socialization      exposed to antiepileptic drugs in utero. They served as controls. In sixteen
skills, while the PSI assesses the behavioural and temperament qualities    cases, the mother had epilepsy but took no treatment and in 22 cases the
of the child. Twenty children were exposed to phenytoin monotherapy in      child was born before epilepsy developed. Twenty-four children that had
utero, whereas 80 children were not exposed to any antiepileptic drugs in   been exposed to phenytoin as single antiepileptic drug were identified.
utero, although their mothers had a diagnosis of epilepsy. The data were    They had a mean age of 11 years at the time of the study. The mean age
adjusted for maternal and child IQ. The exposed children showed no          of the controls was 15 years. The phenytoin-exposed children did not
statistically significant effects in the VABS compared to the controls. PSI have a higher frequency of speech delay, motor delay, or behaviour
data were available from 13 phenytoin cases and 52 controls. The            disorders. The structural defect findings are reported in the section
percentages of exposed children versus controls falling within the highest  Structural defects.40
stress ranges for the domains of the PSI were: for distractibility 7.7% vs
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<pre>chapter 02 | Phenytoin                                                                                                           Phenytoin | page 31 of 81
Meta-analysis                                                               2.3.3 Lactation
Veroniki et al. (2017) conducted a systematic review and network meta-
analysis to compare the safety of antiepileptic drugs for neurodevelopment  Effects via lactation
of infants exposed in utero and/or during breast feeding. Randomized        Meador et al. (2010) investigated the effect of breastfeeding during
clinical trials, quasi-randomised clinical trials and observational studies phenytoin monotherapy on subsequent cognitive abilities in children in a
were eligible. Included studies assessed infants or children ≤ 12 years of  prospective multicentre observational study. They used the Differential
age whose mothers used antiepileptic drugs during pregnancy and/or          Ability Scales method to measure the children’s cognitive abilities. A
while breast feeding. Both monotherapy and polytherapy antiepileptic        nonexposed control group was not included. Mothers with an IQ below 70
drugs were eligible. Placebo, no antiepileptic drug treatment, or other     were excluded to avoid floor effects and because maternal IQ was
antiepileptic drugs alone or in combination were considered as              considered the major predictor of child IQ in population studies. Other
comparators. The primary neurological outcomes were cognitive               exclusion criteria included positive syphilis or HIV serology, progressive
developmental delay and autism/dyspraxia, and the secondary outcomes        cerebral disease, other major diseases (e.g., diabetes), exposure to
included attention-deficit hyperactivity disorder, language delay, neonatal teratogenic agents other than antiepileptic drugs, poor antiepileptic drug
seizures, psychomotor developmental delay and social impairment. The        compliance, drug abuse in the prior year, or drug abuse sequelae. At the
investigators included 29 cohort studies (5,100 patients). Phenytoin        age of three years the IQ of children breastfed (n=17) and non-breastfed
monotherapy during pregnancy and/or breast feeding was not associated       (n=23) was measured. The mean IQ for breastfed children, 91 (95% CI
with cognitive developmental delay, autism/dyspraxia, neonatal seizure,     84-98), was reported not to differ from the mean IQ for non-breastfed
psychomotor developmental delay, or attention-deficit hyperactivity         children, 99 (95% CI 93-105).57
disorder in the child. Adequate data on its effects on language delay and
social impairment were not available.56                                     Meador et al. (2014) also investigated the effect of breastfeeding during
                                                                            phenytoin monotherapy on subsequent cognitive abilities in children after
                                                                            a period of three more years. All mothers in the study continued taking the
                                                                            drug after delivery. At the age of six the IQ of children breastfed (n=17)
                                                                            and non-breastfed (n=20) was measured using the same method. The
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<pre>chapter 02 | Phenytoin                                                                                                         Phenytoin | page 32 of 81
former had a mean IQ of 104 (95% CI 99-110), the latter a mean IQ of 108    The mean plasma concentrations in two of the infants were 0.18 and
(95% CI 103-113), values that were reported not to differ.58                0.12 µg/ml. They were below the detection level in the remaining four.
                                                                            Assuming a total daily milk intake of 160 ml/kg bw, the investigators
Transfer via lactation                                                      calculated that the daily dose to the infant would vary between 0.03 to
Shimoyama et al. (1998) determined the concentrations of phenytoin in       0.47 mg/kg bw.61
breast milk and plasma samples from five lactating women. These women
had been treated with 100 (n=1), or 300 mg (n=5) phenytoin/kg bw/d. The     Kaneko et al. (1979) analysed the concentrations of phenytoin in serum
investigators reported an average milk to maternal plasma ratio of 0.289,   and breast milk of nine phenytoin-treated women with epilepsy at
with ratios ranging from 0.13 to 0.52 (13-52%).                             postnatal days 3-32. The dose of phenytoin they received was not
The concentrations in breast milk ranged between 0.41 and 1.30 µg/ml.       reported, but the concentration in their serum was 4.5±1.4 µg/ml and the
The authors calculated that a 4-kg infant drinking 1L of milk daily would   concentration in their milk 0.8±0.3 µg/ml. The milk to serum ratio was
ingest approximately 0.1-0.33 mg phenytoin/kg bw/d when the standard        18±6%.62
dose was administered.59
                                                                            Rane et al. (1974) analysed the transfer of phenytoin from mother to child
Fleishaker et al. (1987) analysed the phenytoin concentration in breast     in seven pairs of mothers taking phenytoin therapy and their newborn
milk and plasma samples from four lactating women. They reported a milk     children. The mothers took 200-500 mg/day, with or without additional
to plasma concentration ratio of 0.34±0.09 (34±9%).60                       medicines. Their plasma concentrations ranged from 0.7 to 15 µg/ml
                                                                            phenytoin at 0.03-3.6 hours before delivery. The first observed plasma
Steen et al. (1982) examined the milk to plasma concentration ratios of six concentrations in the newborn infants were between 0.43 and 13 µg/ml
women receiving phenytoin at a daily dose of 200, 300 or 400 mg. They       (blood samples taken 0 to 48 hours after birth). The amount of breast milk
also analysed the plasma concentrations of their infants. The study was     given to the infants was reported. The concentration of phenytoin in the
carried out between one and three months after delivery. The mean           milk was measured and reported in only one case. The breast milk of that
plasma phenytoin concentrations of the six mothers ranged from 3.2 to       mother contained 0.26-0.38 µg/ml, and the corresponding milk to maternal
19.8 µg/ml. The milk to plasma concentration ratios ranged from 6 to 18%.   plasma ratio was 45%. The plasma levels of the infants were measured
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<pre>chapter 02 | Phenytoin                                                                                                          Phenytoin | page 33 of 81
daily during the first week after birth. The data show that the plasma     2.4.1 Fertility studies
levels of the infants decreased during nursing. The half-life of phenytoin
in plasma was determined in five cases and varied between 6.6 and          Male fertility
34.0 hours.63
                                                                           Rats
Mirkin (1971) investigated the milk to plasma ratio in two women treated   Shetty (2007) treated male Wistar rats (9-13 weeks old; n=5 per group)
chronically with phenytoin at 300 mg/day. Three measurements were done     intraperitoneally with 3.5, 5.5 or 7.0 mg phenytoin/day (i.e. approximately
during the period of one to 33 days after birth. The plasma concentrations 14-28 mg/kg/day) on five consecutive days. Concurrent negative controls
of one subject were 2.5 to 3.2 µg/ml, of the other 5.4 to 8.4 µg/ml. The   (n=5) were treated intraperitoneally with 0.5 ml water/day. Information on
average concentrations in their milk were 1.5 and 1.7 µg/ml, respectively. general toxicity was not provided. Epididymal sperm morphology,
The women had average milk to plasma ratios of 51% (range 43-59) and       evaluated on days 14 and 35 after the last treatment, showed no
27% (range 15-42), respectively (ranges calculated by the Committee, no    differences in the numbers of normal and abnormal spermatozoa between
consistent increasing or decreasing trend).64                              rats treated with phenytoin and controls.65
2.4 Animal studies                                                         Cohn et al. (1982) administered 20 mg phenytoin/kg bw/day by
In Tables 1 and 2 (Annex A), fertility studies and developmental studies   subcutaneous injection to male Wistar rats (n=11) during three months,
performed in animals are summarized.                                       starting at weaning, postnatal day (PND) 21. The control group (n=10)
                                                                           received saline subcutaneously (volume not reported). Necropsy was
                                                                           performed two days after the last injection. There were no signs of general
                                                                           toxicity (growth was the only endpoint reported). Fertility rate was
                                                                           determined at the end of treatment by caging each male with two
                                                                           untreated females for five days. The males were considered fertile if at
                                                                           least one of the females became pregnant. Fertility was not affected by
                                                                           phenytoin (phenytoin: 5/10 fertile; control: 7/11). Relative reproductive
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<pre>chapter 02 | Phenytoin                                                                                                               Phenytoin | page 34 of 81
organ weights (testis, seminal vesicle, prostate, coagulating gland,            Female fertility
epididymis) and epididymal sperm content and motility were not affected
either.66                                                                       Mice
                                                                                Roberts et al. (1991) treated two strains of female mice (C57BL/6 and A/J;
Cohn et al. (1978) treated male albino rats (age and strain not reported; 5     n=10-13 per group) with phenytoin sodium salt by gastric intubation (0, 40,
or 7 rats per group) subcutaneously with 5, 10 or 20 mg phenytoin/day           65 or 105 mg/kg bw/day) every 48 hours, starting at least one week prior
(corresponding to about 20, 40 and 80 mg/kg bw/day, respectively) on 70         to breeding and continuing throughout pregnancy. Controls (n=10 for
consecutive days. The study included a control group of five rats               C57BL/6, n=12 for A/J) received 5 ml/kg bw/day of the vehicle (water
(treatment not reported). Mean phenytoin concentrations measured in             adjusted with NaOH to pH 11). On gestation day (GD) 10-12 (vaginal plug
tissues from four male rats given 20 mg phenytoin/day subcutaneously for        = GD0), blood was obtained by tail-tip bleeding for determination of dam
12 days were 10.9 µg/ml (serum), 1.9 µg/g (testis), 2.15 µg/g (epididymis),     phenytoin pharmacokinetics. On GD18, dams were sacrificed. Maximal
3.1 µg/g (coagulating gland) and 2.34 µg/g (prostate). Phenytoin                phenytoin serum concentrations were reached 4-8 hr after dosing and
concentration in post-coital uterine fluid was below the limit of detection     approximated 23 (low-dose), 30 (mid-dose) and 33 (high-dose) µg/ml in
(uterine fluid was collected from seven proestrous female rats mated with       C57 mice and 15 (low-dose) and 25 (mid-dose) µg/ml in A/J mice. Serum
males treated with 20 mg phenytoin/day subcutaneously for seven days).          phenytoin remained above the human therapeutic concentration (5 µg/ml)
Phenytoin treated rats showed extensive cutaneous necrosis at the               for most of the interdose interval. Mortality occurred in nonpregnant C57
injection sites (no other information on general toxicity was given). Fertility females at 65 and 105 mg/kg bw/day (1/11 and 5/12, respectively
rate, determined at the end of treatment by caging each male with two           (p<0.05)). It was preceded by weight loss and tremors. Mortality did not
untreated females for five days, was reduced at the highest dose level          occur in nonpregnant A/J dams. The proportion of mated females that
(high dose phenytoin 2/5; control 7/7; p<0.05). Relative reproductive           became pregnant was decreased at the highest dose in C57 mice
organ weights (testis, seminal vesicle, prostate, coagulating gland,            (phenytoin 2/12; control 8/10, p<0.01). It was decreased dose-
epididymis), epididymal sperm content and motility, Leydig cell count and       dependently in A/J mice (phenytoin 9/12, 5/11 and 0/13 at 40, 60 and
blood testosterone concentration were not affected by exposure to               105 mg/kg bw/day, respectively; control 10/12), but the decrease was only
phenytoin.67                                                                    statistically significant at the highest dose (p<0.01). The proportion of
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<pre>chapter 02 | Phenytoin                                                                                                            Phenytoin | page 35 of 81
females that mated, total number of implantations per litter and number of dead in one out of six litters. Additionally, all foetuses of the one dam
viable implantations per litter were not affected by exposure to           examined after 1500 mg/kg phenytoin per day were resorbed. A dose-
phenytoin.68                                                               dependent intrauterine growth retardation was observed, which was
                                                                           characterized by decreases in foetal weight, crown-rump length and
2.4.2 Developmental toxicity studies                                       ossification of the appendicular and axial skeleton (compared to controls,
                                                                           all p<0.05). An increased percentage of malformed foetuses per litter was
Structural defects                                                         observed at 750 and 1,125 mg/kg/day doses (compared to controls,
                                                                           p<0.05). Visceral malformations included cardiovascular malformations
Gavage                                                                     (mainly absent aortic arches), urogenital anomalies (mainly
                                                                           hydronephrosis and ectopic kidneys) and craniofacial malformations
Rats                                                                       (mainly highly arched palates often associated with a thin, tapered snout).
Rowland et al. (1990) daily administered phenytoin (2,2-diphenylhydantoin  Skeletal malformations included hemivertebrae and fused vertebrae in the
sodium salt) to pregnant Sprague-Dawley rats (n=4-9 per group) by          cervical and thoracic regions.69
gavage on GD8 to GD17. Doses of 0, 150, 375, 750, 1125, and 1500 mg/
kg bw/day phenytoin were administered. Reproductive outcomes were          Zengel et al. (1989) evaluated the effect of prenatal phenytoin on the
determined at GD20.                                                        postnatal growth and craniofacial morphology in mature rats. Pregnant
After the oral dosing, a dose-dependent increase of maternal toxicity was  females were treated with 1,000 mg/kg bw phenytoin (suspended in 1%
observed, which was characterized by impaired motor function, decreased    solution of carboxymethylcellulose) by gavage on days 9, 11 and 13 of
maternal weight gain (p<0.05), hepatic necrosis and gastritis. Maternal    gestation. Controls received an equivalent volume of the vehicle on the
deaths occurred between GD10 and GD17 in the groups treated with           same days. Group size and maternal toxicity were not described. After
1,125 mg/kg/day (2/8 dams dead) and 1,500 mg/kg/day (3/4 dams dead).       delivery, pup weight was recorded frequently till postnatal day (PND) 135,
The reproductive outcomes of the remaining dams in these dose groups       when pups were sacrificed and skeletons were prepared for analysis.
were affected. An increase in embryonic loss occurred at 1125 mg/kg/day:   Average litter size after delivery was comparable, but a higher pup
all foetuses were resorbed in two out of six litters; 11/14 foetuses were  mortality was observed in phenytoin-treated animals (94% compared to
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<pre>chapter 02 | Phenytoin                                                                                                          Phenytoin | page 36 of 81
1% in controls). At the time of weaning on PND25 all viable pups from the    However, the maternal mortality or toxicity was not specified. Furthermore,
phenytoin-treated dams which were left, were used for the examinations.      dam group size was not reported.
Non-viable pups were not further examined. Six male and six female pups      Rats exposed in utero to 1,000 mg/kg bw/d on GD9-13 exhibited foetal
of the control group were randomly selected from five control litters. After onset growth retardation, abnormalities of the craniofacial region and axial
weaning, body weight accumulation was reduced in the offspring of            skeleton. In addition, the exposed offspring had lower body weights than
treated females (compared to controls, p<0.01, 0.02 or 0.05, at several      controls at all foetal ages examined (GD14.5-18) and at birth (all p<0.05).
time points from PND 36 on). Male pups were more affected than female        They also had a shortened snout and high-arched, irregular palate, and
pups. All pups from treated females showed less protrusion of the eyes,      delays in skeletal maturation, demonstrated by reduced bone length and
absent or rudimentary lacrimal bones and presence of nasolacrimal            ossified bone length at birth (both p<0.05). No consistent information was
canals. Examination of the skeletons revealed reduced body length            provided on other dosage regimens, but retarded palatal growth was also
(compared to controls, p<0.05) and changes in craniofacial morphology in     observed at a 15% incidence at single day administration of 700-1,000
both male and female pups from phenytoin-treated females. The                mg/kg bw.71
craniofacial changes included reduced cranial length (p<0.005),
bizygomatic width (p<0.005), facial height (p<0.005) and maxtransfrontal     Kim et al. (2012) treated pregnant Sprague-Dawley rats with phenytoin by
width (p<0.01).70                                                            gavage at doses of 0, 50, 150, or 300 mg/kg bw/day (11 animals per dose
                                                                             group) from GD6 through GD15. They investigated the dose-response
Lorente et al. (1981) treated pregnant CD rats with phenytoin by gavage      effects of phenytoin on pregnant dams and embryo-foetal development as
at doses of 700, 800 or 1,000 mg/kg bw/d, either on single or multiple       well as the relationship between maternal and developmental toxicity. At
days of gestation in the periods GD9-11, GD9-13, GD10-12, GD10-14,           300 mg/kg bw/day, various signs of maternal toxicity were observed:
GD11-13, GD12-14 or GD13-15. With these high-dosage regimens, the            increased clinical changes such as ataxia and seizure, suppressed body
authors aimed to produce the greatest number of anomalies with the           weight and body weight gain (p<0.01), decreased food intake (p<0.01),
lowest level of maternal mortality. The multiple-dose regimen of 1,000 mg/   decreased absolute weights of lung, spleen, heart, and brain and
kg bw/d on GD9-13 was chosen, because it produced a relatively low           increased relative weights of adrenal glands, kidneys, brain, ovary and
maternal mortality, but the longest exposure of the foetus to phenytoin.     liver as compared to the control group (p<0.01 or p<0.05, depending on
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<pre>chapter 02 | Phenytoin                                                                                                           Phenytoin | page 37 of 81
the organ). At 150 mg/kg bw/day, maternal toxicity signs similar to those at cleft lips, haematomas, hydroencephaly and exencephaly (compared to
300 mg/kg were present (p<0.01), though less strongly: suppressed body       controls, p-values ranged from <0.001 to <0.0001). These lesions were
weight and body weight gain, decreased food intake, a decreased              however, not specified per time point and dose level.73
absolute weight of the heart and increased relative weights of adrenal
glands and brain. No treatment-related maternal effects were observed at     Fritz et al. (1976) treated mated (Tif/MAG) mice (n=30/group) with 0, 15,
50 mg/kg bw/day.                                                             50, 100 or 170 mg phenytoin/kg bw/d during GD6-15 by gavage. Offspring
At 300 mg/kg bw/day, developmental toxicity, including decreased foetal      was subjected to visceral (one third) and skeletal examination (two thirds).
and placental weights (p<0.01), an increased incidence of morphological      Ten dams in the high-dose group died. In the lower dose groups, there
alterations (p<0.01) and a delay in foetal ossification occurred (p<0.01 or  was no maternal mortality. At the next higher dose of 100 mg/kg food
p<0.05, depending on the parameter), as compared to the controls.            intake was diminished. The reactions of the dams in the lower dose
Developmental toxicity was less severe at 150 mg/kg bw/day than at 300       groups (15 and 50 mg/kg) did not differ from those of the controls. No
mg/kg bw/day. It was restricted to a decreased placental weight (p<0.01)     further information on maternal toxicity was given. Early embryonic death
and an increased incidence of visceral and skeletal alterations (p<0.01).    occurred at 100 and 170 mg/kg bw/d, and mean foetal weight was
No treatment-related developmental effects were observed at 50 mg/kg         reduced in these groups, as compared to the controls (p<0.01). There was
bw/day.72                                                                    a dose-related increase in cleft palate at 15, 50, 100 and 170 mg/kg bw/d
                                                                             (0.3%, 2%, 5.2% and 9.3%, respectively, versus 0.13% in historical control
Mice                                                                         data from 500 mice), which was statistically significant from 50 mg/kg
Eluma et al. (1984) administered phenytoin to pregnant CD 1 mice at          bw/d onwards (compared to controls, p<0.01). Skeletal examination
levels of 0, 50, 75 and 125 mg/kg bw/d by gavage during GD8-10,              showed incomplete ossification of the fore-limbs at 170 mg/kg bw/d
GD11-13, GD14-16 or GD8-16 (2 mice/group/time point; six mice per            (p<0.01), but no malformations.74
control group). Information on maternal toxicity was not presented. Foetal
weight showed a window-dependent and dose-related decrease in all            Roberts et al. (1991) treated two strains of female mice (C57BL/6 and A/J;
treatment groups (p-values not mentioned). In treated offspring, a high      n=10-13/group) with phenytoin sodium salt by gastric intubation (0, 40, 65
incidence of cleft palate was noted, and a lower incidence of foetal death,  or 105 mg/kg bw/day) every 48 hours, starting at least 1 week prior to
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<pre>chapter 02 | Phenytoin                                                                                                              Phenytoin | page 38 of 81
breeding and continuing throughout pregnancy. Controls (n=10 for C57,           calcium deposit (inside the apex of the left ventricle) was increased (at 40
n=12 for A/J) received 5 ml/kg bw/day of the vehicle (water adjusted with       mg/kg) in C57 mice (all p<0.05).68
NaOH to pH 11). On GD10-12 (vaginal plug = GD0), blood was obtained
by tail-tip bleeding for determination of dam phenytoin pharmacokinetics.       Cats
On GD18, dams were sacrificed. Gestational weight gain, gravid uterus           Khera (1979) treated pregnant cats (n=13-14 per group) with 0, 1 or 2 mg
weight and foetal weight were determined. Foetuses were examined for            phenytoin sodium salt/kg bw/d by gavage during GD10-22, and
visceral and skeletal abnormalities. These endpoints could not be               necropsied them on GD 43. Foetuses were examined for external, visceral
examined in A/J mice at 105 mg/kg because there were no pregnant                and skeletal malformations.
females at this dose. Maximal phenytoin serum concentrations were               Maternal body weights were decreased at 2 mg/kg bw/d on GD20 and
reached 4-8 hr after dosing and approximated 23 (low-dose), 30                  GD30 (compared to controls, p<0.05), but normal at GD40 and GD43.
(mid-dose) and 33 (high-dose) µg/ml in C57 mice and 15 (low-dose) and           Maternal body weights were normal at 1 mg/kg bw/d at all time points. The
25 (mid-dose) µg/ml in A/J mice. Serum phenytoin remained above the             incidences of abortion, non-pregnancy, live or dead foetuses and mean
human therapeutic concentration (5 µg/ml) for most of the interdose             foetal weights were within control range. The number of resorptions was
interval. Mortality occurred in nonpregnant C57 females at 65 and 105           higher in the 2 mg/kg bw/d group than in controls (p<0.05). There were no
mg/kg bw/day (1/11 and 5/12, respectively) and was preceded by weight           treatment-related anomalies in live foetuses. A high incidence of
loss and tremors. Gestational weight gain and gravid uterus weight were         malformations however, was noted in test foetuses from four aborting cats
dose-dependently decreased in C57 mice (compared to controls,                   (on GD31-37): one control cat, two cats given 1 mg/kg bw/d and one cat
statistically significant by a linear trend analysis, p<0.05). Postimplantation given 2 mg/kg bw/d. None of the seven foetuses from the control cat were
loss was decreased in A/J mice given 65 mg/kg bw/day (p<0.05). Foetal           anomalous, whereas all eleven foetuses from the two cats given 1 mg/kg
weight was only lower at 65 mg/kg in C57 (p<0.05). There was decreased          bw/d had cleft palate and open eyelids and four out of the ten foetuses
ossification of the sternebrae (in C57 at 65 mg/kg, p<0.05) and of the          from the cat given 2 mg/kg bw/d had umbilical hernia and one had open
thoracic centra, metacarpals and metatarsals (in A/J at 65 mg/kg, p<0.05).      eyelids.75
The frequencies of hydroencephaly (at 65 mg/kg) and open eyelid (at 40
and 65 mg/kg) were increased in A/J mice, and the frequency of cardiac
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<pre>chapter 02 | Phenytoin                                                                                                          Phenytoin | page 39 of 81
Water intake                                                                 Feed
Mice                                                                         Mice
Finnell et al. (1989) exposed three strains of virgin female mice (SWV,      Hansen and Billings (1986) treated pregnant A/J mice with phenytoin via
LM/Bc and C57BL/6J) to phenytoin (0, 10, 20, 40, or 60 mg/kg bw) orally      the diet prior to and throughout gestation (daily dose of 0, 60 or 75 mg/kg)
via the drinking water for a 15-day period (before mating) and throughout    to investigate the effects of chronic exposure to phenytoin. On GD18 or
gestation until GD18. Phenytoin was administered before mating in order      -19, mice were sacrificed and foetuses were examined. Blood samples
to reach a steady state concentration of phenytoin, which was within the     were collected from phenytoin-treated dams and their phenytoin
desired therapeutic range for a mouse (within 2.5 and 12.5 μg/ml plasma).    concentrations were determined. These concentrations were 9.2±0.9
No information on maternal toxicity was reported. A dose-dependent           µg/ml of plasma at 60 mg/kg body weight and 13.0±0.9 µg/ml at 75 mg/kg.
decrease in foetal weight was observed in all strains (compared to           Maternal toxicity, indicated by food consumption, weight gain rate,
controls, p<0.05). Additionally, the incidence of offspring with one or more sedation and ataxia was not observed after phenytoin administration in the
congenital abnormality was enhanced with increasing doses of phenytoin       diet (data not shown). A decrease in foetal weight was observed at both
in all mice strains (p<0.05). These included both skeletal defects (mainly a doses (compared to controls, p<0.05) and a decrease in the number of
pattern of multiple malformations and ossification delays in supraoccipital  implantation sites in the highest dose group (p<0.05). No increase in the
bones, sternebrae, distal phalanges and midfacial bones) and soft tissue     incidence of clefts was found.77
defects (mainly dilated or immaturely developed cerebral ventricles and
renal defects, digital, cardiac and ocular anomalies). A correlation was     Intraperitoneal injection
observed between the risk of offspring with abnormalities and plasma
phenytoin (p<0.05).76                                                        Rats
                                                                             Soysal (2011) treated female Wistar albino rats (n=7) on GD8-10 with 25
                                                                             mg/kg phenytoin diluted with serum physiologic intraperitoneally. A control
                                                                             group (n=6) was included. On GD20, foetuses were isolated by
                                                                             Caesarean section. Maternal toxicity was not reported upon. Forty
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<pre>chapter 02 | Phenytoin                                                                                                           Phenytoin | page 40 of 81
foetuses of the control group and 42 foetuses of the phenytoin-treated         dihydrotestosterone in male offspring were not affected at days 8, 28 or
group were examined for bone and cartilage defects. Mean length (2.75±         120 PP. Levels of the hormone androstenedione in male offspring
0.29 cm) and weight (3.04±0.42 g) of foetuses from drug-treated animals        exposed in utero to 50 mg/kg were increased at day 8 PP (p<0.02), and
were different from the control group (length 3.21±0.27 cm and weight          decreased at day 28 PP (p<0.02). Estrous cyclicity (vaginal smears from
3.51±0.35 g; p<0.001). Ossification of the skull bones in drug-treated         about 13-week old offspring) and weights of the uterus and ovaries (at
foetuses was deteriorated (increased costal separation in 10/42 foetuses       about 16 weeks PP) were examined in female offspring. These endpoints
of drug-treated mothers) and shape malformations in the ribs were              were not affected by prenatal exposure to phenytoin. 79
observed.78
                                                                               Mice
Shapiro et al. (1987) treated female Sprague-Dawley rats with 10, 50 or        Hansen and Hodes (1983) administered phenytoin to groups of 25
100 mg phenytoin sodium salt/kg body weight/day intraperitoneally from         pregnant ICR mice at doses of 0, 50, 75 or 100 mg/kg bw/d by
GD17 through day 7 post partum (PP). Vehicle controls received 0.93 ml         intraperitoneal injection on GD10-12. The highest dose was lethal to the
water (pH 11.6)/kg bw/day. On the basis of previous studies 100 mg/kg bw       dams and omitted from the study. Maternal toxicity (measures not
was assumed to be within the human therapeutic range. Information on           specified) was not observed at doses of 50 and 75 mg/kg bw/d. Mean
general toxicity in the dams was not provided. At 100 mg/kg about half of      foetal weight and crown rump length showed a dose-related decrease in
the dams lost all their foetuses, the other half delivered two days later than both test groups (compared to controls, p<0.01 or p<0.05), while
the other groups and had normal litter sizes. Offspring of dams treated        transumbilical distance was decreased in the 75 mg/kg bw/d group only
with 50 or 100 mg/kg had decreased body weights from birth throughout          (p<0.01). The incidence of malformed foetuses was increased at 75 mg/kg
their life (compared to controls, p<0.05). Male offspring of the 10 and 50     bw/d (p<0.05), with orofacial anomalies most frequently observed
mg/kg groups showed decreased relative testis weights at day 8 PP              (p<0.01). Other malformations included ectopic kidneys, cryptorchydism
(p<0.002 and p<0.02, respectively), but not at days 28 or 120 PP (no data      and cardiac defects, but no data were presented. Skeletal defects were
for the 100 mg/kg group). At day 120 PP, relative seminal weight was           not found in any group. A dose of 75 mg/kg bw/d was also administered to
decreased in the 50 and 100 mg/kg groups (p<0.02 and p<0.001,                  groups of 19 or 20 pregnant A/J, C57BL/6J, B6AF1, AB6F1, (B6A)F2 and
respectively). Serum levels of the hormones testosterone and                   C3H/He mice on GD10-12. Fifteen or 20 pregnant animals of the same
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<pre>chapter 02 | Phenytoin                                                                                                         Phenytoin | page 41 of 81
strain received vehicle and served as controls. A higher number of           intravenous injection on GD8 to GD17. Doses of 0, 25, 50, 75, and 100
resorptions was observed in two strains, a higher number of malformed        mg/kg bw/day were administered. Reproductive outcomes were
foetuses in three strains, a higher number of orofacial anomalies in two     determined at GD20. After the intravenous dosing, a dose-dependent
strains and a lower foetal weight in three strains treated with phenytoin as increase in maternal toxicity was observed, which was characterized by
compared to control animals (p<0.01 or p<0.05).80                            mild to severe imbalance and ataxia in the 50 and 75 mg/kg groups. Due
                                                                             to excessive ataxia in the 100 mg/kg group, this dose was discontinued.
Hansen and Billings (1986) treated pregnant A/J mice with phenytoin by       No decreases in maternal weight gain were evident after intravenous
intraperitoneal injection on GD10 (0, 60 or 75 mg/kg) to investigate the     dosing. Decreases in foetal weights and crown-rump lengths and
effects of acute exposure to phenytoin. The plasma phenytoin levels of the   increases in foetal malformations (mainly craniofacial malformations, i.e.
phenytoin-treated dams were determined on GD12. These levels were            thin, tapered snouts and arched palates) occurred at 75 mg/kg phenytoin
5.8±1.2 µg/ml of plasma at 60 mg/kg body weight and 17.0±1.0 µg/ml at        (compared to controls, p<0.05).
75 mg/kg. On day 18 or 19 of gestation, mice were sacrificed and foetuses    Pharmacokinetic sampling on GD8-9 and GD16-17 revealed an increase
were examined. Phenytoin administered by intraperitoneal injection           in plasma phenytoin exposure between the beginning and the end of the
resulted in sedation and ataxia for approximately 24 hours in the high-      treatment period.69
dose dams. A dose-related increase in resorptions was observed
(compared to controls, p<0.05) and nearly all of the surviving foetuses had  Functional and cognitive effects
a morphological abnormality, mainly cleft lip and palate (p<0.05). No effect
was observed on foetal weight.77                                             Gavage
Intravenous injection                                                        Rats
                                                                             Mowery et al. (2008) dosed female Sprague-Dawley rats twice daily with 0
Rats                                                                         or 50 mg phenytoin/kg bw/d by gavage from ten days before mating,
Rowland et al. (1990) administered phenytoin (Dilantin, phenytoin sodium     throughout pregnancy and the three week preweaning period. Maternal
injection) to pregnant Sprague-Dawley rats (n= 4-9 per group) by             plasma levels on the last day of dosing approximated the low level of
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<pre>chapter 02 | Phenytoin                                                                                                              Phenytoin | page 42 of 81
human therapeutic concentrations (10-20 µg/ml). Information on maternal        offspring demonstrated impaired reference memory based spatial
toxicity was not provided. Behavioural testing was conducted with 80-90        learning, cued (visible) platform learning, spatial discrimination and
days old female offspring (test group: n=31 from 11 litters; controls: n=22    working memory-based learning (all p<0.01).82
from 10 litters). Female rats developmentally exposed to phenytoin
showed increased performance in simple associative learning tasks              McCartney et al. (1999) dosed pregnant Sprague-Dawley rats (≥20 dams
(appetitive-to-aversive transfer paradigm; compared to controls, p<0.05),      per group) with 0, 50, 100 or 150 mg phenytoin sodium salt/kg bw/d by
but displayed impaired performance in a higher-order learning and              gavage during GD7-18. Examinations were conducted in all pups
memory task (avoidance conditioning, p<0.05).81                                (preweaning) or in 1 pup/sex/litter (postweaning). Various developmental
                                                                               and behavioural indices were evaluated. Maternal weight gain showed a
Schilling et al. (1999) dosed pregnant Sprague-Dawley rats (10 controls,       dose related reduction in all treatment groups (compared to controls,
15 treated dams) with 0 or 200 mg phenytoin/kg bw/d by gavage during           p<0.05), and other signs of maternal toxicity, i.e. increased incidences of
GD7-18. They tested the effects on learning and memory, as well as on          chromodacryorrhea, lacrimation and circling, were noted in the 100 and
circling behaviour in water. Maternal body weight was decreased in the         150 mg/kg bw groups (data not reported). Accelerations in developmental
treatment group during GD14-18 (compared to controls, p<0.05).                 landmarks and preweaning behaviour (eye opening, incisor eruption,
Offspring mortality was increased in the treatment group during the first      negative geotaxis and olfactory orientation) and delays in air righting were
week(p<0.01). Per litter, two male offspring were tested, one exhibiting       noted among all offspring treatment groups (p<0.05). Locomotor activity
circling in a straight water channel and one in a circling tank. Circling in a was increased in high-dose pups (at PND21) and adults (at PND62)
water channel occurred in 53% of the exposed offspring. Circling was,          (p<0.05). Dose-related performance deficits were noted in a water maze
however, never seen in the control group. Litter characteristics showed no     assay (learning/memory impairments, p<0.01) and in auditory startle
differences between the groups. Preweaning body weights were not               responses (p<0.05 in at least one dose group). For a number of these
affected. Postweaning body weights were decreased in the treatment             endpoints, male and female rats showed different sensitivity.
group (p<0.05 or p<0.01).                                                      Offspring brain weights also showed sex differences in sensitivity, that
Noncircling phenytoin-exposed offspring demonstrated impaired reference        depended on age. Hind brain weights were reduced in male pups at 150
memory-based spatial learning in the Morris water maze (p<0.05). Circling
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<pre>chapter 02 | Phenytoin                                                                                                                 Phenytoin | page 43 of 81
mg/kg bw/d (p<0.05). Forebrain and whole brain weights were reduced in       behaviour and tested at approximately 50 days of age. Phenytoin offspring
adult females at 100 and 150 mg/kg bw/d (p<0.05).83                          committed more errors and had longer latencies to find the goal than
                                                                             controls in the Cincinnati (water) Maze (compared to controls; circling
Tsutsumi et al. (1998) dosed pregnant Sprague-Dawley rats (7-10 dams         animals: p<0.01; noncircling animals: p<0.05). The effects in circling
per group) by gavage with 0, 50 or 100 mg phenytoin/kg bw/d by gavage        animals were larger than those in noncircling animals.85
during GD7-18, and subjected male offspring (generally 10-15 males/
group) to a reflex test and several learning/memory tests. No information    Pizzi et al. (1992) dosed pregnant Sprague-Dawley rats (10-11 dams per
on maternal toxicity was provided. The completion of the negative            group) with 0, 100 or 200 mg phenytoin sodium salt/kg bw/d by gavage
geotaxis (reflex) test was delayed in both treatment groups (compared to     during GD9-18.
controls, p<0.001). No effects of phenytoin were detected in a figure-eight- Phenytoin administration resulted in a dose-related decrease in maternal
maze, a Biel water maze, or a Morris maze test. In a radial maze test, the   weight gain (compared to controls, both doses p<0.001). Maternal plasma
total number of choices was higher (p<0.05), whereas the number of           levels in the low- and high-dose groups were 11.5 and 26.2 mga
correct choices was lower in the high-dose group (p<0.05). The               phenytoin/ml. Offspring had lower birth weights and body weights at
percentage of correct choices in the high-dose group was also lower in a     PND30 (high dose group males and females: p<0.001; low dose group
delayed nonmatching-to-sample test (T-shaped maze, p<0.05). Offspring        males p<0.05). This was accompanied with increased mortality (41% and
whole brain weights were decreased in the high dose group in week 6          61% in the low- and high-dose group, respectively). Phenytoin-exposed
(p<0.05), whereas their body weights were unaffected. The brain weights      offspring frequently showed chromodacryorrhea. Pups exposed in utero to
had returned to normal at 16 weeks of age.84                                 100 mg/kg bw/d showed an increase in pivoting locomotor activity on
                                                                             PND7 and 9 (p<0.005). Due to mortality, the 200 mg/kg bw/d group was
Vorhees et al. (1995) dosed pregnant Sprague-Dawley rats (5-6 dams per       not examined for this activity. Phenytoin-exposed offspring developed an
group) with 0 or 100 mg phenytoin sodium salt/kg bw/d in corn oil by         abnormal spontaneous circling behaviour (12 and 33% in the low- and
gavage during GD7-18. Maternal weight gain, gestation length, pups per       high-dose group, respectively, compared to 0% of the controls). As adults,
litter and sex ratio within litters were not affected. Phenytoin offspring
(number/group not indicated) were subdivided according to circling           a
                                                                               The Committee assumes that µg rather than mg was meant.
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<pre>chapter 02 | Phenytoin                                                                                                          Phenytoin | page 44 of 81
the animals exposed to 200 mg/kg bw/d showed increases in locomotor         weights were decreased in the high-dose group during gestation
activity measures (at PND45: p<0.05; at PND66: p<0.05).86                   (compared to controls; GD18 (p<0.01) and GD20 (p<0.05)). Litter
                                                                            numbers were not affected by prenatal exposure to phenytoin . Offspring
Weisenburger et al. (1990) dosed pregnant Sprague-Dawley rats (10-13        mortality was increased in the high-dose group during PND1-21 (p<0.01).
litters/group remained) by gavage with 0, 100 or 200 mg phenytoin/kg        Offspring of both sexes (number/group not indicated) was tested prior to
bw/d by gavage during GD7-18. Where possible, six pups/sex/litter were      weaning (for activity only) and afterwards. The highest dose of phenytoin
retained for testing. Maternal serum concentrations on GD18 were 15.1       produced increased activity (in various tests of activity, p<0.01), delayed
and 20.9 µg/ml for low- and high-dose, respectively. Maternal weight gain   dynamic righting development (p<0.01), impaired Biel multiple-T water
was reduced in both treatment groups (compared to controls, p<0.05).        maze learning (p<0.01), Y-maze avoidance learning (p<0.05), and
Pup mortality was increased at 200 mg/kg bw/d at birth (p<0.01), PND7       inhibited tactile startle responses (p<0.05). The two lower doses of
(p<0.01) and PND28 (p<0.05). Preweaning and postweaning offspring           phenytoin generally showed a dose-effect relationship on most measures.
body weights were reduced at 200 mg/kg bw/d (p<0.05). Exposed               Phenytoin-exposed offspring showed a dose-related increase in circling
offspring showed dose-related increases in circling behaviour (both doses:  behaviour (p<0.05 or p<0.01). Offspring showed no effects on postnatal
p<0.01), preweaning locomotor activity (both doses: p<0.05), errors in a    growth, total brain weight, or brain protein content as adults (at 79-84 days
complex water maze (p<0.01) and impaired performance in a radial-arm        of age).88
maze (both circlers and noncirclers at each dose p<0.01).87
                                                                            Ruiz et al. (1987) dosed Sprague-Dawley rats with 0 or 50 mg phenytoin/
Vorhees (1987) dosed pregnant Sprague-Dawley rats (13-20 litters/group)     kg bw/d by gavage from 7 days before fertilization, throughout pregnancy.
by gavage with 0, 100, 150 or 200 mg phenytoin/kg bw/d by gavage            Pups were also given the drug by gavage, but the dosing regimen was not
during GD7-18. These doses resulted in maternal plasma levels on GD18       reported. Information on maternal toxicity was not given either. Neuronal
(4h after dosing) of about 10, 20 and 24 µg/ml, in the low-, mid- and high- structure in the somatosensory cortex at 30 days of postnatal
dose group, respectively (with little decline up to 24h). The adult/        development was investigated in six offspring/group. The cortical layers III
embryonic plasma ratio in five individual rats of the mid- and high-dose    and IV in phenytoin-treated rats and controls showed no major
group at 24h post-dosing on GD18 was between 1.3 and 2.4. Maternal          differences. However, the total cell density in layer V was higher in treated
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<pre>chapter 02 | Phenytoin                                                                                                              Phenytoin | page 45 of 81
animals (compared to controls, p<0.0001). Numbers and lengths of apical         dynamic righting reflex (no statistics reported), a decreased ability of
and basilar dendrites were decreased (p<0.05 to p<0.0001). The degree           offspring to stay on a rotating rod (p<0.05), and a decrease ability to walk
of neuronal maturation at the level of collateral apical dendrites of           along elevated parallel rods (p<0.01). There were no changes in
pyramidal cells was diminished in the surface layers of the cortex, while       development of physical landmarks, or in the development of crawling and
poor development of the basilar dendrites was also seen in the deeper           walking activities at 9-21 days of age, and no changes were seen in a
layers of the sensory cortex of the treated animals. The pattern of             head-dipping test or in a conditioned avoidance test (shuttle box) at 26-34
phosphorylation of cytoskeletal proteins was changed in the treated             days of age. There was a decrease in absolute brain weight of the treated
animals.89                                                                      group at age three days (p<0.05 or <0.001), which in males remained
                                                                                lower than the controls even at 90 days (p<0.001). There was no
Elmazar and Sullivan (1981) dosed pregnant Wistar rats (10 (first study)-       difference in cerebellar DNA content. 90
20 (repeat study) litters/group) with 0 or 100 mg phenytoin/kg bw/d by
gastric intubation during GD7-19. Previously, 100 mg/kg had been shown          Vorhees (1983) administered phenytoin or vehicle to pregnant Sprague-
to produce a steady-state situation by GD19, with a blood level of 6.7±1.8      Dawley rats by gavage and investigated the effects of different dose
µg/ml, 24 hours after dosing, being within the human therapeutic range.         regimens in three experiments. Structural effects and postnatal functioning
The maternal body weight decreased up to day 10 and then increased to           were investigated on GD20 or postnatally. The first experiment served to
about 300 g at day 19. Due to paired feeding, the body weights of the           determine the highest dose for assessing postnatal functional
control dams followed the same pattern. After parturition, the offspring was    teratogenesis in experiments 2 and 3. In this dose range-finding study with
culled to six-eight/litter and reared by fostering or cross fostering. Survival five or six rats per group 200 mg/kg bw/day was chosen as the highest
and body weights of the pups from treated mothers were lower than in            dose to be used in the other experiments. This choice was based on
control pups in two experiments at two days of age (p<0.05), in one of the      maternal toxicity (reduced maternal weight; compared to controls, p<0.01)
experiments at 21 days of age (p<0.01) and at 90 days of age (p<0.05),          and the fraction of resorbed or dead foetuses (not statistically different
as compared to controls. Both of these effects could be reduced by cross        from controls).
fostering. A number of neurological effects were seen in the phenytoin          In the second experiment, doses of 0, 5, 50 or 200 mg/kg bw/day were
group; there was a delay of up to fifteen days in the development of the        administered on GD7-18 (group size not reported). Maternal weight was
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<pre>chapter 02 | Phenytoin                                                                                                            Phenytoin | page 46 of 81
decreased at 200 mg/kg bw/day on GD14 and GD18 (p<0.05), and during           Offspring mortality was increased during the preweaning period after
lactation (p<0.01). Length of gestation, external malformations, number of    treatment at GD7-10 (p<0.001) and GD15-18 (p<0.01). It was also
offspring delivered and sex ratio within litters were not affected. Offspring increased postweaning after treatment at GD11-14 (p<0.01). No treatment
mortality was increased at 50 and 200 mg/kg bw/day on PND0 (both              effects were found on incisor eruption, eye opening or vaginal patency
p<0.0001) and at 200 mg/kg bw/day on PND 21 (p<0.001). The mortality          development. In the preweaning period no treatment effects were found
had returned to normal on PND22-70. Before weaning (PND1-21), no              on righting, negative geotaxis, olfactory orientation, figure-8 activity or
reduction in offspring body weight occurred in any dose group compared        neonatal T-maze behaviour. Phenytoin increased preweaning pivoting
to controls (data not shown). After weaning (PND22-70), offspring body        locomotion and delayed swimming development in the groups exposed at
weight was reduced: the 200 mg/kg group was 10.8% lighter than the            GD11-14 or GD15-18 (p<0.05 or <001), but it did not affect startle. No
controls on PND42 (p<0.001) and 7.2% lighter on PND70 (p<0.05). No            treatment effects were observed on postweaning M-maze behaviour or
treatment effects were found on lower incisor eruption, eye opening or        spontaneous alternation. Phenytoin also increased postweaning figure 8
vaginal patency development. In the preweaning period no treatment            ambulation (p<0.01) and water maze errors (p<0.001) and impaired
effects were found on negative geotaxis, olfactory orientation, figure-8      passive avoidance retention in the GD11-14 exposure group (p<0.05).91
activity or neonatal T-maze behaviour. Treatment effects were found in
tests of righting (data not shown), pivoting and startle (200 mg/kg;          Mice, newborn
compared to controls, both p<0.001), as well as swimming (200 mg/kg,          The neonatal period in mice corresponds to the period of development of
at various ages, p<0.05). No treatment effects were observed on               the central nervous system in the third trimester of human pregnancy.
postweaning M-maze behaviour, passive avoidance or spontaneous                Therefore, the following experiments with neonatal mice are relevant for
alternation. Phenytoin affected postweaning figure-8 activity and Biel        assessing the effects of phenytoin on the developing central nervous
water maze learning (200 mg/kg bw/day, p<0.05 to p<0001).                     system.
In the third experiment, doses of 0 or 200 mg/kg bw/ day were given on
GD7-10, 11-14 or 15-18 (group size not reported). Maternal weight was         Ogura et al. (2002) dosed newborn C57BL/6 mice (13-15 males/ group)
not affected. Length of gestation, external malformations, number of          with 0 or 35 mg phenytoin/kg bw/d by gavage during PND5-14. Plasma
offspring delivered and sex ratio within litters were not affected either.    level of phenytoin was 20 ± 2.8 µg/ml, 3h after the last dose. Brain
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<pre>chapter 02 | Phenytoin                                                                                                            Phenytoin | page 47 of 81
concentration of phenytoin was 1.6 times higher (31.9±10.3 µg/ml). Some      Total brain weight, cerebral weight and cerebellar weight were reduced in
treated pups showed acute behavioural detoriation, including anorexia,       treated mice (p<0.01). Phenytoin induced neurotoxic damage in the
hyperactivity and motor coordination deficits. Mortality (38%) and weight    developing cerebellum; it induced cell death of external granule cells and
loss was noted in the treated pups, but at 56 days of age the body weights   inhibited migration of granule cells in the cerebella, and affected Purkinje
of treated mice had returned to control values. Brainstem weight, cerebral   cell differentiation. 93
weight, cerebellar weight and total brain weight were reduced in treated
56 days old mice (p<0.01). Histopathological examination showed that         Hatta et al.(1999) administered phenytoin to newborn Jcl:ICR mice
phenytoin treatment interferes with the development of granule cells in the  (number per group not indicated) at levels of 0, 10, 17.5, 25 or 35 mg/kg
hippocampus and the cerebellum, and with the dendritic development of        bw/d by gavage on PND2-4. Mortality rate in the high-dose group was 8%
Purkinje cells. Treated mice were impaired in the acquisition of a hidden    in either sex. Pup body weights (on PND5-PND21) did not differ from
platform task in a water maze test (compared to controls, p<0.001), and      those in controls. Mice treated with 25 or 35 mg/kg bw/d showed
committed more errors during the learning process in a radial arm maze       decreased locomotor abilities and righting reflex on PND5 (compared to
than controls (p<0.01). 92                                                   controls, p<0.05 or <0.01). Total brain weight, cerebral weight and
                                                                             cerebellar weight were decreased in pups treated with 25 or 35 mg/kg
Ohmori et al. (1999) administered phenytoin (0 or 35 mg/kg bw/d) to          bw/d (p<0.05 or <0.01).94
newborn Jcl:ICR mice (13-16/sex/group) by gavage during PND2-4.
Plasma level of phenytoin on the third day of administration was 17.7        Monkeys
µg/ml; in the brain, the level was higher (31.4 µg/g). Mortality was >30% in Phillips and Lockard (1993) dosed four adult female monkeys (Macaca
males and females of the treatment group versus none in controls. Weight     fascicularis) with phenytoin via stomach catheter from one month before
loss, anorexia, motor hypoactivity and incoordination was noted in treated   mating throughout gestation. The animals were dosed twice daily at levels
pups at PND4 (data not shown). Their body weight recovered to normal at      providing plasma concentrations between 4-12 µg/ml phenytoin (the initial
PND56. Motor performance of the treated mice in a rotating rod was           dose was 20 mg/kg bw). The infants were investigated for
impaired (compared to controls, p<0.05). Their spontaneous locomotor         hyperexcitability. Control groups consisted of monkeys treated with
activity, detected by movements in a box, was impaired as well (p<0.01).     stiripentol (n=5), or phenytoin plus stiripentol (n=4), because stiripentol
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<pre>chapter 02 | Phenytoin                                                                                                               Phenytoin | page 48 of 81
has been shown to reduce the incidence of phenytoin-induced congenital           2.4.3 Lactation
malformations in mice. Information on maternal toxicity was not given.           No relevant animal studies on effects of phenytoin on or via lactation were
After birth, infants were transferred to a nursery for testing. They were        available.
tested at an age of about two weeks to 45 days (exact times were
corrected for gestational age, i.e., age based on conception date rather         2.5 Conclusions
than birth date). Infants exposed to phenytoin showed hyperexcitability
(jerking, screeching, refusing to attend to stimuli, lack of visual orientation) 2.5.1 Fertility
during cognitive testing when compared to stiripentol (p<0.05), not              No data are available on the effects of phenytoin on functional fertility
compared to phenytoin plus stiripentol.95                                        (ability to have children) of men or women. There are only some data on
                                                                                 changes in parameters related to fertility. The data regarding men concern
Intraperitoneal injection                                                        the effects of phenytoin on sperm characteristics and sexual interest and
                                                                                 function. The data regarding women are limited to effects on sexual
Rats                                                                             function and arousal.
Wolansky & Azcurra (2005) studied motor and learning disorders in                Sexual interest and function and serum levels of neuroactive hormones in
offspring (n= 28-32/group) of female Sprague Dawley rats treated                 men were investigated in one study.7 They were shown to be lower in men
intraperitoneally with 0 or 30 mg phenytoin sodium salt/kg bw/d during           with epilepsy treated with phenytoin.
GD13-18. Maternal body weights and behaviour, and gestation time were            Sperm characteristics were investigated in men with epilepsy treated with
not affected by the treatment (data not shown). Pup body weight was not          phenytoin by two research groups.8,9 These groups demonstrated a variety
affected either (data not shown). Circling velocities in a circular maze and     of changes: a lower seminal fluid volume, a decreased sperm
spatial error rates for direction of circling were increased in the phenytoin    concentration, an increased percentage of abnormal sperm, a decreased
group at all time points investigated (PND40, PND80 and PND150;                  sperm motility and a decreased duration of sperm activity. However, an
compared to controls, p<0.05). This study shows that gestational                 effect of epilepsy cannot be excluded, since similar effects were observed
exposure to phenytoin results in long-term functional disorders.96               in both untreated and phenytoin-treated epileptic patients. Sperm
                                                                                 characteristics were also investigated after in vitro incubation of sperm
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<pre>chapter 02 | Phenytoin                                                                                                              Phenytoin | page 49 of 81
with phenytoin.10,11 These studies produced contradictory findings.           In conclusion, the human data do not clearly indicate that male or female
Together, the data do not clearly indicate an adverse effect of phenytoin     fertility is affected by phenytoin. The same holds true for the animal data.
exposure on male fertility.                                                   Taken together, the human and animal studies do not provide sufficient
Sexual dysfunction, anxiety and arousal were examined in women with           evidence for classification. Therefore, the Committee recommends not
epilepsy treated with phenytoin.12 The investigators observed decreased       classifying phenytoin for effects on fertility due to a lack of appropriate
sexual function, increased anxiety and reduced arousal. An effect of          human data and data in experimental animals.
epilepsy cannot be excluded, because phenytoin-treated epileptic women
were compared with non/epileptic controls.Together, the data do not           2.5.2 Development
clearly indicate an adverse effect of phenytoin exposure on female fertility.
Overall, the human data are not sufficient for classifying phenytoin for      Developmental effects in humans
effects on fertility.                                                         The Committee has assessed the strength of the epidemiological
                                                                              evidence. It is clear that a large number of epidemiological studies has
In animal studies the effect of phenytoin on fertility was investigated in    been performed to examine the developmental effects of phenytoin. Many
male rats and female mice. In studies performed in male rats, no effects      of these studies have flaws, however. Only a subset concerns phenytoin
were seen on fertility at dose levels up to 30 mg/kg/day.65,66 At higher dose monotherapy, and is relatively well-designed and well-reported upon. In
levels of 80 mg/kg/day, close to the therapeutic range, an affected fertility these studies, various effects belonging to the foetal hydantoin syndrome
rate was reported, but no effects on reproductive organs, sperm               were found after prenatal exposure to phenytoin. These effects comprise
morphology and testosterone levels.67                                         major and minor structural defects, as well as functional and cognitive
At dose levels above 60 mg/kg/day pregnancy rate in mice was affected,        ones.
whereas no effect was seen on mating rate and number of implantations.68      Structural defects belonging to the foetal hydantoin syndrome were
This could have been a nonspecific effect of these dose levels, because       observed in a surveillance system study by Arpino et al. (2000)16, in
maternal mortality was increased.                                             prospective studies by D’Souza et al. (1990)32, Koch et al. (1992)28,
Together, the animal evidence is insufficient for classifying phenytoin for   Holmes et al. (2001)23 and Hernández-Diaz et al. (2012)18, in retrospective
effects on fertility.                                                         studies by Orup et al. (2003)39 and Lu et al. (2000)41, and Dean et al.
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<pre>chapter 02 | Phenytoin                                                                                                           Phenytoin | page 50 of 81
(2002)40, as well as in follow-up studies of pharmacovigilance centre data    hand, are small. Statistical analysis of the data was only possible in the
(Gladstone et al. (1992)35, Scolnik et al. (1994)36, Nulman et al. (1997)37). latter.
However, overlap of datasets in the last three studies cannot be ruled        The results of many other studies suggest that taking phenytoin during
out.35-37 Among the major malformations observed are spina bifida, cleft      pregnancy may lead to structural, functional and cognitive effects of the
lip/palate, hypospadias, extra digits, heart disease, hip dislocation and     foetal hydantoin syndrome in the offspring. These studies have major
megacolon. Minor malformations found include a high forehead, frontal         shortcomings, however, including combined exposure with other anti-
bossing, dental changes and nail and finger anomalies.                        epileptic drugs, lacking information as to co-exposure to such drugs,
Functional and cognitive effects of the foetal hydantoin syndrome were        absence of a control group, a small number of exposed women and
shown in three studies, by Arulmozhi et al. (2006)45, Scolnik et al.(1994)36  incomplete reporting, of statistics for example. Due to these limitations,
and Wide et al.(2002)52. These effects include delayed locomotor              the findings cannot be ascribed to prenatal phenytoin exposure with
development and a lower IQ. There is supportive evidence from a small IQ      certainty. Available data suggest that exposure to phenytoin can cause
study, demonstrating that verbal IQ is lower than non-verbal IQ in children   developmental effects like distal phalangeal and nail hypoplasia and
exposed prenatally.51                                                         hypertelorism. Many of the studies on minor congenital anomalies,
Although the studies mentioned above are the most informative ones, they      functional and cognitive effects have an additional flaw. Genetic factors
also have some weaknesses. Examples are the nature of the control             play a role in these outcomes. However, the parents often have not, or
groups and the size of the studies. The main or only control groups in the    only partly been examined for the same traits as the children. This also
prospective studies of D’Souza et al. (1990)32, Koch et al. (1992)28,         raises doubt as to prenatal phenytoin exposure being the cause of the
Nulman et al. (1997)37, Holmes et al. (2001)23 and Dean et al. (2002)40       effects observed.
consisted of children born to epileptic women not taking phenytoin. In the    Two well-performed, large studies provided no evidence for an excess risk
other studies, the control groups consisted of children born to               of developmental effects in children exposed to phenytoin in utero. These
non-epileptic women not taking phenytoin. Therefore, an effect of epilepsy    are the retrospective cohort studies by Forsberg et al. (2011)54 and by
in those studies cannot be excluded. The studies of D’Souza et al.            Samrén et al. (1999)42.
(1990)32, Koch et al. (1992)28 and Nulman et al. (1997)37, on the other       In addition to the many primary studies, three meta-analyses of the effects
                                                                              of maternal antiepileptic drug use on offspring development have been
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<pre>chapter 02 | Phenytoin                                                                                                            Phenytoin | page 51 of 81
reported: one on congenital malformations, one on congenital                 structural defects, i.e. cleft palate and diminished limb ossification, in
malformations and pregnancy outcomes, and one on neurological                offspring of mice exposed orally. Hansen & Billings (1986)77 reported
development.43,44,56 The results of these meta-analyses are in line with the decreased foetal growth. Furthermore, Vorhees et al. (1995)85, Elmazar
results of the primary studies, with the advantage of being based on larger  and Sullivan (1981)90 and Vorhees (1983)91 demonstrated a variety of
numbers. Meta-analyses have their own drawbacks, however. An                 functional effects in offspring of rats exposed orally. Among these effects
important one is that they cannot correct for the weaknesses of the          are impaired motor coordination and abnormal circling behaviour in water
original studies included.                                                   (more errors and longer time needed to find the goal). In all of these
Overall, there is a large amount of epidemiological data suggesting that     studies, maternal toxicity was absent.
phenytoin is a developmental toxicant and clinicians generally consider      Three studies in newborn mice also provide evidence for phenytoin
phenytoin a teratogen. Indeed, multiple studies show effects in terms of     causing functional developmental changes. These studies, by Ogura et al.
one or more features of the foetal hydantoin syndrome. All these studies     (2002)92, Ohmori et al. (1999)93 and Hatta et al. (1999)94, contribute such
have shortcomings however, minor or major ones. The Committee                evidence, because the murine neuronal system is still developing shortly
considers the quality of the human data insufficient to base the             after birth and known to be sensitive to developmental toxicity at this
classification of phenytoin primarily on the human data and classify         stage. The investigations with newborn mice extend the range of
phenytoin as a known human developmental toxicant.                           functional effects demonstrated to decreased motor coordination,
                                                                             hyperactivity, hypoactivity and impaired locomotor activity. These effects
Developmental effects in animals                                             were accompanied by lower weights of brain, cerebrum and cerebellum.
Many animal studies with phenytoin have been carried out, mainly             Additional evidence comes from two studies with intraperitoneal
involving oral or intraperitoneal administration to pregnant rats or mice.   administration of phenytoin to pregnant mice.77,80 The effects reported in
These studies show a variety of prenatal and postnatal effects on            the offspring were affected growth and occurrence of structural defects, in
development.                                                                 the absence of maternal toxicity. The effects observed were decreased
The Committee considers the oral studies to be the most relevant ones for    foetal weight and crown rump length, decreased transumbilical distance, a
assessing the safety of occupational (or other) exposure to phenytoin        higher number of foetal deaths and malformed foetuses, and increased
during gestation for offspring development. Fritz et al. (1976)74 reported   incidence of orofacial anomalies (cleft lip and palate).
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<pre>chapter 02 | Phenytoin                                                                                                           Phenytoin | page 52 of 81
The levels of phenytoin in plasma were measured in some of the studies      toxicant) and to label phenytoin with H360D (may damage the unborn
mentioned above.77,90,92,93 The concentrations found were in the range of   child).
human therapeutic levels (10-20 µg/mL).97,98
In the remaining animal studies maternal toxicity was observed, or          2.5.3 Lactation
information on its presence or absence was lacking. Therefore, the effects  There are only human data regarding the effects of phenytoin on or via
found in those studies, that are similar to those described above, might be lactation.
due to phenytoin, but cannot be ascribed to it with certainty.
Together, the animal studies provide sufficient evidence that prenatal      Effects via lactation
exposure to phenytoin can cause growth retardation, as well as              The analyses of effects via lactation were limited to IQ in breastfed
morphological and behavioural abnormalities. Some effects found are         children of women taking phenytoin. The studies did not show an adverse
identical to those observed in humans, the main one being cleft lip and     effect.57,58
palate. Many endpoints that can be investigated in animal tests differ from
those examined in humans. Taking this fact into account, the structural     Transfer via lactation and related risk of developmental toxicity
and functional developmental effects in animals are similar to those in     The majority of the human data concerns the transfer from maternal
humans.                                                                     plasma to breast milk.59-64 The milk to maternal plasma ratio reported
                                                                            ranges from six to 59 percent. The high upper value of this range is a
Overall conclusion on development                                           cause for concern. All transfer data concern women with epilepsy taking
The major effects of prenatal exposure to phenytoin in animals are similar  phenytoin breastfeeding their infants. The breastfeeding in this clinical
to those in humans, i.e. growth retardation and abnormalities in structural situation is often regarded as beneficial for the infant as it reduces
and functional development. Additionally, the serum levels producing        withdrawal symptoms in the child. During breast feeding, the infant
these effects in animals were within the commonly accepted therapeutic      gradually gains weight and, as a consequence, the dose of phenytoin
range for humans. Overall, the Committee is of the opinion that the         received (in mg/kg bw) is gradually decreasing. The high upper value of
available human and animal data are sufficient to recommend                 the milk to maternal plasma range suggests that breastfed infants of
classification of phenytoin in category 1B (presumed human reproductive     epileptic women taking phenytoin receive a dose postnatally that might
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<pre>chapter 02 | Phenytoin                                                                                                         Phenytoin | page 53 of 81
cause developmental toxicity. There are no data regarding the phenytoin      Proposed classification for developmental toxicity
plasma level of women only occupationally exposed to phenytoin. This         For developmental toxicity, the Committee recommends to classify
level will probably be much lower than that of epileptic women taking        phenytoin in category 1B (presumed human reproductive toxicant) and to
phenytoin. Consequently, withdrawal symptoms in their children, if any,      label it H360D (may damage the unborn child).
would presumably be lighter and more seldom.
One research group calculated that breast feeding leads to a daily           Proposed labelling for effects on or via lactation
phenytoin dose to the infant between 0.03 and 0.47 mg/kg bw.61 Assuming      For effects on or via lactation, the Committee recommends not labelling
a worst-case scenario, this dose range is still tenfold lower than the       phenytoin due to a lack of appropriate data.
therapeutic dose range for children (5-10 mg/kg bw).
As stated above, information on the phenytoin plasma level of women
exposed to phenytoin occupationally only, is not available. Therefore, it is
not possible to assess the risk of developmental toxicity these women
mediate through breastfeeding.
Overall conclusion on lactation
Overall, the Committee is of the opinion that, for the effects on or via
lactation, phenytoin should not be labelled due to a lack of appropriate
data.
2.5.4 Proposed classification and labelling
Proposed classification for fertility
For fertility, the Committee recommends not classifying phenytoin due to a
lack of appropriate data.
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<pre>References                                            Phenytoin | page 54 of 81
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<pre>Annexes                                              Phenytoin | page 68 of 81
annexes
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<pre>Annexes                                                                                                                                                                                   Phenytoin | page 69 of 81
A             animal fertility and developmental toxicity studies
Table 1. In vivo fertility studies
 Reference           Species          Experimental period/design                                     Dose and route          General toxicity                  Effects on reproductive organs/ effects on
                                                                                                                                                               reproduction
 Male fertility
 Shetty, 2007        Wistar rat       Epididymal sperm morphology was evaluated at 14 and            0, 3.5, 5.5 or 7.0      No information.                   No effects on epididymal sperm morphology.
                     (5/group)        35 days after a 5-day treatment period.                        mg phenytoin/
                                                                                                     rat/d, i.p.
 Cohn et al.,        Wistar rat       Fertility rate, reproductive organ weighs and sperm            0 or 20 mg              Growth not affected.              No effects on fertility rate, relative reproductive organ
 1982                (10 or 11/group) content and motility were evaluated after a 3-month            phenytoin/kg bw/d,                                        weights, epididymal sperm content or motility.
                                      treatment period (first dose at 3 wk PP).                      s.c.
 Cohn et al.,        Albino rat       Fertility rate, reproductive organ weights, epididymal         0, 5, 10 or 20 mg       Extensive cutaneous necrosis      Fertility rate decreased at 20 mg/rat (p<0.05).
 1978                (5 or 7/group)   sperm content and motility, Leydig cell count and blood        phenytoin/rat/d, s.c. at injection site.                  Other endpoints not affected.
                                      testosterone were evaluated after a 70-day treatment           (~ 20, 40 or 80
                                      period (age at start not reported).                            mg/kg bw/d).
 Female fertility
 Roberts et al.,     C57BL/6J and     Female mice were dosed every 48 hr from ≥1 week prior          0, 40, 65 or 105 mg     Mortality in non-pregnant C57     Fecundity index (% of mated females that became
 1991                A/J mice         to mating until sacrifice on GD18. Fertility endpoints         phenytoin sodium        females (1/11 at 65 mg/kg, 5/12   pregnant) decreased at 105 mg/kg in C57 mice (p<0.01),
                     (10-13/group)    comprised % of females that mated, fecundity index, total      salt/kg bw/day, p.o.    at 105 mg/kg, p<0.05) preceded    and dose-dependently in A/J mice, although only
                                      number of implantations per litter and number of live          (gastric intubation).   by weight loss and tremors.       statistically significant at the highest dose (p<0.01).
                                      implantations per litter.                                                                                                Other fertility endpoints not affected.
Table 2. In vivo developmental studies
 Reference          Species                          Experimental period/design           Dose and route               General toxicity                      Developmental toxicity
 Structural defects
 Rowland et al.,    Sprague-Dawley rats              Pregnant females were daily          p.o.: 0, 150, 375, 750,      Maternal death, impaired motor        • Embryolethality at 1,125 and 1,500 mg/kg.
 1990               (n=4-9/group).                   exposed orally at GD8-17.            1,125, or 1,500 mg/kg        function, decreased maternal          • Intrauterine growth retardation, associated with
                                                     reproductive outcomes were           bw/day.                      weight gain at 1,125 and 1,500          reductions in foetal weight at 375-1,135 mg/kg (p<0.05),
                                                     determined at GD20.                                               mg/kg.                                  crown-rump length at 750 and 1,125 mg/kg (p<0.05) and
                                                                                                                                                               appendicular and axial skeleton ossification.
                                                                                                                                                             • Craniofacial, cardiovascular and urogenital
                                                                                                                                                               malformations at 750 and 1,125 mg/kg (p<0.05).
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<pre>Annexes                                                                                                                                                                  Phenytoin | page 70 of 81
Zengel et al.,  Sprague-Dawley rats        Pregnant females were exposed by     p.o.: 0 or 1000 mg/kg    • Same average litter size (11).     • Pup mortality was higher in treated females (94%
1989            (group size not reported). gavage on GD9, -11 and -13.          bw/day of phenytoin      • Maternal toxicity not described.     compared to 1% in controls).
                                                                                suspended in 1%                                               • Offspring with symptoms of the foetal hydantoin
                                                                                carboxymethyl-cellulose.                                        syndrome; general growth reduction (p<0.01, 0.02 or
                                                                                                                                                0.05, at several time points) and changes in the
                                                                                                                                                craniofacial pattern (small head, hypertelorism, broad
                                                                                                                                                upturned nose, reduced cranial dimensions; p<0.005,
                                                                                                                                                0.01, 0.02 or 0.05).
Lorente et al., CD rats (group size not    Pregnant rats (1-5 litters/group)    p.o.: 700, 800 or 1000   The authors aimed to produce the     • Foetal onset growth retardation, abnormalities of the
1981            reported).                 were treated by gavage either on     mg phenytoin/kg bw/d.    greatest number of anomalies with      craniofacial region and axial skeleton at 1,000 mg/kg
                                           single or multiple days of gestation                          the lowest level of maternal           bw/d on GD9,11 and 13.
                                           in the periods GD9-11, GD9-13,                                mortality.                           • Lower foetal weights (p<0.05), a shortened snout and
                                           GD10-12, GD10-14, GD11-13,                                    Information on maternal mortality      high-arched, irregular palate, and delays in skeletal
                                           GD12-14 or GD13-15.                                           was not presented.                     maturation at 1,000 mg/kg bw/d on GD9, -11 and -13
                                                                                                                                                (p<0.05).
                                                                                                                                              • A 15% incidence of retarded palatal growth at single day
                                                                                                                                                administrations of 700-1,000 mg/kg bw.
Kim et al.,     Sprague/Dawley rats        Pregnant females were treated with   p.o.: 0, 50, 150, or 300 At 300 mg/kg, various signs of       At 300 mg/kg, developmental toxicity, including decreased
(2012)          (11/group).                phenytoin by gavage.                 mg/kg bw/day on GD6      maternal toxicity were observed:     foetal and placental weights (p<0.01), an increased
                                                                                through GD15.            increased clinical changes such as   incidence of morphological alterations (p<0.01) and a
                                                                                                         ataxia and seizure, suppressed body  delay in foetal ossification occurred (p<0.01 or p<0.05,
                                                                                                         weight and body weight gain          depending on the parameter). Developmental toxicity was
                                                                                                         (p<0.01), decreased food intake      less severe at 150 mg/kg bw/day than at 300 mg/kg
                                                                                                         (p<0.01), decreased absolute         bw/day. It was restricted to a decreased placental weight
                                                                                                         weights of lung, spleen, heart, and  (p<0.01), an increased incidence of visceral and skeletal
                                                                                                         brain and increased relative weights alterations (p<0.01), a decreased absolute maternal
                                                                                                         of adrenal glands, kidneys, brain,   weight of the heart and increased relative maternal
                                                                                                         ovary and liver as compared to the   weights of adrenal glands and brain. Maternal toxicity
                                                                                                         control group (p<0.01 or p<0.05,     signs similar to those at 300 mg/kg were present (p<0.01),
                                                                                                         depending on the organ). At 150      though less strong. No treatment-related developmental
                                                                                                         mg/kg bw/day, maternal toxicity      effects were observed at 50 mg/kg bw/day.
                                                                                                         signs similar to those at 300 mg/kg
                                                                                                         were present (p<0.01), though less
                                                                                                         strong: suppressed body weight and
                                                                                                         body weight gain, decreased food
                                                                                                         intake, a decreased absolute weight
                                                                                                         of the heart and increased relative
                                                                                                         weights of adrenal glands and brain.
                                                                                                         No treatment-related maternal
                                                                                                         effects were observed at 50 mg/kg
                                                                                                         bw/day.
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<pre>Annexes                                                                                                                                                                     Phenytoin | page 71 of 81
Eluma et al.,   CD 1 mice                  Pregnant mice were treated by         p.o.: 0, 50, 75 and 125   No information.                      • Time-dependent and dose-related decrease in foetal
1984            (2 mice/group/ time point; gavage during GD8-10, GD11-13,        mg phenytoin/kg bw/d.                                            weights in all treatment groups (p-values not
                6 mice per control group). GD14-16 or GD8-16.                                                                                     mentioned).
                                                                                                                                                • High incidence of cleft palate, and a lower incidence of
                                                                                                                                                  foetal death, cleft lips, haematomas, hydroencephaly
                                                                                                                                                  and exencephaly (p-values ranged from <0.001 to
                                                                                                                                                  <0.0001) Lesions were not specified per time point and
                                                                                                                                                  dose level.
Fritz et al.,   (Tif/MAG) mice             Mated mice were treated by gavage p.o.: 0, 15, 50, 100 or       • Ten high-dose dams died.           • Early embryonic death at 100 and 170 mg/kg.
1976            (n=30/group).              during GD6-15.                        170 mg phenytoin/kg       • No maternal mortality in the lower • Reduced mean foetal weight at 100 and 170 mg/kg
                                           Offspring was subjected to visceral bw/d.                         dose groups.                         (p<0.01).
                                           (one third) and skeletal examination                            • Food intake diminished at          • Dose-related increase in cleft palate at 15, 50, 100 and
                                           (two thirds).                                                     100 mg/kg.                           170 mg/kg bw/d (0.3%, 2%, 5.2% and 9.3%,
                                                                                                           • No effect on mortality or food       respectively, versus 0.13% in historical control data from
                                                                                                             intake at 15 or 50 mg/kg.            500 mice) (statistically significant from 50 mg/kg bw/d
                                                                                                                                                  onwards, p<0.01).
                                                                                                                                                • Incomplete ossification of the fore-limbs at 170 mg/kg
                                                                                                                                                  bw/d (p<0.01), but no malformations.
Roberts et al.  C57BL/6J and A/J mice      Female mice were dosed every 48       p.o.: 0, 40, 65 or 105 mg Mortality in non-pregnant C57        • Decreased post-implantation loss in A/J mice at 65 mg/
1991            (10-13/group).             hr from ≥1 week prior to mating until phenytoin sodium          females (1/11 at 65 mg/kg, 5/12 at     kg (p<0.05).
                                           sacrifice on GD18. Gestational        salt/kg bw/day, p.o.      105 mg/kg), preceded by weight       • Dose-dependent decrease (≥40 mg/kg) gestational
                                           weight gain, gravid uterus weight,    (gastric intubation).     loss and tremors.                      weight gain and gravid uterus weight in C57 (linear trend
                                           foetal weight and visceral and                                                                         analysis p<0.05).
                                           skeletal observations were                                                                           • Decreased foetal weight in C57 (at 65 mg/kg, p<0.05).
                                           recorded.                                                                                            • Decreased ossification in both strains at 65 mg/kg.
                                                                                                                                                • Increased frequency of hydroencephaly (65 mg/kg) and
                                                                                                                                                  open eyelid (40 and 65 mg/kg) in A/J, cardiac calcium
                                                                                                                                                  deposit (40 mg/kg) in C57 mice (all p<0.05).
Khera, 1979     Cats (n=13-14/group).      Mated cats were treated by gavage p.o.: 0, 1 or 2 mg            Decreased maternal body weights      • No effects on abortion, non-pregnancy, live or dead
                                           during GD10-22, and necropsied on phenytoin sodium              at 2 mg/kg bw/d on GD20 and            foetuses or mean foetal weights.
                                           GD 43.                                salt/kg bw/d.             GD30 (p<0.05), normal body           • Increased number of resorptions at 2 mg/kg bw/d
                                           Foetuses were examined for                                      weights at 1 mg/kg bw/d.               (p<0.05).
                                           external, visceral and skeletal                                                                      • No anomalies in live foetuses, but a high incidence of
                                           malformations.                                                                                         malformations in cats aborting on GD31-37; (all 11
                                                                                                                                                  foetuses from two cats given 1 mg/kg bw/d had cleft
                                                                                                                                                  palate and open eyelids and of the 10 foetuses from one
                                                                                                                                                  cat given 2 mg/kg bw/d, four had umbilical hernia and
                                                                                                                                                  one had open eyelids).
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<pre>Annexes                                                                                                                                                                       Phenytoin | page 72 of 81
Finnell et al., SWV, LM/Bc, and C57BL/6J     Virgin mice daily exposed orally via    p.o.: 0, 10, 20, 40, or 60 Not reported.                       • Foetal weight was dose-dependently decreased in all
1989            mice (10-15 litters/         drinking water 15-days before           mg phenytoin/kg bw.                                              strains (p<0.05).
                treatment).                  mating and throughout gestation                                                                        • The incidence of offspring with one or more congenital
                                             (until GD18).                                                                                            abnormalities was increased dose-dependently in all
                                                                                                                                                      mice strains (p<0.05).
                                                                                                                                                    • Skeletal defects included mainly a pattern of multiple
                                                                                                                                                      malformations and ossification delays in supraoccipital
                                                                                                                                                      bones, sternebrae, distal phalanges and midfacial
                                                                                                                                                      bones.
                                                                                                                                                    • Soft tissue defects included mainly dilated or immaturely
                                                                                                                                                      developed cerebral ventricles and renal defects, digital,
                                                                                                                                                      cardiac and ocular anomalies.
                                                                                                                                                    • Correlation between risk of abnormalities and plasma
                                                                                                                                                      phenytoin (p<0.05).
Hansen and      A/J mice.                    Pregnant females were exposed           p.o.: 0, 60 or 75 mg/kg    No maternal toxicity, indicated by  • Decreased foetal weight at both doses (p<0.05)
Billings, 1986                               orally via the feed daily, prior to and phenytoin.                 food consumption, weight gain rate, • Decreased number of implantation sites in the highest
                                             during gestation.                                                  sedation and ataxia (data not         dose group (p<0.05).
                                                                                                                shown).
Soysal et al.,  Wistar albino rats (test     Pregnant females were treated i.p.      i.p. 25 mg/kg phenytoin    Not reported.                       • Mean length (2.75±0.29 cm) and weight (3.04±0.42 g) of
2011            group: n=42 foetuses from 7  on GD 8, 9 and 10. Foetuses were        diluted with serum                                               foetuses from drug-treated animals were different from
                litters, control group: n=40 isolated on GD 20 and examined          physiologic.                                                     the control group (length 3.21±0.27 cm and weight
                foetuses from 6 litters).    for bone and cartilage defects.                                                                          3.51±0.35 g; p<0.001).
                                                                                                                                                    • Increased costal separation in 10/42 foetuses from drug
                                                                                                                                                      treated animals.
                                                                                                                                                    • Shape malformations in the ribs of foetuses from drug-
                                                                                                                                                      treated animals.
Shapiro et al., Sprague-Dawley rat.          Dams were dosed from GD17               0, 10, 50 or 100 mg        No information.                     • Decreased body weights from birth throughout life at 50
1987                                         through day 7 PP. Weights of testis     phenytoin sodium                                                 or 100 mg/kg (p<0.05).
                                             and seminal vesicle, and serum          salt/kg bw/day, i.p.                                           • Decreased relative testis weights at day 8 PP in male
                                             hormone levels (andro-stenedione,                                                                        offspring at 10 and 50 mg/kg (p<0.002 and p<0.02,
                                             testosterone, dihydrotestosterone)                                                                       respectively), but not at days 28 or 120 PP. No data for
                                             were evaluated in male offspring of                                                                      the 100 mg/kg group.
                                             8, 28 or 120 days of age.                                                                              • Relative seminal weight was decreased at day 120 PP
                                                                                                                                                      at 50 and 100 mg/kg (p<0.02 and p<0.001, respectively).
                                                                                                                                                    • Serum levels testosterone and dihydrotestosterone in
                                                                                                                                                      male offspring were not affected at days 8, 28 or 120 PP.
                                                                                                                                                      Levels of androstenedione at 50 mg/kg were increased
                                                                                                                                                      at day 8 PP (p<0.02), and decreased at day 28 PP
                                                                                                                                                      (p<0.02).
                                                                                                                                                    • Estrous cyclicity (vaginal smears from about 13-week
                                                                                                                                                      old offspring) and weights of the uterus and ovaries (at
                                                                                                                                                      about 16 weeks PP) in female offspring not affected.
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<pre>Annexes                                                                                                                                                                     Phenytoin | page 73 of 81
Hansen &         A/J mice.                       Pregnant females were i.p. injected i.p.: 0, 60 or 75 mg/kg   sedation and ataxia (high-dose     • A dose-related increase in resorptions (p<0.05)
Billings, 1986                                   with phenytoin on GD10.             phenytoin.                group).                            • Nearly all surviving foetuses had an abnormality, mainly
                                                                                                                                                    cleft lip and palate (p<0.05).
Hansen &         ICR mice                        Pregnant mice were treated by i.p.  i.p.: 0, 50, 75 or 100 mg • The high-dose was lethal to the  • Dose-related decrease in mean foetal weight and crown
Hodes, 1983      (25/group).                     injection on GD10-12.               phenytoin/kg bw/d.          dams and omitted from the study.   rump length in both test groups (p<0.01 or p<0.05).
                                                                                                               • No maternal toxicity at 50 and   • Increased transumbilical distance at 75 mg/kg bw/d
                                                                                                                 75 mg/kg bw/d (measures not        (p<0.01).
                                                                                                                 specified).                      • Increased incidence of malformed foetuses at 75 mg/kg
                                                                                                                                                    bw/d (p<0.05), with orofacial anomalies most frequently
                                                                                                                                                    observed (p<0.01).
                                                                                                                                                  • Other malformations included ectopic kidneys,
                                                                                                                                                    cryptorchydism and cardiac defects, but no data were
                                                                                                                                                    presented..
                                                                                                                                                  • No skeletal defects in any group.
                 C57BL/6J, B6AF1, AB6F1,                                             i.p.: 0 or 75 mg/kg bw/d.                                    A higher number of resorptions was observed in two
                 (B6A)F2 and C3H/He mice                                                                                                          strains, a higher number of malformed foetuses in three
                 (15, 19 or 20 animals per                                                                                                        strains, a higher number of orofacial anomalies in two
                 group).                                                                                                                          strains and a lower foetal weight in three strains treated
                                                                                                                                                  with phenytoin as compared to control animals (p<0.01 or
                                                                                                                                                  p<0.05).
Rowland et al.,  Sprague-Dawley rats             Pregnant females were daily         i.v.: 0, 25, 50, 75, or   No decreased weight gain, mild to  • Embryolethality
1990             (n=4-9/group).                  exposed intravenously at GD8-17.    100 mg/kg bw/day.         severe imbalance and ataxia at     • Intrauterine growth retardation, associated with
                                                 Reproductive outcomes were                                    50and75 mg/kg, excessive ataxia at   reductions in foetal weight and crown-rump length
                                                 determined at GD20.                                           100mg/kg (100 mg/kg therefore        (p<0.05).
                                                                                                               discontinued).                     • Craniofacial malformations (p<0.05).
Functional and cognitive defects
Mowery et al.,   Sprague Dawley rats             Female rats were dosed by gavage    p.o.: 0 or 50 mg          • No information on maternal       • Increased performance in simple associative learning
2008             (test group: n=31 from 11       twice daily from 10 days before     phenytoin/kg bw/d.          toxicity.                          tasks (appetitive-to-aversive transfer paradigm, p<0.05).
                 litters; controls: n=22 from 10 mating, throughout pregnancy and    Maternal plasma levels                                       • Impaired performance in a higher-order learning and
                 litters).                       the three week pre-weaning period.  on the last day of dosing                                      memory task (avoidance conditioning, p<0.05).
                                                 Behavioural testing was conducted   approximated the low
                                                 with 80-90 days old female          level of human
                                                 offspring.                          therapeutic
                                                                                     concentrations
                                                                                     (10-20 µg/ml).
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<pre>Annexes                                                                                                                                                                   Phenytoin | page 74 of 81
Schilling et al., Sprague Dawley rats           Pregnant Sprague Dawley rats         p.o.: 0 or 200 mg     • Decreased maternal body weight    • Circling in 53% of the exposed offspring; no circling in
1999              (10 (controls) or 15 (treated were dosed by gavage during          phenytoin/kg bw/d.      during GD14-18 (p<0.05).            the control group.
                  dams)).                       GD7-18. Per litter, 2 male offspring                       • Increased offspring mortality     • Impaired reference memory-based spatial learning in the
                                                were tested in the Morris water                              during the first week (p<0.01).     Morris water maze in noncircling offspring (p<0.01).
                                                maze, one exhibiting circling in a                         • Preweaning body weights not       • Impaired reference memory based spatial learning,
                                                straight water channel and one in a                          affected.                           impaired cued (visible) platform learning (p<0.01),
                                                circling tank.                                             • Decreased post weaning body         impaired spatial discrimination (p<0.01) and impaired
                                                                                                             weights (p<0.05, or <0.01).         working memory-based learning (p<0.01) in circling
                                                                                                                                                 offspring.
McCartney et      Sprague Dawley rats (≥20      Pregnant Sprague Dawley rats (≥20 p.o.: 0, 50, 100 or 150  • Dose-related reduction in         • Accelerations in developmental landmarks and
al.,1999.         dams/group). Examinations     dams/group) were dosed by gavage mg phenytoin sodium         maternal weight gain in all         preweaning behaviour (eye opening, incisor eruption,
                  were conducted in all pups    during GD 7-18.                      salt/kg bw/d.           treatment groups (p<0.05).          negative geotaxis and olfactory orientation) in pups of all
                  (pre-weaning) or in 1 pup/                                                               • Increased incidences of             treatment groups (p<0.05).
                  sex/ litter (post-weaning).                                                                chromodacryorrhea, lacrimation    • Delays in air righting in pups of all offspring treatment
                                                                                                             and circling at 100 and 150 mg/kg   groups (p<0.05).
                                                                                                             bw/d (data not reported).         • Increased locomotor activity in high-dose pups (at
                                                                                                                                                 PND21) and adults (at PND62) (p<0.05).
                                                                                                                                               • Dose-related performance deficits in a water maze
                                                                                                                                                 assay (learning/ memory impairments, p<0.01) and in
                                                                                                                                                 auditory startle responses (p<0.05 in at least one dose
                                                                                                                                                 group).
                                                                                                                                               • Reduced hind brain weights in male pups at 150 mg/kg
                                                                                                                                                 bw/d (p<0.05).
                                                                                                                                               • Reduced forebrain and whole brain weights in adult
                                                                                                                                                 females at 100 and 150 mg/kg bw/d (p<0.05).
Tsutsumi et al.,  Sprague Dawley rats (7-10     Pregnant rats were dosed by          p.o.: 0, 50 or 100 mg • No information on maternal        • Delayed time completion of a negative geotaxis (reflex)
1998              dams/group) Examinations      gavage during GD 7-18, and male      phenytoin/kg bw/d.      toxicity.                           test in both treatment groups (p<0.001).
                  were conducted in             offspring was subjected to a reflex                                                            • No effects in a figure-eight-maze, a Biel water maze, or
                  (generally) 10-15 offspring   test and several learning/memory                                                                 a Morris maze test.
                  males/group.                  tests.                                                                                         • High total number of choices (p<0.05).and low number
                                                                                                                                                 of correct choices (p<0.05).in the high-dose group in
                                                                                                                                                 radial maze test.
                                                                                                                                               • Low number of correct choices in the high-dose group in
                                                                                                                                                 delayed nonmatching-to-sample test (T-shaped maze,
                                                                                                                                                 p<0.05.).
                                                                                                                                               • Decreased offspring whole brain weights in high dose
                                                                                                                                                 group in wk 6 (p<0.05); body weigths unaffected.
                                                                                                                                                 Offspring brain weight had returned to normal at 16
                                                                                                                                                 weeks.
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<pre>Annexes                                                                                                                                                                           Phenytoin | page 75 of 81
Vorhees et al., Sprague Dawley rats (5-6      Pregnant rats were dosed by          p.o.: 0 or 100 mg           • Maternal weight gain, gestation     • More errors and longer latencies to find the goal in the
1995            dams/group) (Offspring        gavage during GD7-18.                phenytoin sodium              length, pups per litter and sex       Cincinnati (water) Maze (circling animals p<0.01),
                number tested was not         Offspring was tested at              salt/kg bw/d in corn oil.     ratio within litters were not         noncircling animals p<0.05).
                indicated).                   approximately 50 days of age.                                      affected.                           • The effect in circling animals was larger than in
                                                                                                                                                       noncircling animals.
Pizzi et al.,   Sprague Dawley rats (10-11    Pregnant rats were dosed by          p.o.: 0, 100 or 200 mg      • Dose-related decrease in            • Increased pivoting locomotor activity on PND7 and 9 at
1992            dams/group).                  gavage during GD9-18.                phenytoin sodium              maternal weight gain (both doses      100 mg/kg bw/d (due to mortality, the 200 mg/kg bw/d
                                                                                   salt/kg bw/d.                 p<0.001).                             group was not examined).
                                                                                   (On GD18, maternal          • Lower birth weights and body        • Abnormal spontaneous circling behaviour (2 and 33% in
                                                                                   plasma levels in the          weights at PND30 (high dose           the low- and high-dose group, respectively).
                                                                                   low- and high-dose            group males and females             • Increases in locomotor activity measures in adult rats
                                                                                   group were 11.5 and           p<0.001; low dose group males         that had been exposed to 200 mg/kg bw/d (at PND45:
                                                                                   26.2 mg¹ phenytoin/ml).       p<0.05)., and increased offspring     p<0.05; at PND66: p<0.05).
                                                                                                                 mortality (41% and 61% in the
                                                                                   ¹ The Committee assumes       lowand high-dose group,
                                                                                   that µg rather than mg was    respectively).
                                                                                   meant.                      • Exposed offspring frequently
                                                                                                                 showed chromodacryorrhea.
Weisenburger    Sprague Dawley rats (10-13    Pregnant rats were dosed by          p.o.: 0, 100 or 200 mg      • Reduced maternal weight gain in     • Dose-related increases in circling behaviour (both
et al., 1990    litters/group).               gavage during GD7-18.                phenytoin/kg bw/d.            both treatment groups (p<0.05).       doses: p<0.01), preweaning locomotor activity (both
                Where possible, six offspring                                      Maternal serum concen- • Increased pup mortality at 200             doses: p<0.05), errors in a complex water maze and
                rats/sex/litter were retained                                      trations on GD18 were         mg/kg bw/d at birth (p<0.01),         impaired performance in a radial-arm maze (both circlers
                for testing.                                                       15.1 and 20.9 µg/ml for       PND7 (p<0.01).and PND28               and noncirclers at each dose: p<0.01).
                                                                                   low- and high-dose,           (p<0.05).
                                                                                   respectively which was      • Reduced preweaning and
                                                                                   stated to be in the range     postweaning offspring body
                                                                                   of human therapeutic          weights at 200 mg/kg bw/d
                                                                                   ranges (10-25 µg/ml).         (p<0.05).
Vorhees, 1987   Sprague Dawley rats (13-20    Pregnant rats (13-20 litters/group)  p.o.: 0, 100, 150 or 200    • Decreased maternal weights in       • Dose-related increase in circling behaviour (p<0.05 or
                litters/group) (Offspring     were dosed by gavage during          mg phenytoin/kg bw/d          the high-dose group during            <0.01).
                number tested per group was   GD7-18.                              • These levels resulted       gestation (at GD18 p<0.01, at       • The highest dose produced:
                not indicated).               Offspring of both sexes was tested     in maternal plasma          GD20 p<0.05).                         - increased activity (in various tests of activity, p<0.01),
                                              prior to weaning (for activity only)   levels on GD 18 (4h       • 23% of the litters in the high-dose   - delayed dynamic righting development (p<0.01),
                                              and afterwards.                        after dosing) of about      group were lost (versus 7% in         - impaired Biels (multiple-T water) maze learning
                                                                                     10, 20 and 24 µg/ml,        controls, not statistically             (p<0.01),
                                                                                     in the low-, mid- and       significant).                         - Y-maze (avoidance) learning (p<0.05),
                                                                                     high-dose group,          • Increased offspring mortality in      - inhibited tactile startle responses (p<0.05).
                                                                                     respectively (with little   the high-dose group during          • The two lower doses showed a dose-effect relationship
                                                                                     decline up to 24h).         PND1-21 (p<0.01).                     on most measures.
                                                                                                                                                     • No effects on postnatal growth, total brain weight, or
                                                                                                                                                       brain protein content in adulthood (at 79-84 days of
                                                                                                                                                       age).
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<pre>Annexes                                                                                                                                                             Phenytoin | page 76 of 81
Ruiz et al.,   Sprague Dawley rats           Rats were dosed by gavage, from       p.o.: 0 or 50 mg   • No information on maternal      • No major differences in cortical layers III and IV.
1987           (6 offspring/group).          7 days before fertilization,          phenytoin/kg bw/d.   toxicity.                       • Total cell density in layer V higher (p<0.0001).
                                             throughout pregnancy, while pups                                                           • Numbers and lengths of apical and basal dendrites
                                             were also given the drug by                                                                  decreased (p<0.05 to p<0.0001)
                                             gavage. The dosing regimen was                                                             • Diminished degree of neuronal maturation at the level of
                                             not reported.                                                                                collateral apical dendrites of pyamidal cells in the surface
                                             Neuronal structure in the                                                                    layers of the cortex.
                                             somatosensory cortex at 30 days                                                            • Poor development of the basilar dendrites in the deeper
                                             of postnatal development was                                                                 layers of the sensory cortex.
                                             investigated.                                                                              • Altered pattern of phosphorylation of cytoskeletal proteins.
Elmazar &      Wistar rats (10 (first study) Pregnant rats were dosed by           p.o.: 0 or 100 mg  • Decreased body weights of the   • Lower survival and decreased body weights in two
Sullivan, 1981 - 20 (repeat study)           gastric intubation during GD7-19.     phenytoin/kg bw/d.   treated dams up to GD10.          experiments at PND2 (p<0.05), in one of them at PND21
               litters/group).               After parturition, the offspring was                     • Due to paired feeding, the body   (p<0.01).and PND90 (p<0.05).
                                             culled to six-eight/litter and reared                      weights of the control dams     • Delay of up to 15 days in the development of the
                                             by fostering or cross fostering.                           followed the same pattern.        dynamic righting reflex (no statistics reported).
                                                                                                                                        • Decreased ability of offspring to stay on a rotating rod
                                                                                                                                          (p<0.05).
                                                                                                                                        • Decreased ability to walk along elevated parallel rods
                                                                                                                                          (p<0.01).
                                                                                                                                        • No changes in development of physical landmarks, or in
                                                                                                                                          the development of crawling and walking activities at
                                                                                                                                          9-21 days of age, and no changes in a head-dipping test
                                                                                                                                          or in a conditioned avoidance test (shuttle box) at 26-34
                                                                                                                                          days of age.
                                                                                                                                        • Decreased absolute brain weight at 3 d (p<0.05 or
                                                                                                                                          <0.001), which remained until 90 d (p<0.001).
                                                                                                                                        • No differences in cerebellar DNA content.
Vorhees, 1983  Sprague-Dawley rats           Pregnant rats received phenytoin or
               (number not reported).        vehicle by gavage. Structural
                                             effects and postnatal functioning
                                             were investigated on GD20 or
                                             postnatally. The first experiment
                                             served to determine the highest
                                             dose for assessing postnatal
                                             functional teratogenesis in
                                             experiments 2 and 3. In this dose
                                             range-finding study 200 mg/kg
                                             bw/ day was chosen as the highest
                                             dose to be used in the other
                                             experiments. This choice was
                                             based on maternal toxicity (reduced
                                             maternal weight, p<0.01) and the
                                             fraction of resorbed or dead
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<pre>Annexes                                                                                                                                                             Phenytoin | page 77 of 81
                                  foetuses (not statistically different
                                  from controls).
                                                                        Experiment 2: 0, 5, 50 or • Decreased maternal body weight      • No effects on lower incisor eruption, eye opening or
                                                                        200 mg/kg bw/day p.o.       at 200 mg/kg bw/day on GD14           vaginal patency development.
                                                                        on GD7-18.                  and -18 (p<0.05), and during        • No effects on preweaning negative geotaxis, olfactory
                                                                                                    lactation (p<0.01).                   orientation, figure-8 activity or neonatal T-maze behaviour.
                                                                                                  • Length of gestation, external       • Effects on preweaning righting (data not shown), pivoting
                                                                                                    malformations, number of offspring    (200 mg/kg, p<0.001), startle (200 mg/kg, p<0.001), and
                                                                                                    delivered and sex ratio within        swimming (200 mg/kg, at various ages, p<0.05).
                                                                                                    litters not affected.               • No effects on postweaning M-maze behaviour, passive
                                                                                                  • Offspring mortality increased at 50   avoidance or spontaneous alternation.
                                                                                                    and 200 mg/kg bw/day on PND0        • Postweaning figure-8 activity and Biel water maze
                                                                                                    (both p<0.0001) and at 200 mg/kg      learning affected (200 mg/kg bw/day, p<0.05 to p<0001).
                                                                                                    bw/day on PND 21 (p<0.001).
                                                                                                    Mortality returned to normal on
                                                                                                    PND22-70.
                                                                                                  • Before weaning (PND1-21), no
                                                                                                    reduction in offspring body weight
                                                                                                    in any dose group (data not
                                                                                                    shown).
                                                                                                  • After weaning (PND22-70),
                                                                                                    offspring body weight was
                                                                                                    reduced: 200 mg/kg group 10.8%
                                                                                                    lighter than controls on PND42
                                                                                                    (p<0.001) and 7.2% lighter on
                                                                                                    PND70 (p<0.05).
                                                                        Experiment 3: 0 or 200    • Maternal weight not affected.       • No effects on incisor eruption, eye opening or vaginal
                                                                        mg/kg bw/ day p.o. on     • Length of gestation, external         patency development.
                                                                        GD7-10, 11-14 or 15-18.     malformations, number of offspring  • No effects on preweaning righting, negative geotaxis,
                                                                                                    delivered and sex ratio within        olfactory orientation, figure-8 activity or neonatal T-maze
                                                                                                    litters not affected.                 behaviour.
                                                                                                  • Offspring mortality increased       • Increased preweaning pivoting locomotion and delayed
                                                                                                    preweaning after treatment at         swimming development in the groups exposed at
                                                                                                    GD7-10 (p<0.001) and GD15-18          GD11-14 or GD15-18 (p<0.05 or <001); startle not
                                                                                                    (p<0.01).                             affected.
                                                                                                  • Offspring mortality increased       • No effects on postweaning M-maze behaviour or
                                                                                                    postweaning after treatment at        spontaneous alternation.
                                                                                                    GD11-14 (p<0.01).                   • Increased postweaning figure 8 ambulation (p<0.01) and
                                                                                                                                          water maze errors (p<0.001) and impaired passive
                                                                                                                                          avoidance retention in the GD11-14 exposure group
                                                                                                                                          (p<0.05).
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<pre>Annexes                                                                                                                                                                      Phenytoin | page 78 of 81
Ogura et al.,   C57BL/6 mice (13-15 males/    Newborn mice were dosed by            p.o.: 0 or 35 mg         • In some pups: acute behavioural    • Reduced brainstem weight, cerebral weight, cerebellar
2002            group).                       gavage during PND5-14.                phenytoin/kg bw/d -        detoriation, including anorexia,     weight and total brain weight in 56 days old mice
                                                                                    Plasma level of            hyperactivity and motor              (p<0.01).
                                                                                    phenytoin was 20±2.8       coordination deficits.             • Interference with the development of granule cells in the
                                                                                    µg/ml, 3h after the last • Mortality (38%).                     hippocampus and the cerebellum, and with the dendritic
                                                                                    dose.                    • Weight loss (at 56 days, the body    development of Purkinje cells.
                                                                                    • Brain concentration of   weights of treated mice had        • Impaired acquisition of a hidden platform task in a water
                                                                                       phenytoin was 1.6       returned to control values).         maze test (p<0.001).
                                                                                       times higher                                               • Increased errors during learning in a radial arm maze
                                                                                       (31.9±10.3 µg/ml).                                           (p<0.01).
Ohmori et al.,  Jcl:ICR mice (13-16/sex/      Phenytoin was administered by         p.o.: 0 or 35 mg         • Mortality >30% in males and        • Impaired motor performance in a rotating rod (p<0.05).
1999            group).                       gavage to newborn Jcl:ICR mice        phenytoin/kg bw/d          females.                           • Impaired spontaneous locomotor activity (p<0.01).
                                              during PND2-4.                        Plasma level of          • Weight loss, anorexia, motor       • Reduced total brain weight, cerebral weight and
                                                                                    phenytoin on the third     hypoactivity and incoordination at   cerebellar weight (p<0.01).
                                                                                    day of administration      PND4 (data not shown). Body        • Neurotoxic damage in the developing cerebellum (cell
                                                                                    was 17.7 µg/ml. In the     weight recovered to normal at        death of external granule cells, inhibited migration of
                                                                                    brain the level was        PND56.                               granule cells and impaired Purkinje cell differentiation).
                                                                                    higher (31.4 µg/g).
Hatta et al.,   Jcl:ICR mice                  Newborn mice were dosed by            p.o.: 0, 10, 17.5, 25 or • 8% mortality rate in the high-dose • Decreased locomotor abilities and righting reflex at 25 or
1999            (n not indicated).            gavage on PND2-4.                     35 mg phenytoin/kg         group in either sex.                 35 mg/kg bw/d, on PND5 (p<0.05 or <0.01).
                                                                                    bw/d.                    • No effects on pup body weights     • Decreased total brain weight, cerebral weight and
                                                                                    Dose levels were stated    (PND5-PND21).                        cerebellar weight at 25 or 35 mg/kg bw/d (p<0.05 or
                                                                                    to correspond to                                                <0.01).
                                                                                    therapeutic plasma
                                                                                    levels in humans.
Phillips and    Monkeys (Macaca               Adult female monkeys (Macaca          By stomach catheter at   • No information on maternal         • Infants showed hyperexcitability (jerking, screeching,
Lockard, 1993   fascicularis).                fascicularis) were dosed via          levels providing plasma    toxicity.                            refusing to attend to stimuli, lack of visual orientation)
                (Four adult females were      stomach catheter from 1 month         concentrations between                                          during cognitive testing when compared to stiripenol
                dosed; control groups         before mating throughout gestation.   4-12 µg phenytoin/ml                                            (p<0.05), not to phenytoin plus stiripenol.
                consisted of monkeys treated  After birth, the infants were         (initial dose was 20
                with stiripenol (n=5), or     transferred to a nursery for testing. mg/kg bw).
                phenytoin plus stiripenol     They were tested at an age of
                (n=4), because stiripenol has about 2 weeks to 45 days (exact
                been shown to reduce the      times were corrected for gestational
                incidence of phenytoin-       age, i.e., age based on conception
                induced congenital            date rather than birth date).
                malformations in mice.)
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<pre>Annexes                                                                                                                                                            Phenytoin | page 79 of 81
 Wolansky &      Sprague Dawley rats         Pregnant females were treated        i.p.: 0 or 30 mg      • Maternal body weights and pup   • Increased circling velocities in a circular maze at all time
 Azcurra, 2005   (n= 28-32 offspring/group). during GD 13-18. Motor and           phenytoin sodium        body weights not affected (data   points (p<0.05).
                                             learning disorders of offspring were salt/kg bw/d.           not shown).                     • Increased spatial error rates for direction of circling at all
                                             examined in a circular maze at                             • Maternal behaviour not affected   time points (p<0.05).
                                             PND40, PND80 and PND150.                                     (data not shown).
                                                                                                        • Gestation time not affected.
B          abbreviations                                                                           n         number
                                                                                                   NOEL no observed effect level
bw         body weight                                                                             NOAEL no observed adverse effect level
CI         confidence interval                                                                     OR        odds ratio of an effect in exposed population versus non exposed
d          day                                                                                               population
GD         gestation day                                                                           PND       postnatal day
h          hours                                                                                   PP        post partum day
i.m.       intramuscular                                                                           p.o.      oral
i.p.       intraperitoneal                                                                         RR        relative risk
i.v.       intravenous                                                                             s.c.      subcutaneous
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<pre>The Committee                                                                                                                Phenytoin | page 80 of 81
         the Committee                                                   Structurally consulted expert
                                                                         • AH Piersma, Professor of reproductive and developmental toxicology,
This advisory report has been prepared by the Subcommittee on the           Utrecht University; National Institute of Public Health and the
Classification of Substances Toxic to Reproduction, a permanent             Environment, Bilthoven
subcommittee of the Health Council of the Netherlands.
The first draft of this report was prepared by M.M. Tegelenbosch-        Scientific secretary
Schouten, M. Sc, in cooperation with Dr. M.J.W. van den Hoven,           • PW van Vliet, Health Council of the Netherlands, Den Haag
Dr. D. Jonker and Dr. B.A.R. Lina, Department Toxicology and Applied
Pharmacology, TNO Quality of Life, Zeist.
Chair
• D Lindhout, Emeritus professor of Medical Genetics; paediatrician (not
   practising), clinical geneticist; University Medical Center Utrecht
Members
• N Roeleveld, Reproductive epidemiologist; Radboud university medical
   center, Nijmegen
• JG Theuns-van Vliet, Reproductive toxicologist, Triskelion BV, Zeist
• TGM Vrijkotte, Epidemiologist, AMC, Amsterdam
• ECM Tonk, Regulatory toxicologist, Charles River Laboratories Den
   Bosch BV (since 1 January 2018)
• DH Waalkens-Berendsen, Reproductive toxicologist; Zeist (until 15
   September 2017)
• PJJM Weterings, Toxicologist; Weterings Consultancy BV, Rosmalen
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<pre>The Health Council of the Netherlands, established in 1902, is an independent scientific advisory body. Its remit is “to advise the government and
Parliament on the current level of knowledge with respect to public health issues and health (services) research...” (Section 22, Health Act).
The Health Council receives most requests for advice from the Ministers of Health, Welfare and Sport, Infrastructure and Water Management, Social
Affairs and Employment, and Agriculture, Nature and Food Quality. The Council can publish advisory reports on its own initiative. It usually does this in
order to ask attention for developments or trends that are thought to be relevant to government policy.
Most Health Council reports are prepared by multidisciplinary committees of Dutch or, sometimes, foreign experts, appointed in a personal capacity.
The reports are available to the public.
This publiation can be downloaded from www.healthcouncil.nl.
Preferred citation:
Health Council of the Netherlands. Phenytoin. Evaluation of the effects on reproduction,
recommendation for classification. The Hague: Health Council of the Netherlands, 2018;
publication no. 2018/15.
All rights reserved
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