Transplacental passage of oxcarbazepine and its metabolites in vivo

Transfer of anticonvulsants and lithium into amniotic fluid, umbilical cord blood & breast milk: A systematic review & combined analysis

OBJECTIVE

Data on the ability of anticonvulsants and lithium to enter fetal and newborn circulation has become increasingly available; here we estimated penetration ratios in a series of matrices from combined samples of pregnant/breastfeeding women treated with anticonvulsants or lithium.

METHODS

We conducted a systematic literature search in PubMed/EMBASE for studies with concentrations of anticonvulsants/lithium from maternal blood, amniotic fluid, umbilical cord blood and/or breast milk. Penetration ratios were calculated by dividing the concentrations in amniotic fluid, umbilical cord plasma or breast milk by the maternal concentrations. When data from multiple studies were available, we calculated combined penetration ratios, weighting studies' mean by study size.

RESULTS

Ninety-one eligible studies for brivaracetam, carbamazepine, clonazepam, ethosuximide, gabapentin, lacosamide, lamotrigine, levetiracetam, lithium, oxcarbazepine, perampanel, phenobarbital, phenytoin, pregabalin, primidone, topiramate, valproate, vigabatrin and zonisamide were identified. For amniotic fluid, the highest penetration ratios were estimated for levetiracetam (mean 3.56, range 1.27-5.85, n = 2) and lowest for valproate (mean 0.11, range 0.02-1.02, n = 57). For umbilical cord plasma, oxcarbazepine had the highest ratio (mean 1.59, range 0.11-4.33, n = 12) with clonazepam having the lowest (mean 0.55, range 0.52-0.59, n = 2). For breast milk, the highest ratios were observed for oxcarbazepine (mean 3.75, range 0.5-7.0, n = 2), whereas the lowest were observed for valproate (mean 0.04, range 0.01-0.22, n = 121).

DISCUSSION

We observed substantial variability between anticonvulsants and lithium regarding their ability to enter fetal/newborn circulation. Assessing concentrations of anticonvulsants and lithium in maternal samples can provide a surrogate of fetal/infant exposure, although patterns of concentration-dependent effects for maternal/neonatal safety are lacking.

Application of Physiologically Based Pharmacokinetic Modeling to Predict Maternal Pharmacokinetics and Fetal Exposure to Oxcarbazepine

Pregnancy is associated with physiological changes that may affect drug pharmacokinetics (PKs). The aim of this study was to establish a maternal-fetal physiologically based pharmacokinetic (PBPK) model of oxcarbazepine (OXC) and its active metabolite, 10,11-dihydro-10-hydroxy-carbazepine (MHD), to (1) assess differences in pregnancy, (2) predict changes in PK target parameters of these molecules following the current dosing regimen, (3) assess predicted concentrations of these molecules in the umbilical vein at delivery, and (4) compare different methods for estimating drug placental penetration. Predictions using the pregnancy PBPK model of OXC resulted in maternal concentrations within a 2-fold error, and extrapolation of the model to early-stage pregnancies indicated that changes in median PK parameters remained above target thresholds, requiring increased frequency of monitoring. The dosing simulation results suggested dose adjustment in the last two trimesters. We generally recommend that women administer ≥ 1.5× their baseline dose of OXC during their second and third trimesters. Test methods for predicting placental transfer showed varying performance, with the in vitro method showing the highest predictive accuracy. Exposure to MHD in maternal and fetal venous blood was similar. Overall, the above-mentioned models can enhance understanding of the maternal-fetal PK behavior of drugs, ultimately informing drug-treatment decisions for pregnant women and their fetuses.

Predicting Human Fetal Drug Exposure Through Maternal-Fetal PBPK Modeling and In Vitro or Ex Vivo Studies

Medication (drug) use in human pregnancy is prevalent. Determining fetal safety and efficacy of drugs is logistically challenging. However, predicting (not measuring) fetal drug exposure (systemic and tissue) throughout pregnancy is possible through maternal-fetal physiologically based pharmacokinetic (PBPK) modeling and simulation. Such prediction can inform fetal drug safety and efficacy. Fetal drug exposure can be quantified in 2 complementary ways. First, the ratio of the steady-state unbound plasma concentration in the fetal plasma (or area under the plasma concentration-time curve) to the corresponding maternal plasma concentration (ie, Kp,uu ). Second, the maximum unbound peak (Cu,max,ss,f ) and trough (Cu,min,ss,f ) fetal steady-state plasma concentrations. We (and others) have developed a maternal-fetal PBPK model that can successfully predict maternal drug exposure. To predict fetal drug exposure, the model needs to be populated with drug specific parameters, of which transplacental clearances (active and/or passive) and placental/fetal metabolism of the drug are critical. Herein, we describe in vitro studies in cells/tissue fractions or the perfused human placenta that can be used to determine these drug-specific parameters. In addition, we provide examples whereby this approach has successfully predicted systemic fetal exposure to drugs that passively or actively cross the placenta. Apart from maternal-fetal PBPK models, animal studies also have the potential to estimate fetal drug exposure by allometric scaling. Whether such scaling will be successful is yet to be determined. Here, we review the above approaches to predict fetal drug exposure, outline gaps in our knowledge to make such predictions and map out future research directions that could fill these gaps.

The role of xenobiotic-metabolizing enzymes in the placenta: a growing research field

Introduction: The placenta is a temporary and unique organ that allows for the physical connection between a mother and fetus; this organ regulates the transport of gases and nutrients mediating the elimination of waste products contained in the fetal circulation. The placenta performs metabolic and excretion functions, on the basis of multiple enzymatic systems responsible for the oxidation, reduction, hydrolysis, and conjugation of xenobiotics. These mechanisms give the placenta a protective role that limits the fetal exposure to harmful compounds. During pregnancy, some diseases require uninterrupted treatment even if it is detrimental to the fetus. Drugs and other xenobiotics alter gene expression in the placenta with repercussions for the fetus and mother's well-being.Areas covered: This review provides a brief description of the human placental structure and function, the main drug and xenobiotic transporters and metabolizing enzymes, placenta-metabolized substrates, and alterations in gene expression that the exposure to xenobiotics may cause.Expert opinion: Research should be focused on the identification and validation of biological markers for the assessment of the harmful effects of some drugs in pregnancy, including the evaluation of polymorphisms and methylation patterns in chorionic villous samples and/or amniotic fluid.

Prenatal exposure to oxcarbazepine increases hippocampal apoptosis in rat offspring

This study assessed apoptosis in the offspring of rats exposed to oxcarbazepine (OXC) from day 7 to 15 of gestation. Three groups of pregnant Wistar rats were used: 1) Control, treated with saline solution; 2) treated with 100 mg/kg OXC; 3) treated with 100 mg/kg of carbamazepine (CBZ, as a positive control for apoptosis); the route of administration was intragastric. Apoptosis was detected at three postnatal ages using the TUNEL technique in the CA1, and CA3 regions of the hippocampus and in the dentate gyrus (DG); neurogenesis was assessed in the DG using an antibody against doublecortin. The litter characteristics were recorded. OXC increased apoptosis in all regions (p < 0.01) at the three ages evaluated. Lamination disruption occurred in CA1 and CA3 due to the neuron absence and to ectopic neurons; there were also malformations in the dorsal lamina of the DG in 38% and 25% of the pups born from rats treated with OXC and CBZ respectively. CBZ also increased apoptosis. No clear effect on neurogenesis in the DG was observed. The size of the litter was smaller (p < 0.01) in the experimental groups. Nineteen-day OXC fetuses had low weight (p < 0.01), but 21 and 30 postnatal days old CBZ and OXC pups were overweight (p < 0.01). The results demonstrate that OXC administered during gestation is pro-apoptotic, alters the cytoarchitecture of the hippocampus, reduces litter size, and probably influences postnatal weight. We provide evidence of the proapoptotic effect of CBZ when administered early in gestation.

Effect of epilepsy in pregnancy on fetal growth restriction: a systematic review and meta-analysis

PURPOSE

Epilepsy is one of the most common neurological diseases during pregnancy. However, the influence of epilepsy on fetal growth is not understood. Thus, this study conducted a meta-analysis to determine the influence of epilepsy during pregnancy on fetal growth restriction (FGR).

METHODS

BIOSIS, Medline, Embase, and PubMed databases were searched between January 2000 and January 2016. Without imposing language or regional restrictions, referenced articles were selected.

RESULTS

Final analysis included 684 citations from 11 studies. Estimated risk of FGR was 1.28-fold higher in epileptic pregnant women than in non-epileptic women [95% confidence interval (95% CI) 1.09-1.50, p < 0.05]. Given the course of previous studies, hierarchical analysis of pregnant women who use antiepileptic drugs (AEDs) was conducted. Results show that FGR rate is significantly increased even if AEDs were taken [odds ratio 1.26, 95% CI 1.13-1.41, p < 0.05].

CONCLUSIONS

Although modest bias cannot be avoided, our meta-analysis indicated that epilepsy participates in fetal development as an unfavorable factor, and AEDs seemed to be useless in decreasing the occurrence rate of FGR.

Placental passage of antiepileptic drugs at delivery and neonatal outcomes

Children of women treated with antiepileptic drugs (AEDs) are at increased risk of adverse outcomes detectable in the neonatal period, which may be associated with the amount of AEDs in the fetal circulation. Placental passage of AEDs can be measured by calculating the ratio of umbilical cord to maternal AED concentrations collected at delivery. The aims of this study were to determine the umbilical cord concentrations and umbilical-to-maternal ratios for AEDs, and whether higher cord concentrations are associated with increased risk of neonatal complications. AED cord and maternal blood concentrations from 70 mother-newborn dyads and neonatal complications were recorded. Logistic regressions were performed to determine the association between AED concentrations and complications. Mean umbilical-to-maternal ratios for total concentrations ranged from 0.79 for carbamazepine to 1.20 for valproic acid, and mean umbilical-to-maternal ratios for free concentrations ranged from 0.86 for valproic acid to 1.42 for carbamazepine, indicating complete placental passage. Neither umbilical cord concentrations nor umbilical-to-maternal ratios were associated with adverse neonatal outcomes. Additional investigations are warranted to delineate the relationship between quantified fetal AED exposure and neonatal complications.

SCN8A Epileptic Encephalopathy: Detection of Fetal Seizures Guides Multidisciplinary Approach to Diagnosis and Treatment

BACKGROUND

SCN8A mutations are rare and cause a phenotypically heterogeneous early onset epilepsy known as early infantile epileptic encephalopathy type 13 (EIEE13, OMIM #614558). There are currently no clear genotype-phenotype correlations to help guide patient counseling and management.

PATIENT DESCRIPTION

We describe a patient with EIEE13 (de novo heterozygous pathogenic mutation in SCN8A - p.Ile240Val (ATT>GTT)) who presented prenatally with maternally reported intermittent, rhythmic movements that, when observed on ultrasound, were concerning for fetal seizures. Ultrasound also revealed abnormal developmental states. With maternal administration of levetiracetam, the rhythmic fetal movements stopped. After birth, the patient developed treatment-refractory multi-focal epilepsy confirmed by electroencephalogram. Neuroimaging revealed restricted diffusion in the superior cerebellar peduncles, a finding not reported previously in EIEE13.

CONCLUSION

This is the first report of EIEE13 associated with clinical prenatal-onset seizures. Ultrasonography can be useful for identifying fetal seizures, which may be treatable in utero. Ideally, the clinical approach to fetal seizures should involve a multidisciplinary team spanning the pre- and postnatal course to expedite early diagnosis and optimize management, as illustrated by this patient.

Oxcarbazepine-loaded polymeric nanoparticles: development and permeability studies across in vitro models of the blood-brain barrier and human placental trophoblast

Encapsulation of antiepileptic drugs (AEDs) into nanoparticles may offer promise for treating pregnant women with epilepsy by improving brain delivery and limiting the transplacental permeability of AEDs to avoid fetal exposure and its consequent undesirable adverse effects. Oxcarbazepine-loaded nanoparticles were prepared by a modified solvent displacement method from biocompatible polymers (poly(lactic-co-glycolic acid) [PLGA] with or without surfactant and PEGylated PLGA [Resomer^® RGPd5055]). The physical properties of the developed nanoparticles were determined with subsequent evaluation of their permeability across in vitro models of the blood–brain barrier (hCMEC/D3 cells) and human placental trophoblast cells (BeWo b30 cells). Oxcarbazepine-loaded nanoparticles with encapsulation efficiency above 69% were prepared with sizes ranging from 140–170 nm, polydispersity indices below 0.3, and zeta potential values below -34 mV. Differential scanning calorimetry and X-ray diffraction studies confirmed the amorphous state of the nanoencapsulated drug. The apparent permeability (P_e) values of the free and nanoencapsulated oxcarbazepine were comparable across both cell types, likely due to rapid drug release kinetics. Transport studies using fluorescently-labeled nanoparticles (loaded with coumarin-6) demonstrated increased permeability of surfactant-coated nanoparticles. Future developments in enzyme-prodrug therapy and targeted delivery are expected to provide improved options for pregnant patients with epilepsy.

Effects of Levetiracetam on neural tube development and closure of the chick embryos in ovo

PURPOSE

Effects of Levetiracetam (LEV) within its therapeutic range at a 50 mg/kg dose for the chick embryo in ovo has been studied in order to demonstrate whether LEV would effect neural tube closure at the macroscopic morphology or LEV administered embryos still encounter neuroglial detrimental effects at the histological level.

METHODS

Embryos were randomly seperated into control (n = 20) and study (n = 20) groups. The eggshell was windowed at specifically 24 h of incubation, and area underlying the membrane was excised to allow injection with 4.5 μl LEV in the study group, while physiologic saline (0.045 ml) were injected in the control group and each egg were re-incubated for 48 h more. Then, histological and immunohistochemical evaluation of the subjects were done.

RESULTS

Macroscopic evaluation revealed immaturity of the placental vessel network in number and width for the study group in comparison to the controls. Defects of migration, decrease in the crista neuralis content, delay of the basal plates structures in the formation of the usual configuration, and delay in the cellular proliferation and the delay of development for the central nervous system were determined in the LEV-exposed group. Immunostaining of S100 proteins in this study has clearly demonstrated increased expression patterns of both neuroglial and neuronal cell populations. Toluidine blue stainings revealed mostly bipolar, differentiating neurons and crista neuralis cells which is concordant with active migration and differentiation.

CONCLUSIONS

LEV found that delay in the closure of the neural tube and microcephalic fetuses disturb further morphological, biochemical, and functional development.

Patient knowledge about issues related to pregnancy in epilepsy: a cross-sectional study

In 2009, new guidelines were established by the American Academy of Neurology regarding pregnancy in women with epilepsy. A questionnaire was developed to assess patient knowledge of current guidelines related to epilepsy and pregnancy. Patients were recruited from a single outpatient clinic in a large Canadian tertiary care center. Patients were eligible to participate if they were female, of reproductive age, had active epilepsy for at least 6 months and were not cognitively impaired. One hundred women completed the survey (response rate 87%) with a median score of 40%. A significant association was found between total score and years of education (p<0.001). Significant associations were not found between total score and epilepsy duration (p=0.37), previously being pregnant (p=0.22), and polytherapy (p=0.31). Patient knowledge of the impact of epilepsy on pregnancy is low. More knowledge translation efforts are required to increase knowledge of issues related to pregnancy for women with epilepsy.

Practice parameter update: management issues for women with epilepsy--focus on pregnancy (an evidence-based review): vitamin K, folic acid, blood levels, and breastfeeding: report of the Quality Standards Subcommittee and Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology and American Epilepsy Society

OBJECTIVE

To reassess the evidence for management issues related to the care of women with epilepsy (WWE) during pregnancy, including preconceptional folic acid use, prenatal vitamin K use, risk of hemorrhagic disease of the newborn, clinical implications of placental and breast milk transfer of antiepileptic drugs (AEDs), risks of breastfeeding, and change in AED levels during pregnancy.

METHODS

A 20-member committee evaluated the available evidence based on a structured literature review and classification of relevant articles published between 1985 and October 2007.

RESULTS

Preconceptional folic acid supplementation is possibly effective in preventing major congenital malformations in the newborns of WWE taking AEDs. There is inadequate evidence to determine if the newborns of WWE taking AEDs have a substantially increased risk of hemorrhagic complications. Primidone and levetiracetam probably transfer into breast milk in amounts that may be clinically important. Valproate, phenobarbital, phenytoin, and carbamazepine probably are not transferred into breast milk in clinically important amounts. Pregnancy probably causes an increase in the clearance and a decrease in the concentration of lamotrigine, phenytoin, and to a lesser extent carbamazepine, and possibly decreases the level of levetiracetam and the active oxcarbazepine metabolite, the monohydroxy derivative.

RECOMMENDATIONS

Supplementing women with epilepsy with at least 0.4 mg of folic acid before they become pregnant may be considered (Level C). Monitoring of lamotrigine, carbamazepine, and phenytoin levels during pregnancy should be considered (Level B) and monitoring of levetiracetam and oxcarbazepine (as monohydroxy derivative) levels may be considered (Level C). A paucity of evidence limited the strength of many recommendations.

Antiepileptic drug therapy in pregnancy II: fetal and neonatal exposure

The issue of how much an antiepileptic drug (AED) crosses the placenta and relative safety of lactation in mothers receiving AEDs are common clinical questions. Educating potential mothers with epilepsy regarding available information is warranted so that informed decisions and any needed neonatal monitoring is performed. Unfortunately, there is still limited data regarding the degree in which anticonvulsants cross the placenta and penetrate into breast milk. There is a greater appreciation of the factors that influence AED passive transfer across the placenta and into breast milk, as well as factors that ultimately influence neonatal AED distribution. In general, women with epilepsy can have healthy babies even with significant placental exposure and can breast-feed their babies safely with some cautions. Phenobarbital and primidone should be avoided in parents wishing to breast-feed. For the AEDs ethosuximide, levetiracetam, lamotrigine, topiramate, and zonisamide, there is a potential for significant breast milk concentrations; however, there are no firm guidelines on whether lactation is safe. In all cases, parents should be counseled to monitor their child for side effects and the need for routine monitoring.

The fate and effects of xenobiotics in human placenta

During past decades, knowledge on placental drug metabolism and mechanisms of placental transfer has increased significantly. Most pharmaceutical drugs administered during pregnancy cross the placenta to some extent. The important properties determining the placental transfer by passive diffusion are molecular weight, pK(a), lipid solubility and protein binding. In addition to passive diffusion, compounds may cross the placenta via active transfer, facilitated diffusion, phagocytosis and pinocytosis. This review gives an update of efflux transporter proteins and xenobiotic-metabolizing enzymes that modify the fate and effects of drugs in the placenta.

Neuroteratogens in man: An overview with special emphasis on the teratogenicity of antiepileptic drugs in pregnancy

The most active growth and development of the human cerebrum and cerebellum occurs in the second half of pregnancy and in the first year of life. It is therefore not surprising that many teratogens may also affect development causing slight, moderate or even severe brain damage. The "classical" antiepileptic drugs (AEDs) valproic acid (VPA), phenytoin, phenobarbital, primidone and carbamazepine are all considered to be teratogenic. They may increase the rate of major congenital anomalies including neural tube defects (NTD), cause specific facial and other dysmorphic features--the "Anti Epileptic Drug Syndrome" (AEDS) and often some degree of mental impairment. Of these AEDs, the most teratogenic seems to be valproic acid, causing about 2% of NTD and an additional increase of 4-8% in major congenital anomalies. Phenytoin also increases the rate of various anomalies, but apparently not of NTD. Phenobarbital primidone and carbamazepine are also teratogenic and impair intellectual function but to a lesser extent than VPA and phenytoin. Cognition is mainly impaired in the children that also exhibit the AEDS. The impairment is slight to moderate, leaving the affected children with a close to borderline intelligence. Lamotrigine monotherapy in pregnancy seems to be relatively safe. In general, polytherapy is more dangerous to the fetus than monotherapy and, at least for VPA and lamotrigine, there seems to be a "threshold effect".

Prophylactic treatment of bipolar disorder in pregnancy and breastfeeding: focus on emerging mood stabilizers

OBJECTIVES

Bipolar disorders are reported to have a high incidence during childbearing years and the need may arise to start or continue a pharmacological treatment during pregnancy and the postpartum period. In the last few years several investigations have evaluated the efficacy of emerging mood-stabilizing agents in the treatment of bipolar disorders, such as lamotrigine, olanzapine, risperidone, quetiapine, aripiprazole and ziprasidone. A number of studies, which examined the use of oxcarbazepine, point to its potential usefulness in prophylactic treatment. The aim of this review is to compare information from the literature on the safety of lamotrigine, oxcarbazepine, risperidone, olanzapine, and quetiapine to the safety data on classic mood stabilizers during pregnancy and the postpartum period.

METHODS

A computerized search carried out from 1980 to April 5, 2006 led to the summarization of the results. (References were updated after acceptance and prior to publication.)

RESULTS

Emerging mood stabilizers show uncertain safety parameters in pregnancy and lactation. Limited information on lamotrigine and oxcarbazepine does not suggest a clear increase in teratogenicity, while olanzapine appears to be associated with a higher risk of metabolic complications in pregnant women. Data about risperidone and quetiapine are still inconclusive. Finally, the literature on the safety of these compounds in breastfeeding is anecdotal.

CONCLUSIONS

Untreated pregnant bipolar women are at an increased risk of poor obstetrical outcomes and relapse of affective symptoms. On the other hand, classic antiepileptic drugs are well-known human teratogens, whereas data on lithium are partially ambiguous. The safety of emerging mood stabilizers in pregnancy and breastfeeding has not been examined extensively. Therefore, when approaching bipolar disorder, if possible, each episode must be considered separately.

Gender Aspects of Pharmacokinetics of New and Old AEDs

Alterations in drug disposition in pregnancy and drug transfer into breast milk during lactation are the most important gender-related aspects of the pharmacokinetics of antiepileptic drugs(AEDs). The effect of pregnancy on drug disposition has been fairly well characterized for the old AEDs. Total and unbound plasma concentrations of phenobarbital decline up to 50%. Total phenytoin levels may drop to approximately 40% of prepregnancy concentrations,but unbound concentrations considerably less. Unbound valproate levels remain unchanged despite a fairly marked decrease in total concentrations, and changes in unbound and total plasma concentrations of carbamazepine are minor. In contrast, pregnancy has a pronounced effect on lamotrigine, with a 300% increase in apparent clearance in the third trimester. Much less is known about the kinetics of other new AEDs during pregnancy. Umbilical cord/maternal plasma concentration ratios close to unity suggest free transplacental passage of most AEDs,whereas higher ratios indicate fetal accumulation of valproate and gabapentin. Milk/maternal plasma concentration ratios close to 1 demonstrate extensive transfer to breast milk of many AEDs including ethosuximide, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, topiramate, and zonisamide. Plasma levels are, however, in general low in the nursed infant, although pharmacological concentrations have been reported occasionally for carbamazepine, ethosuximide, lamotrigine, and phenobarbital. For most of the new-generation AEDs, there is an urgent need for further kinetic data from pregnancy and breast-feeding.

Psychotropic drugs in pregnancy and lactation

The management of psychotropic medications during pregnancy and lactation involves a difficult and complex decision for both patient and provider, particularly due to the many unknown effects medication may have on the infant. Available studies concerning use of psychotropic medications in pregnant and lactating women are limited and there are no universal guidelines. This article reviews the literature on the use of psychotropic drugs, including antidepressants, mood stabilizers, antipsychotics, and benzodiazepines, in pregnant and breast-feeding women and presents relevant data on teratogenic effects, neonatal toxicity, perinatal syndromes, and neurobehavioral sequelae.

Safety of the newer antiepileptic drug oxcarbazepine during pregnancy

OBJECTIVE

Seizure control in pregnant women with epilepsy is vital, as maternal seizures may have deleterious consequences. The treatment of pregnant women with epilepsy is, however, complicated by the teratogenicity of older antiepileptic drugs (AEDs). In this review, the safety of the newer AED oxcarbazepine during pregnancy is assessed based on published pregnancy outcome data. Other relevant safety issues, such as oxcarbazepine pharmacokinetics during pregnancy and the compatibility of oxcarbazepine treatment with breastfeeding, are also discussed.

METHODS

Literature searches of the following databases were performed: MEDLINE, EMBASE, eNova, NOWIMA (an internal Novartis Germany database), Derwent Drug File, SciSearch and BIOSIS. Identified publications were examined for original data reporting rates of foetal malformation following maternal exposure to oxcarbazepine as monotherapy or adjunctive therapy.

RESULTS

Relevant publications reporting data from the worldwide Novartis safety database and pregnancy registries or study centres in six countries were identified. A total of 248 pregnancies involving maternal exposure to oxcarbazepine monotherapy and 61 involving adjunctive therapy were reported. There were six malformations among the monotherapy group, equating to a malformation rate of 2.4% (6/248). The malformation rate reported in the general population is 2-4%. There were four malformations associated with oxcarbazepine adjunctive therapy, equating to a malformation rate of 6.6% (4/61).

CONCLUSIONS

This literature review suggests that, compared with newborns in the general population, the newborns of women receiving oxcarbazepine monotherapy during pregnancy do not appear to show an increased risk for malformations. However, the number of pregnancies involving maternal exposure to oxcarbazepine identified by this review is not sufficient to draw definitive conclusions. Additional information from large-scale pregnancy registries is required to confirm the safety profile of oxcarbazepine as monotherapy or adjunctive therapy during pregnancy.

Clinical pharmacokinetics of oxcarbazepine

Oxcarbazepine is an antiepileptic drug with a chemical structure similar to carbamazepine, but with different metabolism. Oxcarbazepine is rapidly reduced to 10,11-dihydro-10-hydroxy-carbazepine (monohydroxy derivative, MHD), the clinically relevant metabolite of oxcarbazepine. MHD has (S)-(+)- and the (R)-(-)-enantiomer, but the pharmacokinetics of the racemate are usually reported. The bioavailability of the oral formulation of oxcarbazepine is high (>95%). It is rapidly absorbed after oral administration, reaching peak concentrations within about 1-3 hours after a single dose, whereas the peak of MHD occurs within 4-12 hours. At steady state, the peak of MHD occurs about 2-4 hours after drug intake. The plasma protein binding of MHD is about 40%. Cerebrospinal fluid concentrations of MHD are in the same range as unbound plasma concentrations of MHD. Oxcarbazepine can be transferred significantly through the placenta in humans. Oxcarbazepine and MHD exhibit linear pharmaco-kinetics and no autoinduction occurs. Elimination half-lives in healthy volunteers are 1-5 hours for oxcarbazepine and 7-20 hours for MHD. Longer and shorter elimination half-lives have been reported in elderly volunteers and children, respectively. Mild to moderate hepatic impairment does not appear to affect MHD pharmacokinetics. Renal impairment affects the pharmacokinetics of oxcarbazepine and MHD. The interaction potential of oxcarbazepine is relatively low. However, enzyme-inducing antiepileptic drugs such as phenytoin, phenobarbital or carbamazepine can reduce slightly the concentrations of MHD. Verapamil may moderately decrease MHD concentrations, but this effect is probably without clinical relevance. The influence of oxcarbazepine on other antiepileptic drugs is not clinically relevant in most cases. However, oxcarbazepine appears to increase concentrations of phenytoin and to decrease trough concentrations of lamotrigine and topiramate. Oxcarbazepine lowers concentrations of ethinylestra-diol and levonorgestrel, and women treated with oxcarbazepine should consider additional contraceptive measures. Due to the absent or lower enzyme-inducing effect of oxcarbazepine, switching from carbamazepine to oxcarbazepine can result in increased serum concentrations of comedication, sometimes associated with adverse effects. The effect of oxcarbazepine appears to be related to dose and to serum concentrations of MHD. In general, daily fluctuations of MHD concentration are relatively slight, smaller than would be expected from the elimination half-life of MHD. However, relatively high fluctuations can be observed in individual patients. Therapeutic monitoring may help to decide whether adverse effects are dependent on MHD concentrations. A mean therapeutic range of 15-35 mg/L for MHD seems to be appropriate. However, more systematic studies exploring the concentration-effect relationship are required.

Reproductive and metabolic disorders in women with epilepsy

Epilepsy is a common neurologic disorder affecting women during the reproductive years. Seizures and some antiepileptic drugs (AEDs) can compromise reproductive health, and some AEDs can adversely affect carbohydrate and bone metabolism. Women with epilepsy have lower birth rates and more frequent anovulatory menstrual cycles. This appears to be related to seizure- and AED-associated reproductive endocrine disturbances. Carbamazepine (CBZ), phenytoin (PHT), and phenobarbital (PB) induce hepatic cytochrome P450 enzymes and lower endogenous estrogens, adrenal and ovarian androgens, and contraceptive steroids. Valproate (VPA) inhibits steroid hormone metabolism, elevates androgens, and predisposes to phenotypic signs of hyperandrogenism-hirsutism, obesity, acne, and frequent anovulatory cycles. VPA is associated with weight gain, probably by altering insulin metabolism. CBZ, PHT, and VPA, but not lamotrigine (LTG), are associated with lower levels of calcium. PHT, but not VPA or LTG, appears to accelerate bone turnover. AED effects on bone mineral metabolism may explain the elevated risk of fracture described in women with epilepsy. Prospective pregnancy registries are beginning to provide information about AED-associated teratogenesis. The North American Antiepileptic Drug Pregnancy Registry reports a 12% rate of major malformations after first trimester exposure to PB and an 8.6% rate after first trimester exposure to VPA. A prospective LTG-specific registry reports a 1.8% chance of major malformations after the first trimester. The registries will continue to release information as data become significant. In the meantime, practitioners can be alert to signs and symptoms of reproductive or metabolic health disturbances and participate in pregnancy registry efforts.

Transplacental passage of lamotrigine in a human placental perfusion system in vitro and in maternal and cord blood in vivo

OBJECTIVE

We studied transplacental passage of lamotrigine (3,5-diamino-6-[2,3-dichlorophenyl]-1,2,4-triazine; LTG) using an ex vivo human placental perfusion method and in in vivo samples.

METHODS

Term placentas from healthy mothers without medications were perfused in a recirculating dual perfusion system. LTG (2.5 microg/ml, n=4; 10 microg/ml, n=4) and reference compound antipyrine (100 microg/ml) were added into the maternal circulation. The disappearance of drugs from the maternal circulation and appearance into the foetal circulation was followed every 15 min up to 2 h. Drug concentrations were analysed using high-performance liquid chromatography. In addition to human placental perfusions, we analysed LTG concentrations in maternal vein and cord blood samples after delivery from two epileptic mothers receiving LTG therapy during pregnancy.

RESULTS

LTG was detectable in the foetal circulation at 15 min in all of the perfusions, indicating rapid transfer. Maternal and foetal concentrations reached equilibrium at 60 min with both concentrations used. The feto-maternal ratio was 1.26+/-0.20 with 10 microg/ml LTG and 0.83+/-0.41 with 2.5 microg/ml LTG at the end of the perfusion. The transfer of LTG from the maternal to the foetal compartment at 120 min was 28.9+/-10.7% with 2.5 microg/ml LTG and 37.8+/-3.2% with 10 microg/ml LTG (p>0.05). In the serum samples from epileptic mothers, the cord blood maternal concentration ratio was 1.02 in one pair and 1.55 in the other.

CONCLUSIONS

LTG crossed the placenta easily and rapidly, indicating that the maternal treatment leads to a considerable foetal exposure.

Fetal heart rate decelerations during ECT-induced seizures: is it important?

Electroconvulsive therapy (ECT) is sometimes indicated during pregnancy and may offer advantages over pharmacotherapy for the patient and the fetus (1,2). However, very little data is available on the impact of epileptic or ECT-induced seizures on the fetus. We report a case of brief fetal heart rate decelerations in a fetus associated with maternal ECT-induced convulsions.

An examination of whether human placental perfusion allows accurate prediction of placental drug transport: Studies with diazepam

INTRODUCTION

Presently, no well-validated predictive tools are available for human placental transfer. We studied the transplacental passage of diazepam (DZP) in a recirculating dual human placental perfusion and compared the data with in vivo clinical data from the literature.

METHODS

Term placentas from healthy mothers without medication were used. The dual, recirculating perfusion technique was used. DZP (2 microg/ml, n = 4; 200 ng/ml, n = 3) and the reference compound antipyrine (100 microg/ml) were added into the maternal circulation simultaneously. The disappearance of drugs from the maternal circulation and appearance into the fetal circulation were followed every 15 min for 2 h.

RESULTS

DZP was detectable in the fetal circulation within 15 min in all of the perfusions indicating rapid transfer. DZP concentrations in the maternal circulation were higher than in the fetal circulation throughout the perfusion with both initial concentrations. At the end of the perfusion, the feto-maternal ratio was 0.48 +/- 0.11 (mean +/- S.D.) and the transfer from the maternal to the fetal compartment 18.4 +/- 3.6% with 2 microg/ml of DZP and 0.55 +/- 0.10 and 20.5 +/- 3.1% with 200 ng/ml of DZP, respectively. DZP concentrations in the perfused area of the placenta were in average 2 times higher than in the maternal perfusate and 3.6 times higher than in the fetal perfusate. Total recovery of DZP from samples, perfusion fluid, and perfused tissue was 37.6 +/- 21%.

DISCUSSION

Since animal studies in vivo do not accurately predict human placental transfer and it is problematic to study placental transfer of drugs in humans in vivo, the present human placental perfusion system could serve as one part of a test battery for fetotoxicity. However, although our earlier studies and those from the literature indicate a good correlation between in vivo and placental perfusion data, the present study shows this is not the case for all drugs.