Changes in the disposition of oxcarbazepine and its metabolites during pregnancy and the puerperium

From barbiturates to ganaxolone: The importance of chirality in drug development and in understanding the actions of old and new antiseizure medications

Out of 37 antiseizure medications (ASMs) currently in the market, 17 are chiral molecules and an additional one (oxcarbazepine) is a prodrug of the chiral compound licarbazepine. Of the 17 chiral ASMs, six (ethosuximide, fenfluramine, methsuximide, mephobarbital, stiripentol and vigabatrin) are marketed as racemates, and the remainder are licensed as enantiomerically pure medicines. Of note, all chiral ASMs introduced prior to 1990 were marketed as racemates. Stiripentol, fenfluramine and vigabatrin are the only racemic ASMs approved by the FDA >10 years after the release of regulatory guidelines on the development of chiral medicines. Despite the fact that pharmacokinetic and pharmacodynamic differences between enantiomers have been recognized for decades, the importance of chirality in understanding the biological actions of ASMs is not widely appreciated, and many recent publications on racemic ASMs refer to these medications as if they were a single molecular entity. In the present article, we provide a critical review of chiral ASMs developed between the 1920s, when mephobarbital was introduced, and 2022, when the last chiral ASM (ganaxolone) was approved. We summarize available data on stereoselective differences in pharmacokinetics and pharmacodynamics of ASMs marketed as racemates. We also discuss regulatory aspects related to the introduction of racemic medicines within the current regulatory scenario in Europe and the U.S., focusing on stiripentol, vigabatrin and fenfluramine as examples of different approaches. We identified a number of critical knowledge gaps that are relevant to the use of chiral drugs in epilepsy, including a remarkable lack of published information on the comparative pharmacokinetics, toxicity and antiseizure activity of the enantiomers of most racemic ASMs. The importance of chirality aspects in understanding the clinical actions of racemic ASMs is discussed, together with the rationale for the development of enantiomerically pure follow-up compounds with potentially improved efficacy, safety and commercial viability.

The impact of pregnancy-related hormonal and physiological changes on antiseizure medications: expert perspective

INTRODUCTION

Epilepsy is a disorder of recurrent, unprovoked seizures affecting approximately 15 million individuals of childbearing potential worldwide. Patients with epilepsy rely on regular daily therapy with antiseizure medications (ASMs). Furthermore, ASMs are also prescribed for other neuropsychiatric indications (e.g. bipolar disorder, pain, migraines) with over 2% of the pregnancies in the United States involving prenatal exposure to ASMs.

AREAS COVERED

ASM concentrations are affected by hormonal and physiological changes in pregnancy, including increases in renal and hepatic blood flow, decreased protein binding, and changes in enzyme activity. Clearance changes typically reverse within a few weeks after delivery. During pregnancy, many ASMs, such as lamotrigine, levetiracetam, and oxcarbazepine, should have serum concentrations monitored and doses increased to maintain the individualized target range for seizure control. ASMs metabolized via glucuronidation, primarily lamotrigine, undergo marked increases in clearance throughout pregnancy, requiring about 3-fold the pre-pregnancy daily dose by delivery. Postpartum, ASM doses are usually decreased over several weeks to prevent drug toxicity.

EXPERT OPINION

In the future, the development of a physiologically-based pharmacokinetic model for various ASMs may enable empiric dose adjustments in pregnancy without the difficulties of frequent therapeutic drug monitoring.

Association of oxcarbazepine concentration with seizure frequency in pregnant women with epilepsy

The management of epilepsy during pregnancy presents particular challenges for neurologists worldwide. Currently, there are no clear recommendations for oxcarbazepine (OXC) specific target concentration during pregnancy. We conducted this retrospective observational cohort study on pregnant women with epilepsy (WWE) who received OXC monotherapy or polytherapy, at the epilepsy outpatient clinic of a tertiary hospital in eastern China. Sixteen pregnancies of 16 WWE were split into the seizure-free group or the non-seizure-free group, according to whether they had been seizure free for more than one year prior to conception or not. There was a significantly decrease in OXC concentration throughout pregnancy, as indicated by the concentration/dose ratio and the ratio of target concentration (RTC). The second trimester of pregnancy was the period when seizure deterioration occurred the most, particularly in the non-seizure-free group. Lower RTC_OXC was identified to be a risk factor for increasing seizure frequency in both the total group and the non-seizure-free group in both univariate and multivariate analysis, with a threshold of 0.575 for differentiating patients at high-risk and low-risk for seizure deterioration. In conclusion, this study suggested an OXC concentration threshold of 0.575 during pregnancy for assisting neurologists in OXC drug monitoring and dose adaptation.

Management of Anti-Seizure Medications during Pregnancy: Advancements in The Past Decade

Management of seizures often involves continuous medication use throughout a patient's life, including when a patient is pregnant. The physiological changes during pregnancy can lead to altered drug exposure to anti-seizure medications, increasing patient response variability. In addition, subtherapeutic anti-seizure medication concentrations in the mother may increase seizure frequency, raising the risk of miscarriage and preterm labor. On the other hand, drug exposure increases can lead to differences in neurodevelopmental outcomes in the developing fetus. Established pregnancy registries provide insight into the teratogenicity potential of anti-seizure medication use. In addition, some anti-seizure medications are associated with an increased risk of major congenital malformations, and their use has declined over the last decade. Although newer anti-seizure medications are thought to have more favorable pharmacokinetics in general, they are not without risk, as they may undergo significant pharmacokinetic changes when an individual becomes pregnant. With known changes in metabolism and kidney function during pregnancy, therapeutic monitoring of drug concentrations helps to determine if and when doses should be changed to maintain similar seizure control as observed pre-pregnancy. This review concentrates on the results from research in the past decade (2010-2022) regarding risks of major congenital malformations, changes in prescribing patterns, and pharmacokinetics of the anti-seizure medications that are prescribed to pregnant patients with epilepsy.

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.

Breastfeeding recommendations for women taking anti-seizure medications

The literature regarding breastfeeding and effects of anti-seizure medication (ASM) exposure on the breastfed infant has been evolving rapidly over the last decade as new studies advance our understanding of the extent of medication exposure via breastfeeding and the long-term developmental outcomes of breastfed infants. Currently, strong evidence supports the safety of breastfeeding for women with epilepsy (WWE) taking most prescribed ASMs. In this review, we present a comprehensive overview of the data regarding ASM exposure in breastfed infants and neurodevelopmental outcomes in breastfed infants of mothers taking various ASMs. In addition, we present current breastfeeding recommendations and the reported adverse effects of various ASMs to facilitate decision making in the clinical care of WWE.

Treatment and care of women with epilepsy before, during, and after pregnancy: a practical guide

Women with epilepsy (WWE) wishing for a child represent a highly relevant subgroup of epilepsy patients. The treating epileptologist needs to delineate the epilepsy syndrome and choose the appropriate anti-seizure medication (ASM) considering the main goal of seizure freedom, teratogenic risks, changes in drug metabolism during pregnancy and postpartum, demanding for up-titration during and down-titration after pregnancy. Folic acid or vitamin K supplements and breastfeeding are also discussed in this review. Lamotrigine and levetiracetam have the lowest teratogenic potential. Data on teratogenic risks are also favorable for oxcarbazepine, whereas topiramate tends to have an unfavorable profile. Valproate needs special emphasis. It is most effective in generalized seizures but should be avoided whenever possible due to its teratogenic effects and the negative impact on neuropsychological development of in utero-exposed children. Valproate still has its justification in patients not achieving seizure freedom with other ASMs or if a woman decides to or cannot become pregnant for any reason. When valproate is the most appropriate treatment option, the patient and caregiver must be fully informed of the risks associated with its use during pregnancies. Folate supplementation is recommended to reduce the risk of major congenital malformations. However, there is insufficient information to address the optimal dose and it is unclear whether higher doses offer greater protection. There is currently no general recommendation for a peripartum vitamin K prophylaxis. During pregnancy most ASMs (e.g. lamotrigine, oxcarbazepine, and levetiracetam) need to be increased to compensate for the decline in serum levels; exceptions are valproate and carbamazepine. Postpartum, baseline levels are reached relatively fast, and down-titration is performed empirically. Many ASMs in monotherapy are (moderately) safe for breastfeeding and women should be encouraged to do so. This review provides a practically oriented overview of the complex management of WWE before, during, and after pregnancy.

Antiseizure Medication Concentrations During Pregnancy: Results From the Maternal Outcomes and Neurodevelopmental Effects of Antiepileptic Drugs (MONEAD) Study

IMPORTANCE

During pregnancy in women with epilepsy, lower blood concentrations of antiseizure medications can have adverse clinical consequences.

OBJECTIVE

To characterize pregnancy-associated concentration changes for several antiseizure medications among women with epilepsy.

DESIGN, SETTING, AND PARTICIPANTS

Enrollment in this prospective, observational cohort study, Maternal Outcomes and Neurodevelopmental Effects of Antiepileptic Drugs (MONEAD), occurred from December 19, 2012, to February 11, 2016, at 20 US sites. Enrolled cohorts included pregnant women with epilepsy and nonpregnant control participants with epilepsy. Inclusion criteria were women aged 14 to 45 years, an intelligence quotient greater than 70 points, and, for the cohort of pregnant women, a fetal gestational age younger than 20 weeks. A total of 1087 women were assessed for eligibility; 397 were excluded and 230 declined. Data were analyzed from May 1, 2014, to June 30, 2021.

EXPOSURE

Medication plasma concentrations in women taking monotherapy or in combination with noninteracting medications. The cohort of pregnant women was monitored through 9 months post partum, with similar time points for control participants.

MAIN OUTCOMES AND MEASURES

Dose-normalized concentrations were calculated as total or unbound plasma medication concentrations divided by total daily dose. Phlebotomy was performed during 4 pregnancy study visits and 3 postpartum visits for the pregnant women and 7 visits over 18 months for control participants. The primary hypothesis was to test pregnancy changes of dose-normalized concentrations from nonpregnant postpartum samples compared with those of control participants.

RESULTS

Of the 351 pregnant women and 109 control participants enrolled in MONEAD, 326 pregnant women (median [range] age, 29 [19-43] years) and 104 control participants (median [range] age, 29 [16-43] years) met eligibility criteria for this analysis. Compared with postpartum values, dose-normalized concentrations during pregnancy were decreased by up to 56.1% for lamotrigine (15.60 μg/L/mg to 6.85 μg/L/mg; P < .001), 36.8% for levetiracetam (11.33 μg/L/mg to 7.16 μg/L/mg; P < .001), 17.3% for carbamazepine (11.56 μg/L/mg to 7.97 μg/L/mg; P = .03), 32.6% for oxcarbazepine (11.55 μg/L/mg to 7.79 μg/L/mg; P < .001), 30.6% for unbound oxcarbazepine (6.15 μg/L/mg to 4.27 μg/L/mg; P < .001), 39.9% for lacosamide (26.14 μg/L/mg to 15.71 μg/L/mg; P < .001), and 29.8% for zonisamide (40.12 μg/L/mg to 28.15 μg/L/mg; P < .001). No significant changes occurred for unbound carbamazepine, carbamazepine-10,11-epoxide, and topiramate, although a decrease was observed for topiramate (29.83 μg/L/mg to 13.77 μg/L/mg; P = .18). Additionally, compared with dose-normalized concentrations from control participants, pregnancy dose-normalized median (SE) concentrations decreased significantly by week of gestational age: carbamazepine, -0.14 (0.06) μg/L/mg (P = .02); carbamazepine unbound, -0.04 (0.01) μg/L/mg (P = .01); lacosamide, -0.23 (0.07) μg/L/mg (P < .001); lamotrigine, -0.20 (0.02) μg/L/mg (P < .001); levetiracetam, -0.06 (0.03) μg/L/mg (P = .01); oxcarbazepine, -0.14 (0.04) μg/L/mg (P < .001); oxcarbazepine unbound, -0.11 (0.03) μg/L/mg (P < .001); and zonisamide, -0.53 (0.14) μg/L/mg (P < .001) except for topiramate (-0.35 [0.20] μg/L/mg per week) and carbamazepine-10,11-epoxide (0.02 [0.01] μg/L/mg).

CONCLUSIONS AND RELEVANCE

Study results suggest that therapeutic drug monitoring should begin early in pregnancy and that increasing doses of these anticonvulsants may be needed throughout the course of pregnancy.

Expert consensus of the Chinese Association for the Study of Pain on ion channel drugs for neuropathic pain

Neuropathic pain (NPP) is a kind of pain caused by disease or damage impacting the somatosensory system. Ion channel drugs are the main treatment for NPP; however, their irregular usage leads to unsatisfactory pain relief. To regulate the treatment of NPP with ion channel drugs in clinical practice, the Chinese Association for the Study of Pain organized first-line pain management experts from China to write an expert consensus as the reference for the use of ion channels drugs . Here, we reviewed the mechanism and characteristics of sodium and calcium channel drugs, and developed recommendations for the therapeutic principles and clinical practice for carbamazepine, oxcarbazepine, lidocaine, bulleyaconitine A, pregabalin, and gabapentin. We hope this guideline provides guidance to clinicians and patients on the use of ion channel drugs for the management of NPP.

Quantitation of Oxcarbazepine Clinically in Plasma Using Surfaced-Enhanced Raman Spectroscopy (SERS) Coupled with Chemometrics

Nondestructive, sensitive, near-real-time quantitative analysis approaches are gaining popularity and attention, especially in clinical diagnosis and detection. There is a need to propose an alternative scheme using surface-enhanced Raman spectroscopy (SERS) assisted by chemometrics to improve some defects existing using other analytical instruments to meet clinical demands. In this study, clinical drug oxcarbazepine (OXC) in human blood plasma has been quantified and detected using this method. Partial least squares regression (PLSR) modeling was employed to assess the relationship between full SERS spectral data and OXC concentration. The calibration set's correlation coefficient of the model is > 0.9, the result suggests that this method is favorable and feasible. Furthermore, other multivariate calibration algorithms like Monte Carlo cross-validation (MCCV) sample set partitioning based on joint XY distances (SPXY), adaptive iteratively reweighted penalized least squares (AIR-PLS), moving window partial least squares regression (MWPLS), and leave-one-out cross-validation were used to handle these spectral data to obtain an accurate predictive model. The results achieved in this study provide a possibility and availability for us to apply SERS in combination with chemometrics to diagnosis detection.

Therapeutic Drug Monitoring of Antiepileptic Drugs in Epilepsy: A 2018 Update

BACKGROUND

Antiepileptic drugs (AEDs) are the mainstay of epilepsy treatment. Since 1989, 18 new AEDs have been licensed for clinical use and there are now 27 licensed AEDs in total for the treatment of patients with epilepsy. Furthermore, several AEDs are also used for the management of other medical conditions, for example, pain and bipolar disorder. This has led to an increasingly widespread application of therapeutic drug monitoring (TDM) of AEDs, making AEDs among the most common medications for which TDM is performed. The aim of this review is to provide an overview of the indications for AED TDM, to provide key information for each individual AED in terms of the drug's prescribing indications, key pharmacokinetic characteristics, associated drug-drug pharmacokinetic interactions, and the value and the intricacies of TDM for each AED. The concept of the reference range is discussed as well as practical issues such as choice of sample types (total versus free concentrations in blood versus saliva) and sample collection and processing.

METHODS

The present review is based on published articles and searches in PubMed and Google Scholar, last searched in March 2018, in addition to references from relevant articles.

RESULTS

In total, 171 relevant references were identified and used to prepare this review.

CONCLUSIONS

TDM provides a pragmatic approach to epilepsy care, in that bespoke dose adjustments are undertaken based on drug concentrations so as to optimize clinical outcome. For the older first-generation AEDs (carbamazepine, ethosuximide, phenobarbital, phenytoin, primidone, and valproic acid), much data have accumulated in this regard. However, this is occurring increasingly for the new AEDs (brivaracetam, eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, perampanel, piracetam, pregabalin, rufinamide, stiripentol, sulthiame, tiagabine, topiramate, vigabatrin, and zonisamide).

Antiepileptic drug clearances during pregnancy and clinical implications for women with epilepsy

OBJECTIVE

To characterize the magnitude and time course of pregnancy-related clearance changes for different antiepileptic drugs (AEDs): levetiracetam, oxcarbazepine, topiramate, phenytoin, and valproate. A secondary aim was to determine if a decreased AED serum concentration was associated with increased seizure frequency.

METHODS

Women with epilepsy were enrolled preconception or early in pregnancy and prospectively followed throughout pregnancy and the first postpartum year with daily diaries of AED doses, adherence, and seizures. Study visits with AED concentration measurements occurred every 1-3 months. AED clearances in each trimester were compared to nonpregnant baseline using a mixed linear regression model, with adjustments for age, race, and hours postdose. In women on monotherapy, 2-sample t test was used to compare the ratio to target concentrations (RTC) between women with seizure worsening each trimester and those without.

RESULTS

AED clearances were calculated for levetiracetam (n = 18 pregnancies), oxcarbazepine (n = 4), topiramate (n = 10), valproate (n = 5), and phenytoin (n = 7). Mean maximal clearances were reached for (1) levetiracetam in first trimester (1.71-fold baseline clearance) (p = 0.0001), (2) oxcarbazepine in second trimester (1.63-fold) (p = 0.0001), and (3) topiramate in second trimester (1.39-fold) (p = 0.025). In 15 women on AED monotherapy, increased seizure frequency in the first, second, and all trimesters was associated with a lower RTC (p < 0.05).

CONCLUSION

AED clearance significantly changes by the first trimester for levetiracetam and by the second trimester for oxcarbazepine and topiramate. Lower RTC was associated with seizure worsening. Early therapeutic drug monitoring and dose adjustment may be helpful to avoid increased seizure frequency.

Estrogen-related seizure exacerbation following hormone therapy for assisted reproduction in women with epilepsy

PURPOSE

Exogenous estrogens might lead to seizure worsening in women with epilepsy (WWE) by lowering the seizure threshold and inducing glucuronidation in women taking lamotrigine. Assisted reproduction techniques are increasingly used and often require estrogenic and estrogen raising hormone therapy. We aimed at reporting their possible impact on seizures in WWE.

METHODS

We describe two cases of seizure exacerbation following hormone therapy for assisted reproduction in WWE.

RESULTS

Patient 1: 46 years old woman, with right temporal dysplasia. At 40 years she had monthly focal seizures, possibly progressing to bilateral tonic-clonic seizures, she took levetiracetam 3000/day and she underwent gonadotropin therapy for ovarian stimulation. Estrogen blood levels showed a sudden and significant rise, up to 1019 pg/ml and she had a concomitant cluster of three tonic-clonic seizures in 24 h. Patient 2: 41 years old woman with focal epilepsy of unknown etiology. At 38 years she was taking lamotrigine 450 mg/day and had been seizure free for three years. She took estradiol valerate 4 mg for 10 days for endometrial preparation for embryo transfer and had the only seizure over six years, with the exception of auras during advanced pregnancy, related to marked decrease of lamotrigine blood levels. During adjunctive concomitant therapy with clobazam, neither patient had seizures while on hormone therapy.

CONCLUSIONS

Our data suggest that hormone therapy for assisted reproduction could exacerbate seizures and should be carefully monitored in WWE, especially those taking drugs inactivated by glucuronidation. Adjunctive concomitant antiepileptic therapy should be considered.

In Utero Oxcarbazepine Exposure and Neonatal Abstinence Syndrome: Case Report and Brief Review of the Literature

Oxcarbazepine is a second‐generation antiepileptic drug that is used to treat partial seizures. Although it has been increasingly used in pregnant women, its fetal safety has not been fully validated. We describe a 12‐hour‐old neonate who developed neonatal abstinence syndrome (NAS) after intrauterine exposure to oxcarbazepine. The neonate was born via cesarean section to a mother who took oxcarbazepine 300 mg/day for treatment of seizures throughout her pregnancy. Approximately 12 hours after birth, the infant developed paroxysmal jitter, which mainly presented as increased excitability, irritability, limb shaking, and increased muscle tone. These symptoms resolved by day 9 of life. Although NAS occurs most often after in utero exposure to opioids, exposure to other drugs during pregnancy may contribute to a small proportion of NAS cases. To our knowledge, this is the second case report of oxcarbazepine‐induced NAS. Pregnant women with epilepsy should weigh the pros and cons of continuing oxcarbazepine during their pregnancy when they are prescribed this drug. For infants with in utero oxcarbazepine exposure, comprehensive assessments and examinations are necessary for screening oxcarbazepine‐induced NAS.

Pregnancy-Associated Changes in Pharmacokinetics: A Systematic Review

BACKGROUND

Women are commonly prescribed a variety of medications during pregnancy. As most organ systems are affected by the substantial anatomical and physiological changes that occur during pregnancy, it is expected that pharmacokinetics (PK) (absorption, distribution, metabolism, and excretion of drugs) would also be affected in ways that may necessitate changes in dosing schedules. The objective of this study was to systematically identify existing clinically relevant evidence on PK changes during pregnancy.

METHODS AND FINDINGS

Systematic searches were conducted in MEDLINE (Ovid), Embase (Ovid), Cochrane Central Register of Controlled Trials (Ovid), and Web of Science (Thomson Reuters), from database inception to August 31, 2015. An update of the search from September 1, 2015, to May 20, 2016, was performed, and relevant data were added to the present review. No language or date restrictions were applied. All publications of clinical PK studies involving a group of pregnant women with a comparison to nonpregnant participants or nonpregnant population data were eligible to be included in this review. A total of 198 studies involving 121 different medications fulfilled the inclusion criteria. In these studies, commonly investigated drug classes included antiretrovirals (54 studies), antiepileptic drugs (27 studies), antibiotics (23 studies), antimalarial drugs (22 studies), and cardiovascular drugs (17 studies). Overall, pregnancy-associated changes in PK parameters were often observed as consistent findings among many studies, particularly enhanced drug elimination and decreased exposure to total drugs (bound and unbound to plasma proteins) at a given dose. However, associated alterations in clinical responses and outcomes, or lack thereof, remain largely unknown.

CONCLUSION

This systematic review of pregnancy-associated PK changes identifies a significant gap between the accumulating knowledge of PK changes in pregnant women and our understanding of their clinical impact for both mother and fetus. It is essential for clinicians to be aware of these unique pregnancy-related changes in PK, and to critically examine their clinical implications.

Issues for Women with Epilepsy

Epilepsy and antiepileptic drugs affect the menstrual cycle, aspects of contraception, reproductive health, pregnancy, and menopause through alteration of sex steroid hormone pathways. Sex steroid hormones often have an effect on seizure frequency and may alter the level of some antiepileptic drugs. Approximately one-third of women experience an increase in perimenstrual and/or periovulatory seizure frequency. Some women experience an increase in seizure frequency during pregnancy. Balancing maternal seizure control and the risk of congenital malformations associated with fetal antiepileptic drug exposure may be challenging. Some antiepileptic drugs are associated with cognitive and behavioral teratogenesis and should be avoided if possible during pregnancy.

Advances in anti-epileptic drug testing

In the past twenty-one years, 17 new antiepileptic drugs have been approved for use in the United States and/or Europe. These drugs are clobazam, ezogabine (retigabine), eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, perampanel, pregabalin, rufinamide, stiripentol, tiagabine, topiramate, vigabatrin and zonisamide. Therapeutic drug monitoring is often used in the clinical dosing of the newer anti-epileptic drugs. The drugs with the best justifications for drug monitoring are lamotrigine, levetiracetam, oxcarbazepine, stiripentol, and zonisamide. Perampanel, stiripentol and tiagabine are strongly bound to serum proteins and are candidates for monitoring of the free drug fractions. Alternative specimens for therapeutic drug monitoring are saliva and dried blood spots. Therapeutic drug monitoring of the new antiepileptic drugs is discussed here for managing patients with epilepsy.

Gender issues in antiepileptic drug treatment

The purpose of this review is to discuss gender-related aspects in the, pharmacokinetics, effects, selection and use of antiepileptic drugs (AED). In general, there are few known gender related differences in pharmacokinetics or efficacy of AEDs. Conversely, gender has a significant influence on the susceptibility to certain adverse effects, not the least those involving alterations in sex hormone metabolism. Particularly relevant are the teratogenic effects of AEDs, with important differences among AEDs in their potential to cause adverse effects on the fetus when used during pregnancy. Pregnancy can also markedly affect the pharmacokinetics of several AEDs, and dose adjustments are often needed during pregnancy to maintain seizure control. Some treatments that are used only by women, such as contraceptive steroids and hormone replacement therapy, can also interact with AEDs to an extent that may affect the utilization of both the AEDs and the other drug.

Use of antiepileptic drugs in pregnancy

Babies born to mothers exposed to antiepileptic drugs (AEDs) are at increased risk for major congenital malformations, cognitive impairment and fetal death. For the millions of women with epilepsy, maintaining the safest drug that will successfully prevent seizures during pregnancy remains a primary consideration. The recent development of collaborative international registries to examine the differential and dose-dependent effects of the expanding number of old and new AEDs, have shed light upon potential differences during pregnancy. Valproic acid appears to be associated with the highest risk of overall, as well as AED-specific, birth defects, becoming more evident as doses exceed 1000 mg/day. Lamotrigine may be less teratogenic to humans than other AEDs, although orofacial clefts have recently been reported. The effects of polytherapy appear to carry greater risks compared with monotherapy. Limited data exist for many of the newer AEDs. Furthermore, AED effects may persist during postnatal development. Although no class 1 outcome data are available, prepregnancy counseling to optimize patient-specific treatment is recommended for women of childbearing potential with epilepsy.

Women and epilepsy: review and practical recommendations

Individuals with epilepsy experience a number of sex-specific problems. In women, pregnancy and delivery are obvious issues, fertility problems are more often encountered and they also seem to have a higher frequency of sexual problems. A large number of women with epilepsy experience seizure exacerbation in relation to the menstrual cycle and have higher frequencies of menstrual disturbances and polycystic ovaries. Cosmetic problems affecting skin, hair or weight may also be drug induced. The use of antiepileptic drugs may influence the effect of contraceptives leading to unplanned pregnancies and contraceptives may affect the serum levels of antiepileptic drugs. The care of pregnant women with epilepsy requires attention to a number of guidelines and close cooperation between neurologist and gynecologist is recommended. Although the majority of the women with epilepsy experience normal pregnancies and deliveries, their children have a higher risk of birth defects. At menopause, their seizure pattern may change and some antiepileptic drugs may increase the risk of osteoporosis. The optimal treatment of women with epilepsy should take into account these gender-specific issues in the different stages of life.

Chiral chromatographic resolution of antiepileptic drugs and their metabolites: a challenge from the optimization to the application

A large number of the antiepileptic drugs (AEDs) presently available for clinical practice are chiral compounds while others, although achiral, may originate pharmacologically active chiral metabolites in vivo. The well-known implications of chirality in pharmacokinetics and pharmacodynamics demand the investigation of pharmacological properties for a racemic mixture and each enantiomer. To achieve these objectives, appropriate chiral analytical methods must be available. This article provides the first review of the current state of the art in chiral chromatographic methods available for quantifying enantiomers of AEDs in distinct matrices. Particular attention is paid to the methodological aspects and optimization strategies that successfully allow enantiomeric chromatographic separation of chiral AEDs and/or metabolites. Furthermore, the relevance of these methods in supporting the discovery and development of chiral AEDs is emphasized. In parallel and whenever available, the principal validation parameters are herein considered and related to the stage of drug discovery and development. In an attempt to optimize anticonvulsant activity and simultaneously diminish toxic effects, many pharmaceutical companies have started to manufacture single enantiomers. Therefore, chiral chromatographic techniques will be essential and the information herein compiled can be used as a framework for developing them.

Therapeutic drug monitoring in pregnancy

Therapeutic drug monitoring (TDM) is commonly recommended to optimize drug dosing regimens of various medications. It has been proposed to guide therapy in pregnant women, in whom physiological changes may lead to altered pharmacokinetics resulting in difficulty in predicting the appropriate drug dosage. Ideally, TDM may play a role in enhancing the effectiveness of treatment while minimizing toxicity of both the mother and fetus. Monitoring of drug levels may also be helpful in assessing adherence to prescribed therapy in selected cases. Limitations exist as therapeutic ranges have only been defined for a limited number of drugs and are based on data obtained in nonpregnant patients. TDM has been suggested for anticonvulsants, antidepressants, and antiretroviral drugs, based on pharmacokinetic studies that have shown reduced drug concentrations. However, there is only relatively limited (and sometimes inconsistent) information regarding the clinical impact of these pharmacokinetic changes during pregnancy and the effect of subsequent dose adjustments. Further studies are required to determine whether implementation of TDM during pregnancy improves outcome and is associated with any benefit beyond that achieved by clinical judgment alone. The cost effectiveness of TDM programs during pregnancy also remains to be examined.

Second-generation antiepileptic drugs and pregnancy: a guide for clinicians

When treating pregnant women with antiepileptic drugs (AEDs), clinicians have to balance potential fetal adverse effects against the risks of uncontrolled maternal disease. Only recently have emerging scientic data provided a rational basis for treatment decisions considering both aspects. The focus of research is currently moving from the first to the second AED generation. Lamotrigine is relatively well studied, and data on other novel AEDs, such as levetiracetam, oxcarbazepine, topiramate, zonisamide, gabapentin and pregabalin, are in progress. Safety issues appear to be favorable for lamotrigine, and preliminary results are also promising for levetiracetam and oxcarbazepine. Drugs metabolized by uridine-diphospate glucuronosyl transferase or excreted unchanged by the kidneys are particularly susceptible to increased body clearance during pregnancy. Lamotrigine is subject to both mechanisms, and therapeutic serum levels may sometimes be difficult to maintain. The authors review the recommendations and clinical research on modern AED treatment during pregnancy, highlighting current experience with second-generation drugs.

Managing epilepsy during pregnancy: assessing risk and optimizing care

OPINION STATEMENT

Epilepsy is the most common neurologic condition found in pregnancy. As such, all neurologists, internists, and obstetricians should know how to counsel women with epilepsy as they are considering pregnancy. While all of the usual recommendations for women of childbearing potential apply, including preconceptual and ongoing use of folic acid, calcium, and vitamin D, additional consideration must be given to the need for adjustment or change of anticonvulsant therapy. Monotherapy with the lowest dose of medication needed to control seizures should be prescribed prior to conception. Most anticonvulsants have a favorable profile when used in pregnancy; older anticonvulsants such as valproate and carbamazepine should be avoided, as they are associated with higher rates of fetal malformation, and in the case of valproate, with proven cognitive deficits in children exposed to this medication in utero. With use of any anticonvulsant medication, dosing throughout pregnancy will need to be adjusted to maintain an appropriate serum concentration. Dosing of anticonvulsants needs to be decreased after delivery to avoid medication-related toxicity, although sleep deprivation and hormonal fluctuation can increase the risk of seizures in postpartum women. With proper management, the majority of women with epilepsy can have uneventful pregnancies and healthy babies.

Host factors affecting antiepileptic drug delivery-pharmacokinetic variability

Antiepileptic drugs (AEDs) are the mainstay in the treatment of epilepsy, one of the most common serious chronic neurological disorders. AEDs display extensive pharmacological variability between and within patients, and a major determinant of differences in response to treatment is pharmacokinetic variability. Host factors affecting AED delivery may be defined as the pharmacokinetic characteristics that determine the AED delivery to the site of action, the epileptic focus. Individual differences may occur in absorption, distribution, metabolism and excretion. These differences can be determined by genetic factors including gender and ethnicity, but the pharmacokinetics of AEDs can also be affected by age, specific physiological states in life, such as pregnancy, or pathological conditions including hepatic and renal insufficiency. Pharmacokinetic interactions with other drugs are another important source of variability in response to AEDs. Pharmacokinetic characteristics of the presently available AEDs are discussed in this review as well as their clinical implications.

Population pharmacokinetics of artesunate and dihydroartemisinin in pregnant and non-pregnant women with malaria

Background

The World Health Organization endorses the use of artemisinin-based combination therapy for treatment of acute uncomplicated falciparum malaria in the second and third trimesters of pregnancy. However, the effects of pregnancy on the pharmacokinetics of artemisinin derivatives, such as artesunate (AS), are poorly understood. In this analysis, the population pharmacokinetics of oral AS, and its active metabolite dihydroartemisinin (DHA), were studied in pregnant and non-pregnant women at the Kingasani Maternity Clinic in the DRC.

Methods

Data were obtained from 26 pregnant women in the second (22 - 26 weeks) or the third (32 - 36 weeks) trimester of pregnancy and from 25 non-pregnant female controls. All subjects received 200 mg AS. Plasma AS and DHA were measured using a validated LC-MS method. Estimates for pharmacokinetic and variability parameters were obtained through nonlinear mixed effects modelling.

Results

A simultaneous parent-metabolite model was developed consisting of mixed zero-order, lagged first-order absorption of AS, a one-compartment model for AS, and a one-compartment model for DHA. Complete conversion of AS to DHA was assumed. The model displayed satisfactory goodness-of-fit, stability, and predictive ability. Apparent clearance (CL/F) and volume of distribution (V/F) estimates, with 95% bootstrap confidence intervals, were as follows: 195 L (139-285 L) for AS V/F, 895 L/h (788-1045 L/h) for AS CL/F, 91.4 L (78.5-109 L) for DHA V/F, and 64.0 L/h (55.1-75.2 L/h) for DHA CL/F. The effect of pregnancy on DHA CL/F was determined to be significant, with a pregnancy-associated increase in DHA CL/F of 42.3% (19.7 - 72.3%).

Conclusions

In this analysis, pharmacokinetic modelling suggests that pregnant women have accelerated DHA clearance compared to non-pregnant women receiving orally administered AS. These findings, in conjunction with a previous non-compartmental analysis of the modelled data, provide further evidence that higher AS doses would be required to maintain similar DHA levels in pregnant women as achieved in non-pregnant controls.

Therapeutic Drug Monitoring of the Newer Anti-Epilepsy Medications

In the past twenty years, 14 new antiepileptic drugs have been approved for use in the United States and/or Europe. These drugs are eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, pregabalin, rufinamide, stiripentol, tiagabine, topiramate, vigabatrin and zonisamide. In general, the clinical utility of therapeutic drug monitoring has not been established in clinical trials for these new anticonvulsants, and clear guidelines for drug monitoring have yet to be defined. The antiepileptic drugs with the strongest justifications for drug monitoring are lamotrigine, oxcarbazepine, stiripentol, and zonisamide. Stiripentol and tiagabine are strongly protein bound and are candidates for free drug monitoring. Therapeutic drug monitoring has lower utility for gabapentin, pregabalin, and vigabatrin. Measurement of salivary drug concentrations has potential utility for therapeutic drug monitoring of lamotrigine, levetiracetam, and topiramate. Therapeutic drug monitoring of the new antiepileptic drugs will be discussed in managing patients with epilepsy.

Therapeutic Drug Monitoring of the Newer Anti-Epilepsy Medications

In the past twenty years, 14 new antiepileptic drugs have been approved for use in the United States and/or Europe. These drugs are eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, pregabalin, rufinamide, stiripentol, tiagabine, topiramate, vigabatrin and zonisamide. In general, the clinical utility of therapeutic drug monitoring has not been established in clinical trials for these new anticonvulsants, and clear guidelines for drug monitoring have yet to be defined. The antiepileptic drugs with the strongest justifications for drug monitoring are lamotrigine, oxcarbazepine, stiripentol, and zonisamide. Stiripentol and tiagabine are strongly protein bound and are candidates for free drug monitoring. Therapeutic drug monitoring has lower utility for gabapentin, pregabalin, and vigabatrin. Measurement of salivary drug concentrations has potential utility for therapeutic drug monitoring of lamotrigine, levetiracetam, and topiramate. Therapeutic drug monitoring of the new antiepileptic drugs will be discussed in managing patients with epilepsy.

[Therapeutic drug monitoring of oxcarbazepine]

Oxcarbazepine is an analogue of carbamazepine, used for the treatment of partial seizure with or without secondary generalization. The two forms R and S of the mono-hydroxylated derivatives (MHD) are responsible for most of the anti-convulsant activity and it is the concentrations of MHD that are relevant in therapeutic drug monitoring (TDM). Analysis of currently literature provides no well-established relationship between plasma concentration of MHD and efficiency or toxicity. Although there is not a validated therapeutic range, the residual concentrations of usually observed therapeutic MHD are situated between 12 and 30 mg/L. In certain pathological or physiological circumstances, the pharmacokinetic variability of the oxcarbazepine can be considerable, but this strong unpredictability does not nevertheless justify the TDM of the MHD. Based on the available evidence, TDM of MHD is not routinely warranted but may be possibly useful in specific situations such as pregnancy or renal insufficiency.

Pharmacokinetics of topiramate during pregnancy

PURPOSE

To study the effects of pregnancy on plasma concentrations of topiramate (TPM).

METHODS

An established routine fluorescence polarization immunoassay (FPIA) method was used to determine TPM concentrations in 15 women with epilepsy treated with TPM during altogether 17 pregnancies.

RESULTS

In 10 pregnancies, where samples were available from all three trimesters, the mean TPM dose/concentration ratio (D/C-ratio) was significantly higher than outside pregnancy baseline value 37.3 L/day (+/-15.9), during the 2nd, 67.5L/day (+/-23.4), and the 3rd trimester, 65.1L/day (+/-30.4), but not during the 1st, 49.4 L/day (+/-29.4). Including seven additional pregnancies enrolled late with data only from the 3rd trimester, the mean D/C-ratio during the 3rd trimester was 67.4 L/day (+/-27.5) compared to baseline, 38.8L/day (+/-18.0), an average increase by 71.8%. There was a pronounced intra-individual variability in alterations in D/C-ratios during pregnancies.

CONCLUSIONS

Our data show a significant pregnancy-related increase in D/C-ratios of TPM suggesting that therapeutic drug monitoring might be of value.

Managing antiepileptic drugs during pregnancy and lactation

PURPOSE OF REVIEW

This review discusses data on the pharmacokinetics of antiepileptic drugs (AEDs) in pregnancy and lactation, and the clinical consequences thereof, thus providing a basis for a rational management of AEDs during pregnancy and lactation.

RECENT FINDINGS

Studies have confirmed that the elimination of lamotrigine and the active metabolite of oxcarbazepine is enhanced during pregnancy. It has been established that the increased clearance of lamotrigine is caused by induction of glucuronidation. Also, the plasma concentrations of levetiracetam decline in pregnancy but the mechanism for this effect is yet to be explored. Lamotrigine is eliminated slowly in breast-fed infants, but although lamotrigine concentrations in the infant can reach pharmacological levels, no studies have reported clinically relevant adverse effects caused by lactation.

SUMMARY

Knowledge of the pharmacokinetics of AEDs in pregnancy and during lactation is important to enable optimal treatment. Gestation induced alterations in pharmacokinetics vary with the AED but also between patients and are difficult to predict. Therapeutic drug monitoring is, therefore, advisable during pregnancy and the use of the individual patient's optimal prepregnancy drug level is recommended as reference. Breastfeeding is in general safe but needs appropriate observation of the nursing infant.

Managing epilepsy in women of childbearing age

Epilepsy affects the menstrual cycle, aspects of contraception, fertility, pregnancy and bone health in women. It is common for seizure frequency to vary throughout the menstrual cycle. In ovulatory cycles, two peaks can be seen around the time of ovulation and in the few days before menstruation. In anovulatory cycles, there is an increase in seizures during the second half of the menstrual cycle. There is also an increase in polycystic ovaries and hyperandrogenism associated with valproate therapy. There are no contraindications to the use of non-hormonal methods of contraception in women with epilepsy. Non-enzyme-inducing antiepileptic drugs (AEDs) [valproate, benzodiazepines, ethosuximide, levetiracetam, tiagabine and zonisamide] do not show any interactions with the combined oral contraceptive (OC). There are interactions between the combined OC and hepatic microsomal-inducing AEDs (phenytoin, barbiturates, carbamazepine, topiramate [dosages>200 mg/day], oxcarbazepine) and lamotrigine. Pre-conception counselling should be available to all women with epilepsy who are considering pregnancy. Women with epilepsy should be informed about issues relating to the future pregnancy, including methods and consequences of prenatal screening, fertility, genetics of their seizure disorder, teratogenicity of AEDs, folic acid and vitamin K supplements, labour, breast feeding and care of a child. During pregnancy, the lowest effective dose of the most appropriate AED should be used, aiming for monotherapy where possible. Recent pregnancy databases have suggested that valproate is significantly more teratogenic than carbamazepine, and the combination of valproate and lamotrigine is particularly teratogenic. Most pregnancies in women with epilepsy are without complications, and the majority of infants are delivered healthy with no increased risk of obstetric complications in women. There is no medical reason why a woman with epilepsy cannot breastfeed her child. The AED concentration profiled in breast milk follows the plasma concentration curve. The total amount of drug transferred to infants via breast milk is usually much smaller than the amount transferred via the placenta during pregnancy. However, as drug elimination mechanisms are not fully developed in early infancy, repeated administration of a drug such as lamotrigine via breast milk may lead to accumulation in the infant. Studies have suggested that women with epilepsy are at increased risk of fractures, osteoporosis and osteomalacia. No studies have been undertaken looking at preventative therapies for these co-morbidities.

Influences on seizure activity in pregnant women with epilepsy

This study evaluated whether referral to a specialized epilepsy clinic prior to pregnancy influences seizure activity during pregnancy. In addition, folic acid supplementation prior to pregnancy as a marker of intent to conceive was used to evaluate whether the use of folic acid at the time of conception correlates with the risk of seizure deterioration in pregnancy. The study population consisted of patients who had been followed in a specialized epilepsy clinic before conception (group 1, n=46) and patients who were referred to the clinic after the pregnancy was recognized (group 2, n=44). Seizure deterioration was significantly lower in group 1 than in group 2: 9% versus 32% (P<0.01). In addition, the likelihood of having taken folic acid supplements was significantly higher in group 1 (P<0.001). With some methodological limitations taken into account, it is concluded that women followed in a specialized epilepsy clinic have a lower risk of seizure deterioration during pregnancy compared with those referred after conception.

Pregnancy and epilepsy: what should we tell our patients?

Women with epilepsy that plan to become pregnant can in general look forward to uneventful pregnancies and to giving birth to normal children. However, there are certain risks associated with epilepsy and antiepileptic drug (AED) treatment, and it is likely that these risks can be reduced with appropriate prepregnancy counseling. Women with epilepsy should be informed that maintained control of tonic-clonic seizures is important for their health as well as for the well-being of the fetus; that pregnancy in general has little effect on seizure control; but that pregnancy may affect plasma concentrations of AEDs, and that drug level monitoring and dosage adjustments may be needed. They should be informed of the moderately increased risk of birth defects, and that this risk appears to be higher with the use of valproate, in particular at doses above 800 mg/day. The possibility of changing from valproate to another AED should be considered, but such changes should be tried out before conception. Withdrawing or changing an AED should generally be avoided during pregnancy. Women with epilepsy on AED treatment should be encouraged to breast-feed.

Seizure deterioration in women treated with oxcarbazepine during pregnancy

Thirteen pregnancies in ten women on oxcarbazepine (OXC) monotherapy and one pregnancy in a woman on OXC and topiramate therapy were retrospectively analyzed. A significant decrease of ratio plasma concentration of 10-monohydroxy derivate (MHD) of oxcarbazepine to dosage was found by 26.2% during first trimester, by 36.5% during second trimester and by 38.2% during third trimester when compared to pre-pregnant levels. Eight patients experienced seizure deterioration during the pregnancy, five of which had been seizure-free before the pregnancy. In seven pregnancies (50%) the seizure frequency was at least doubled during pregnancy compared to a pre-pregnancy baseline. There was a trend toward a correlation between seizure deterioration and decrease in plasma concentration of MHD.

Epileptic disorders in pregnancy: an overview

PURPOSE OF REVIEW

Much new information has now become available regarding outcomes of women with epilepsy (WWE) and pregnancy.

RECENT FINDINGS

Valproate is associated with a risk of major congenital malformations within a range of 6.2-10.7%, though antiepileptic drugs (AEDs) other than valproate when used as monotherapy are associated with major congenital malformation rates ranging from 2.9 to 3.6%; the rate of major congenital malformations in WWE not treated with AEDs was similar to this at 3.1%. Seizure freedom in 9-12 months before pregnancy is associated with seizure freedom during pregnancy. A decline in AED levels can be expected during pregnancy, most dramatically for lamotrigine (but with marked variability between patients) and least with carbamazepine. Neonates born to WWE taking AEDs who receive vitamin K 1 mg intramuscularly at birth are not at additional risk of hemorrhagic disease of the newborn.

SUMMARY

The use of valproate and polytherapy with any AED combinations should be avoided, if clinically appropriate, during pregnancy. Seizure freedom in 9-12 months before pregnancy should be a goal. AED levels should be maintained at or near the therapeutic level known for that individual patient, with frequent monitoring during pregnancy as appropriate for the patient and the AED.

Changes in lamotrigine pharmacokinetics during pregnancy and the puerperium

To assess changes in the pharmacokinetics of the anti-epileptic drug lamotrigine (LTG) during pregnancy, plasma LTG concentrations at steady-state were determined at different intervals during 11 pregnancies in 10 women with epilepsy stabilized on long-term LTG therapy. In the five pregnancies that could be assessed both during gestation and after delivery, plasma LTG concentrations increased on average by 164% (range +75 to +351%) between the last observation during pregnancy and the puerperium (P < 0.05). When all pregnancies monitored during pregnancy were considered, plasma LTG concentrations declined by an average of 20% (range -64% to +13%) between the first and the last assessment before delivery. These findings confirm that plasma LTG concentrations decrease markedly during pregnancy and that, at least in some cases, this effect occurs as early as the first trimester. Because there is a large interindividual variability in the magnitude and time course of the pregnancy-associated pharmacokinetic changes, it is desirable to establish baseline plasma LTG concentrations in all women of childbearing potential and to monitor LTG levels at frequent intervals during pregnancy and the puerperium.

Antiepileptic drugs during pregnancy: what is known and which AEDs seem to be safest?

Most infants born to women with epilepsy are healthy, but there are increased risks related to in utero antiepileptic drug (AED) exposure and seizures. Emerging data from pregnancy registries and other studies allow us to better balance the anatomic teratogenic and neurodevelopmental effects of AEDs against the need to maintain maternal seizure control. Several large prospective pregnancy registries demonstrate a consistent pattern of increased risk for major congenital malformations (MCMs) with valproate (VPA) use as monotherapy, compared to nonexposed populations and to other AEDs used in monotherapy. AED polytherapy likely increases risk for MCMs, but the risk is more pronounced if VPA is included. Reduced cognitive outcomes have been reported with AED polytherapy, and with use of VPA, phenobarbital (PB), and PHT as monotherapy. Dose-dependent risk has been demonstrated with VPA for MCMs and cognitive consequences. CBZ groups show normal neurodevelopment. Increased clearance of most of the AEDs occurs during pregnancy. Use of therapeutic drug monitoring during pregnancy with LTG reduces the risk for seizure worsening. The consistent findings of increased teratogenic risk for VPA should discourage use of this medication as first-line treatment in women of childbearing age.

Serum concentration/dose ratio of topiramate during pregnancy

PURPOSE

To study the impact of pregnancy on the serum concentration/dose ratio (C/D-ratio) of topiramate (TPM).

METHODS

Twelve women with epilepsy using TPM during pregnancy, and 15 pregnancies were studied. The main target variable was the C/D-ratio at baseline and during pregnancy. Additional variables were changes in TPM dose, concomitant use of other antiepileptic drugs, seizure frequency, and pregnancy outcome. Clinical and pharmacological data were obtained from the women's medical records.

RESULTS

The average C/D-ratios in the second and third trimester were 30% (p = 0.002, n = 11) and 34% (p = 0.001, n = 8) lower than the baseline values, respectively. The interindividual variability was pronounced. Increased seizure frequency was common in pregnant women using TPM, but a correlation to the decline in TPM C/D-ratio could not be established from our data.

DISCUSSION

Dose-corrected serum concentrations of TPM appear to decline gradually throughout pregnancy. The underlying mechanisms are not known. Increased glomerular filtration may play a major role. During pregnancy, therapeutic drug monitoring of TPM may be useful.