Pharmacokinetics and Therapeutic Drug Monitoring of Newer Antiepileptic Drugs During Pregnancy and the Puerperium

Reproductive and fetal toxicity studies of histamine H3 receptor antagonist DL76 used in mice to prevent maximal electroshock-induced seizure

Introduction: Brain histamine is considered an endogenous anticonvulsant and histamine H1 receptor. H1R antagonists have, in earlier studies, been found to induce convulsions. Moreover, research during the last two decades has provided more information concerning the anticonvulsant activities of histamine H3R (H3R) antagonists investigated in a variety of animal epilepsy models. Methods: Therefore, the in vivo anticonvulsant effect of the H3R antagonist DL76, with proven high in vitro affinity, in vitro selectivity profile, and high in vivo antagonist potency in mice against maximal electroshock (MES)-induced seizures in mice, was assessed. Valproic acid (VPA) was used as a reference antiepileptic drug (AED). In addition, DL76 was tested for its reproductive and fetal toxicity in the same animal species. Results and discussion: Our observations showed that acute systemic administration (intraperitoneal; i.p.) of DL76 (7.5 mg/kg, 15 mg/kg, 30 mg/kg, and 60 mg/kg, i.p.) provided significant and dose-dependent protection against MES-induced seizures in female and male mice. Moreover, the DL76-provided protective effects were comparable to those offered by the VPA and were reversed when animals were co-administered the CNS-penetrant selective H3R agonist R-(α)-methylhistamine (RAM, 10 mg/kg, i.p.). Furthermore, the administration of single (7.5 mg/kg, 15 mg/kg, 30 mg/kg, or 60 mg/kg, i.p.) or multiple doses (3 × 15 mg/kg, i.p.) of H3R antagonist DL76 on gestation days (GD) 8 or 13 failed to affect the maternal body weight of mice when compared with the control mice group. No significant alterations were detected in the average number of implantations and resorptions between the control and DL76-treated groups at the early stages of gestation and the organogenesis period. In addition, no significant differences in the occurrence of skeletal abnormalities, urogenital abnormalities, exencephaly, exomphalos, facial clefts, and caudal malformations were observed. The only significant abnormalities witnessed in the treated groups of mice were in the length of long bones and body length. In conclusion, the novel H3R antagonist DL76 protected test animals against MES-induced seizures and had a low incidence of reproductive and fetal malformation with decreased long bone lengths in vivo, signifying the potential therapeutic value of H3R antagonist DL76 for future preclinical as well as clinical development for use in the management of epilepsy.

Issues of Women with Epilepsy and Suitable Antiseizure Drugs

Seizure aggravation in women with epilepsy (WWE) tends to occur at two specific times during the menstrual cycle: the perimenstrual phase and the ovulation period. Antiseizure drugs (ASDs), especially those that induce enzymes, can accelerate the metabolism of hormones in oral contraceptives, rendering them less effective. Estrogen in contraceptive pills increases the metabolism of lamotrigine. Physiological changes during pregnancy can significantly impact the pharmacokinetics of ASDs, potentially necessitating adjustments in dosage for women with epilepsy to maintain seizure control. The use of valproate in pregnant women is associated with the highest risk of major congenital malformations among ASDs. Risks of major congenital malformations associated with lamotrigine, levetiracetam, and oxcarbazepine were within the range reported in the general population. Exposure to valproate can lead to lower IQ in offspring. Reduced folic acid levels are linked to orofacial clefts, cardiovascular malformations, and urogenital and limb anomalies in WWE. Decreased folate levels are expected with the use of enzyme-inducing ASDs. However, a high dose of folate was associated with an increased risk of cancer in children of mothers with epilepsy. Most ASDs are generally considered safe for breastfeeding and should be encouraged. However, no single ASD is considered ideal for childbearing WWE. Lamotrigine and levetiracetam are relatively more suitable options for this situation.

Changes in seizure frequency and anti-seizure medication therapy during pregnancy and one year postpregnancy

Seizure control in women with epilepsy (WWE) during pregnancy is a vital concern. The aim of this study was to compare changes in seizure frequency and anti-seizure medication (ASM ) therapy in WWE in a real-world setting over three epochs (prepregnancy, pregnancy, and postpregnancy). We screened WWE who were pregnant between 1 January 2010 and 31 December 2020 from the epilepsy follow-up registry database of a tertiary hospital in China. We reviewed and collected follow-up data for the following time periods: 12 months before pregnancy (epoch 1), throughout pregnancy and the first 6 weeks postpartum (epoch 2), and from 6 weeks to 12 months postpartum (epoch 3). Seizures were classified into two categories: tonic‒clonic/focal to bilateral tonic‒clonic seizures and non-tonic‒clonic seizures. The main indicator was the seizure-free rate over the three epochs. Using epoch 1 as a reference, we also compared the percentage of women with an increased seizure frequency, as well as changes in ASM treatment, in epochs 2 and 3. Ultimately, 271 eligible pregnancies in 249 women were included. The seizure-free rates in epoch 1, epoch 2, and epoch 3 were 38.4%, 34.7%, and 43.9%, respectively (P = 0.09). The top three ASMs used in the three epochs were lamotrigine, levetiracetam, and oxcarbazepine. Using epoch 1 as a reference, the percentages of women with increased frequencies of tonic‒clonic/focal to bilateral tonic‒clonic seizures in epoch 2 and epoch 3 were 17.0% and 14.8%, respectively, while the percentages of women with an increased frequency of non-tonic‒clonic seizures in epoch 2 and epoch 3 were 31.0% and 21.8% (P = 0.02). The percentage of women whose ASM dosages were increased in epoch 2 was higher than that in epoch 3 (35.8% vs. 27.3%, P = 0.03). The seizure frequency during pregnancy may not differ significantly from that during prepregnancy and postpregnancy if WWE are treated according to the guidelines.

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.

Current safety concerns about the use of antiseizure medications in pregnancy

INTRODUCTION

Given the high prevalence of epilepsy in women of childbearing potential (15 million out of 50 million people worldwide), antiseizure medication (ASM) use in pregnancy is common. Identifying the safest and most effective ASM to use during pregnancy is often difficult, but also crucially important. The challenge is to balance two needs: maintaining seizure control while minimizing teratogenicity.

AREAS COVERED

This review looks at seizure- and treatment-related risks to mother and fetus during pregnancy, existing healthcare information programmes, strengths and pitfalls of the main pregnancy registries, known and supposed pharmacokinetic changes during gestation, the utility of therapeutic drug monitoring, and safety concerns. Articles and related content were screened on available publications after January 2000.

EXPERT OPINION

The use of newer ASMs during pregnancy is still limited, as shown by the paucity of data collected by different pregnancy registries. Choosing these medications can be challenging, partly due to unknown pharmacokinetic modifications in pregnancy, an aspect that serum drug monitoring might help to clarify. The safest treatment is chosen also taking into account the woman's needs, concerns and wishes, but adequate pre-pregnancy counseling is necessary to properly inform her about personal and fetal risks related both to seizures and to medications.

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.

Epilepsy and pregnancy: identifying risks

Pregnancy is a time of physical, physiological and psychological challenge. For women with epilepsy, as well as its potential for joy and fulfilment, pregnancy may bring additional risks and difficulties. Clinicians must anticipate and prevent these complications, ensuring that pregnancy, delivery and motherhood proceed without obstetric or medical complications, using available evidence to balance individual risks of undertreatment and overtreatment. Here we review epilepsy management in pregnancy, identifying some of the known effects of epilepsy and its treatment on gestation, fetal malformation, delivery, and neurocognitive and behavioural development. We outline strategies to reduce obstetric and fetal complications in women with epilepsy, while recognising the sometimes competing need to maintain or improve seizure control. We reinforce the importance of identifying those at highest risk, who may require additional measures or safeguards.

Therapeutic drug monitoring of newer generation antiseizure medications at the point of treatment failure

PURPOSE

The benefit of therapeutic drug monitoring (TDM) of newer generation antiseizure medications (ASM) has been little studied. A recent randomized study suggested that TDM at each medical visit did not bring a significant benefit, but the study did not investigate TDM in cases of treatment failure. Accordingly, we realized a post hoc analysis of this trial.

METHODS

We analyzed 282 TDMs in 136 patients. We compared TDM performed at visits after treatment failure versus without treatment failure, reporting the proportion of drug levels out of range and the prescriber's adherence to dosage recommendations according to measured drug levels.

RESULTS

There was no statistical difference in terms of proportion of out of range plasma drug levels (47% vs 50%, p = 0.7) or adherence of prescribers to the clinical pharmacologists' dosage recommendations (21% vs 30%, p = 0.6) between visits after treatment failure and visits without treatment failure, respectively. Knowledge of prior drug levels did not modify the results.

CONCLUSION

Systematic TDM at appointments following treatment failure showed similar results to TDM at visits without treatment failure. The prescribers' adherence with dosage recommendations was low in both cases. It is not clear whether better prescriber adherence would improve patient outcome. Furthermore, the ability to detect poor patient compliance is limited in a planned outpatient appointment. The study setting does not reflect on the general usefulness of TDM.

Levetiracetam, lamotrigine and carbamazepine: which monotherapy during pregnancy?

OBJECTIVE

Epilepsy treatment during pregnancy is still challenging. The study is aimed at comparing the efficacy and safety of carbamazepine (CBZ), lamotrigine (LTG) and levetiracetam (LEV) monotherapies during pregnancy in women with focal (FE) or generalized (GE) epilepsy.

METHODS

A multicentre retrospective study was conducted to evaluate seizures frequency and seizure freedom (SF) rate during 3 months before pregnancy, each trimester of gestation and post-partum period in women on monotherapy with CBZ, LTG and LEV.

RESULTS

Fifty-seven pregnancies (45 FE, 12 GE) on monotherapy (29 CBZ, 11 LTG, 17 LEV) were included. A significant reduction of seizure frequency was found in the first trimester of pregnancy as compared with that one before pregnancy (p = 0.004), more evident in GE (p = 0.003) and in LEV group (p = 0.004). The SF rate significantly increased in the first trimester in comparison to that one before pregnancy and persisted in the post-partum period in the whole sample (p < 0.001) and in women on LEV (p = 0.004). Besides, 88.57% of SF women before pregnancy remained unchanged during gestation and the post-partum period. One major heart malformation in CBZ and no major malformations in LTG and LEV groups were found.

CONCLUSIONS

A better clinical outcome during pregnancy emerged since the first trimester in comparison to the before-pregnancy period, mostly evident in women with GE and LEV therapy, reinforcing the hypothesis of a protective role of pregnancy versus seizures. SF before pregnancy represents a significant predictive factor of good clinical outcome during gestation and the post-partum period. Compared to CBZ, LTG and LEV showed a better safety profile.

Therapeutic Drug Monitoring of Antiepileptic Drugs in Women with Epilepsy Before, During, and After Pregnancy

During pregnancy, the pharmacokinetics of an antiepileptic drug is altered because of changes in the clearance capacity and volume of distribution. These changes may have consequences for the frequency of seizures during pregnancy and fetal exposure to antiepileptic drugs. In 2009, a review was published providing guidance for the dosing and therapeutic drug monitoring of antiepileptic drugs during pregnancy. Since that review, new drugs have been licensed and new information about existing drugs has been published. With this review, we aim to provide an updated narrative overview of changes in the pharmacokinetics of antiepileptic drugs in women during pregnancy. In addition, we aim to formulate advice for dose modification and therapeutic drug monitoring of antiepileptic drugs. We searched PubMed and the available literature on the pharmacokinetic changes of antiepileptic drugs and seizure frequency during pregnancy published between January 2007 and September 2018. During pregnancy, an increase in clearance and a decrease in the concentrations of lamotrigine, levetiracetam, oxcarbazepine's active metabolite licarbazepine, topiramate, and zonisamide were observed. Carbamazepine clearance remains unchanged during pregnancy. There is inadequate or no evidence for changes in the clearance or concentrations of clobazam and its active metabolite N-desmethylclobazam, gabapentin, lacosamide, perampanel, and valproate. Postpartum elimination rates of lamotrigine, levetiracetam, and licarbazepine resumed to pre-pregnancy values within the first few weeks after pregnancy. We advise monitoring of antiepileptic drug trough concentrations twice before pregnancy. This is the reference concentration. We also advise to consider dose adjustments guided by therapeutic drug monitoring during pregnancy if the antiepileptic drug concentration decreases 15-25% from the pre-pregnancy reference concentration, in the presence of risk factors for convulsions. If the antiepileptic drug concentration changes more than 25% compared with the reference concentration, dose adjustment is advised. Monitoring of levetiracetam, licarbazepine, lamotrigine, and topiramate is recommended during and after pregnancy. Monitoring of clobazam, N-desmethylclobazam, gabapentin, lacosamide, perampanel, and zonisamide during and after pregnancy should be considered. Because of the risk of teratogenic effects, valproate should be avoided during pregnancy. If that is impossible, monitoring of both total and unbound valproate is recommended. More research is needed on the large number of unclear pregnancy-related effects on the pharmacokinetics of antiepileptic drugs.

[Significant Changes Associated with the Transition from Outsourcing to In-hospital Therapeutic Drug Monitoring of Novel Antiepileptics]

For many of the novel antiepileptics, immunoassays, used for routine therapeutic drug monitoring (TDM), cannot be used. We could monitor eight novel antiepileptics using an LC/MS method since July 2017. The purpose of this study was to evaluate the significant changes associated with the transition from outsourcing to in-hospital monitoring of novel antiepileptics. The number of measurements of novel antiepileptics was significantly increased during the first (p<0.01) and second (p<0.001) years of in-hospital monitoring as compared to that one year prior to in-hospital monitoring which was outsourced. The proportion of measurements of novel antiepileptics to all antiepileptics was 19.7%, 31.1%, and 38.4% during outsourcing, and first, and second years of in-hospital monitoring, respectively. The measurement cost was significantly reduced during the first (p<0.001) and second (p<0.001) years of in-hospital monitoring as compared to that during outsourcing. In addition, the revenue from TDM of antiepileptic drugs was significantly increased during the first (p<0.05) and second (p<0.01) years of in-hospital monitoring as compared with that during outsourcing. In conclusion, the switch from outsourcing to in-hospital monitoring led to an increase in the number of orders, a reduction in the measurement-related expenses of novel antiepileptics, and an increase in the revenue from TDM of antiepileptic drugs, which could promote the proper use of novel antiepileptics through TDM.

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).

Therapeutic strategies for treating epilepsy during pregnancy

INTRODUCTION

Counseling for women with epilepsy of childbearing potential surrounding pregnancy issues is of the utmost importance and should be done when antiepileptic medications are prescribed and reviewed regularly at clinic visits. Physicians must be familiar with risks associated with antiepileptic medication, and endeavor to minimize risks to a fetus while selecting best medications for epilepsy type.

AREAS COVERED

The authors discuss the role of folic acid, updated evidence relating to the occurrence of major congenital malformations and neurocognitive risks associated with antiepileptic medication. They also examine the rationale for monitoring drug levels, optimum delivery strategies, and evidence for the safety of breastfeeding while taking antiepileptic medication.

EXPERT OPINION

Valproate carries the highest known teratogenic risk in pregnancy and should only be prescribed to women of child-bearing potential in a specialist setting. There is a need for the ongoing register collection of risks associated with newer AEDs which lack substantial (major) data. Choosing these newer medications can create a dilemma for physicians, particularly when seizures are not well controlled or where treatment options are limited. The authors advocate a multidisciplinary team approach to managing women with epilepsy so that pregnancies in such women can be well managed in an optimum and individualized fashion.

Anticonvulsant and reproductive toxicological studies of the imidazole-based histamine H3R antagonist in mice

The imidazole-based H3R antagonist 2-18 with high in vitro H3R antagonist affinity, excellent in vitro selectivity profile, and high in vivo H3R antagonist potency was tested for its anticonvulsant effect in maximal electroshock (MES)-induced convulsions in mice having valproic acid (VPA) as a reference antiepileptic drug (AED). Additionally, H3R antagonist 2-18 was evaluated for its reproductive toxicity in the same animal species. The results show that acute systemic administration (intraperitoneal; i.p.) of H3R antagonist 2-18 (7.5, 15, 30, and 60 mg/kg, i.p.) significantly and dose dependently protected male as well as female mice against MES-induced convulsion. The protective action observed for H3R antagonist 2-18 in both mice sexes was comparable to that of VPA and was reversed when mice were pretreated with the selective H3R agonist (R)-alpha-methylhistamine (RAMH, 10 mg/kg, i.p.). Moreover, the results show that acute systemic administration of single (7.5, 15, 30, or 60 mg/kg, i.p.) or multiple doses (15×3 mg/kg, i.p.) of H3R antagonist 2-18 on gestation day (GD) 8 or 13 did not affect the maternal body weight of mice when compared with the control group. Furthermore, no significant differences were observed in the average number of implantations and resorptions between the control and H3R antagonist 2-18-treated group at the early stages of gestation and the organogenesis period. However, oral treatment with H3R antagonist 2-18 (15 mg/kg) on GD 8 induced a reduced number of live embryos when compared with the i.p.-treated mice. In addition, no significant changes in the fetal body and placental weights were observed after injection of H3R antagonist 2-18 with all selected doses. However, three dose groups of i.p. and oral 15 mg/kg on GD 13 significantly affected the placental weight when compared with control group. Notably, the treatment of pregnant female with the H3R antagonist 2-18 did not produce significant malformation in the fetus in both groups. In conclusion, the novel H3R antagonist 2-18 proves to be a very safe compound and displays a low incidence of malformations, demonstrating that H3R antagonist 2-18 may have a potential future therapeutic value in epilepsy.

Use of Antiepileptic Drugs During Pregnancy: Evolving Concepts

Although prenatal exposure to antiepileptic drugs (AEDs) is known to impart relatively higher risks of major congenital malformations, prospective studies have provided refined data that allow us to differentiate the risks of different types and doses of AEDs. As the number of AED prescriptions has dramatically increased in reproductive-aged women with a variety of neuropsychiatric indications, the evolving concepts learned from studies in women with epilepsy can be applied to a much larger group of pregnant women to improve child outcomes while maintaining maternal disease control. In addition to careful selection of the type of medication, the amount of fetal exposure at conception and in the first trimester probably matters across all AEDs. Some AED polytherapy regimens are not associated with a higher risk of malformations, although other outcomes have not yet been formally studied. The individual woman's drug target concentration should be established preconception and maintained during pregnancy, to prevent seizure worsening. Substantial pharmacokinetic changes occur with many of the medications during pregnancy and postpartum, and interindividual variability supports the use of therapeutic drug monitoring for most AEDs. During pregnancy, vigilance and close monitoring should also include intrauterine fetal growth, obstetric complications, and neonatal complications. Breastfeeding can provide additional neurodevelopmental benefit and should be an option for women on AEDs. Knowledge of these key principles enhances our ability to make treatment recommendations with resultant improved maternal and child outcomes. Additional prospective studies are needed to further define the risk-benefit ratio across a variety of medications, dosing strategies, and neuropsychiatric disorders.

Bipolar Depression: Pregnancy, Postpartum, and Lactation

Medication management of bipolar depression in pregnancy and lactation is best done by assessing each patient's and family's needs in detail. Keeping pregnant patients as psychiatrically stable as possible is the most important principle for clinicians. Unfortunately, there is no risk-free situation for patients with psychiatric illness. This is often the most difficult and hard to accept reality for these patients, families, and clinicians. Clinicians serve these patients best by being as transparent as possible about the risk/benefit analysis of each patient's situation with the realization that ultimately the decisions are made by the patient and family.

Management of epilepsy during pregnancy: an update

The clinical management of women with epilepsy on antiepileptic drugs (AEDs) during pregnancy presents unique challenges. The goal of treatment is optimal seizure control with minimal in utero fetal exposure to AEDs in an effort to reduce the risk of structural and neurodevelopmental teratogenic effects. This paper reviews the following key issues pertaining to women with epilepsy during pregnancy: AED pharmacokinetics; clinical management of AEDs; seizure frequency; major congenital malformation; neurodevelopmental outcomes; perinatal complications; and breast feeding.

Management of epilepsy during pregnancy: evidence-based strategies

Child-bearing years are often the most precarious management period in the life of a woman with epilepsy. This article reviews the results of many different studies with findings that enable the healthcare team to make confident decisions and recommendations during these critical periods. Preconceptional planning, effective contraception and folic acid supplementation are important fundamentals in preparation for pregnancy. There is growing evidence to avoid valproic acid use during the child-bearing years. Emerging data on congenital malformations and neurocognitive outcomes are available for some of the second-generation antiepileptic drugs and appear reassuring for lamotrigine and levetiracetam. Also reviewed are the benefits of postpartum drug tapers and favorable breastfeeding facts. Counseling the mother and her family on medication choices enables the healthcare team to implement informed decisions that are beneficial for the mother and child.

Long-term consequences after exposure to antiepileptic drugs in utero

Most pregnant women with epilepsy need pharmacological treatment during pregnancy. Children exposed to antiepileptic drugs have an increased risk of being born with major malformations. Some antiepileptic drugs seem to have negative effects on psychomotor or cognitive development in children exposed during foetal life. Neither carbamazepine nor lamotrigine in monotherapy seem to affect the cognition of exposed children. Several studies have shown negative effects on the long-term neurodevelopment of children prenatally exposed to valproic acid or polytherapy (two or more antiepileptic drugs during pregnancy). For most of the newer antiepileptic drugs there are insufficient data regarding long-term outcome.

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.

Pharmacotherapy for mood disorders in pregnancy: a review of pharmacokinetic changes and clinical recommendations for therapeutic drug monitoring

OBJECTIVE

Pharmacotherapy for mood disorders during pregnancy is often complicated by pregnancy-related pharmacokinetic changes and the need for dose adjustments. The objectives of this review are to summarize the evidence for change in perinatal pharmacokinetics of commonly used pharmacotherapies for mood disorders, discuss the implications for clinical and therapeutic drug monitoring (TDM), and make clinical recommendations.

METHODS

The English-language literature indexed on MEDLINE/PubMed was searched for original observational studies (controlled and uncontrolled, prospective and retrospective), case reports, and case series that evaluated or described pharmacokinetic changes or TDM during pregnancy or the postpartum period.

RESULTS

Pregnancy-associated changes in absorption, distribution, metabolism, and elimination may result in lowered psychotropic drug levels and possible treatment effects, particularly in late pregnancy. Mechanisms include changes in both phase 1 hepatic cytochrome P450 and phase 2 uridine diphosphate glucuronosyltransferase enzyme activities, changes in hepatic and renal blood flow, and glomerular filtration rate. Therapeutic drug monitoring, in combination with clinical monitoring, is indicated for tricyclic antidepressants and mood stabilizers during the perinatal period.

CONCLUSIONS

Substantial pharmacokinetic changes can occur during pregnancy in a number of commonly used antidepressants and mood stabilizers. Dose increases may be indicated for antidepressants including citalopram, clomipramine, imipramine, fluoxetine, fluvoxamine, nortriptyline, paroxetine, and sertraline, especially late in pregnancy. Antenatal dose increases may also be needed for lithium, lamotrigine, and valproic acid because of perinatal changes in metabolism. Close clinical monitoring of perinatal mood disorders and TDM of tricyclic antidepressants and mood stabilizers are recommended.

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.

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.

Newer anticonvulsants: lamotrigine, topiramate and gabapentin

BACKGROUND The second generation antiepileptic drugs (AEDs), which include lamotrigine, topiramate, and gabapentin, have been introduced during the past 20 years. Because the newer AEDs differ in their pharmacokinetics from the first generation AEDs, it is hoped that the second generation AEDs will be less teratogenic. METHODS The findings in pregnancy cohorts and case-control studies concerning lamotrigine, topiramate and gabapentin-exposed pregnancies have been analyzed. RESULTS The rate of all malformations in lamotrigine monotherapy-exposed pregnancies has been between 2.0 and 5.6%, in comparison to baseline rates of 1.1 to 3.6% in two unexposed comparison groups. Compared to reference populations, a higher risk (0.4%) of isolated oral clefts has been observed in one cohort of 1562 lamotrigine-exposed pregnancies, but the risk was lower (0.1%) in other studies. In topiramate-exposed pregnancies, the rate of all malformations has been 4.2 to 4.9%, with an increase in oral clefts with and without other anomalies. The limited information available now for gabapentin has shown no evidence of teratogenicity. Concerning other developmental effects of these drugs, young children exposed to lamotrigine in utero have shown no deficits in cognitive function. Prenatal exposure to topiramate has been associated with an elevated frequency of small size for gestational age newborns. CONCLUSIONS The information available suggests an increased risk of oral clefts in infants exposed to topiramate, and perhaps lamotrigine, early in pregnancy, and of growth retardation for topiramate-exposed infants. Larger sample sizes are needed to clarify the questions that have been raised.

Effect of pregnancy on topiramate pharmacokinetics in rabbits

Pregnancy is associated with various physiological changes that may lead to significant alterations in the pharmacokinetic profiles of many drugs. The present study was designed to investigate the potential effects of pregnancy on the pharmacokinetics of topiramate (TPM) in the rabbit model. Nineteen female New Zealand white rabbits (nine pregnant and 10 non-pregnant) were used in this study. Blood samples were collected from the animals just before receiving TPM orally at a dose of 20 mg/kg and then serially for up to 24 h. TPM plasma samples were analysed using a validated tandem mass spectrometric (LC-MS/MS) method. The mean values of TPM pharmacokinetic parameters (t(1/2), T(max), AUC(0-∞), and CL/F) were significantly modified in pregnant rabbits as compared with non-pregnant group. Pregnancy significantly (P < 0.05) increased TPM half-life (t(1/2)), time to attain the maximum plasma concentration (T(max)), and the area under TPM plasma concentration-time curve (AUC(0-∞)) and decreased the drug's oral clearance (CL/F) compared with non-pregnancy state in rabbits. The present study demonstrates that pregnancy alters the pharmacokinetics of TPM in rabbits in late gestational period and considerable inter-animal variability was observed. The findings of the present study indicate that TPM CL/F is decreased during late pregnancy in the rabbit model.

A comparison of the pharmacokinetics and pharmacodynamics of pregabalin and gabapentin

Pregabalin and gabapentin share a similar mechanism of action, inhibiting calcium influx and subsequent release of excitatory neurotransmitters; however, the compounds differ in their pharmacokinetic and pharmacodynamic characteristics. Gabapentin is absorbed slowly after oral administration, with maximum plasma concentrations attained within 3-4 hours. Orally administered gabapentin exhibits saturable absorption--a nonlinear (zero-order) process--making its pharmacokinetics less predictable. Plasma concentrations of gabapentin do not increase proportionally with increasing dose. In contrast, orally administered pregabalin is absorbed more rapidly, with maximum plasma concentrations attained within 1 hour. Absorption is linear (first order), with plasma concentrations increasing proportionately with increasing dose. The absolute bioavailability of gabapentin drops from 60% to 33% as the dosage increases from 900 to 3600 mg/day, while the absolute bioavailability of pregabalin remains at > or = 90% irrespective of the dosage. Both drugs can be given without regard to meals. Neither drug binds to plasma proteins. Neither drug is metabolized by nor inhibits hepatic enzymes that are responsible for the metabolism of other drugs. Both drugs are excreted renally, with elimination half-lives of approximately 6 hours. Pregabalin and gabapentin both show dose-response relationships in the treatment of postherpetic neuralgia and partial seizures. For neuropathic pain, a pregabalin dosage of 450 mg/day appears to reduce pain comparably to the predicted maximum effect of gabapentin. As an antiepileptic, pregabalin may be more effective than gabapentin, on the basis of the magnitude of the reduction in the seizure frequency. In conclusion, pregabalin appears to have some distinct pharmacokinetic advantages over gabapentin that may translate into an improved pharmacodynamic effect.

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.

Best practice in primary care pathology: review 12

This twelfth best practice review examines four series of common primary care questions in laboratory medicine: (i) antiepileptic drug monitoring; (ii) infectious diarrhoea; (iii) methicillin resistant Staphylococcus aureus; and (iv) brain natriuretic peptide. The review is presented in question–answer format, referenced for each question series. The recommendations represent a précis of guidance found using a standardised literature search of national and international guidance notes, consensus statements, health policy documents and evidence-based medicine reviews, supplemented by MEDLINE EMBASE searches to identify relevant primary research documents. They are not standards but form a guide to be set in the clinical context. Most are consensus rather than evidence-based. They will be updated periodically to take account of new information.

Epilepsy, sex hormones and antiepileptic drugs in female patients

Women with epilepsy have a higher incidence of reproductive endocrine disorders than the general female population. These alterations include polycystic ovary syndrome, hyperandrogenemia, infertility, hypothalamic amenorrhea and hyperprolactinemia. Reproductive dysfunction is attributed both to epilepsy itself and to antiepileptic drugs (AEDs). Focal epileptic discharges from the temporal lobe may have a direct influence on the function of the hypothalamic-pituitary axis, thus altering the release of sex steroid hormones, including the production of luteinizing hormone, follicle-stimulating hormone, gonadotropin-releasing hormone and prolactin. AEDs may modulate hormone release from the hypothalamic-pituitary-gonadal axis and they may alter the metabolism of sex hormones and their binding proteins. Hepatic enzyme-inducing AEDs, such as carbamazepine and phenytoin, may be most clearly linked to altered metabolism of sex steroid hormones, but valproic acid, an enzyme inhibitor, has also been associated with a frequent occurrence of polycystic ovary syndrome and hyperandrogenism in women with epilepsy. Therefore, treatment of epilepsy and selection of AEDs are important for reproductive health in female patients. The aim of the present review is to critically evaluate the recently published data concerning the interactions between sex hormones, epilepsy and AEDs.

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.

The management of epilepsy in pregnancy

While most women with epilepsy can expect a normal pregnancy outcome, epilepsy remains a significant contributor to both maternal and perinatal morbidity. Pre-pregnancy planning must address reliable contraception and optimisation of antiepileptic drug (AED) regimens to minimise teratogenic risk while maintaining seizure control. The most recent data from the AED registries regarding malformations is presented in this review, as is the limited data on the newer AEDs and studies linking neurocognitive outcomes to AED exposure. During pregnancy, important considerations include; therapeutic drug monitoring, surveillance for obstetric complications and vigilance for seizures during the intrapartum and postpartum period.

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.