MODEL-BASED LAMOTRIGINE CLEARANCE CHANGES DURING PREGNANCY: CLINICAL IMPLICATION

The risks associated with the use of lamotrigine during pregnancy

OBJECTIVE

This paper reviewed the relevant literature on the effects of lamotrigine on pregnancy outcomes to provide useful information regarding lamotrigine use in pregnant women with bipolar disorder.

METHODS

A systematic search of electronic databases and other original sources was conducted that examined the effects of lamotrigine on pregnancy outcomes.

RESULTS

It is not clear that foetuses of lamotrigine-exposed pregnant women are at higher risk of malformation or neurodevelopmental delay. When treating pregnant women with bipolar disorder, the risks associated with lamotrigine use have to be balanced with the risks of uncontrolled maternal symptoms. The information obtained from our review of psychotropic medications will assist clinicians in managing pregnant women with bipolar disorder.

CONCLUSIONS

Although lamotrigine has emerged as the safest mood stabiliser for use during pregnancy based on the clinical evidence thus far, further studies are needed to inform the best clinical practice when treating bipolar disorder in pregnant women.

Are doses of lamotrigine or levetiracetam adjusted during pregnancy?

Subtherapeutic levels of lamotrigine and levetiracetam are more likely to occur during pregnancy owing to the effect of pregnancy on their pharmacokinetics. This can lead to suboptimal control of epilepsy, and guidelines recommend proactive dose adjustment in the second and third trimesters alongside therapeutic drug monitoring (TDM). This retrospective cohort study using administrative databases aimed to investigate whether prescribers adjust the dose of lamotrigine or levetiracetam during and after pregnancy and whether TDM is used to manage dose adjustment. In 460 individual pregnancies, 232 women (61.4%) had their lamotrigine dose increased in the second and third trimesters and 44 women (53.7%) had their levetiracetam dose increased. Only 57 women (12.4%) had any TDM. The dose was not always decreased postpartum, and 157 women (56.9% of those who had escalated doses during pregnancy) had dose reduced following birth. Between 2012 and 2015, 29 women had an epilepsy-coded hospital discharge during pregnancy and were more likely to have had their dose of lamotrigine or levetiracetam increased. Overall, doses of lamotrigine and levetiracetam were not increased during pregnancy in 40% of the study population, dose changes were not often guided by TDM, and doses were not always reduced postpartum.

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.

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.

Pharmacokinetics of lamotrigine and its metabolite N-2-glucuronide: Influence of polymorphism of UDP-glucuronosyltransferases and drug transporters

AIMS

This study aimed to develop a population pharmacokinetic model for quantitative evaluation of the influence of genetic variants in metabolic enzymes and transporters on lamotrigine pharmacokinetics while taking into account the influence of various clinical, biochemical and demographic factors.

METHODS

We included 100 patients with epilepsy on stable dosing with lamotrigine as mono or adjunctive therapy. Lamotrigine and lamotrigine N-2-glucuronide concentrations were determined in up to two plasma samples per patient. Patients were genotyped for UGT1A4, UGT2B7, ABCB1 and SLC22A1. Population pharmacokinetic analysis was performed by non-linear mixed effects modelling. Prior knowledge from previous pharmacokinetic studies was incorporated to stabilize the modelling process. A parent-metabolite model was developed to get a more detailed view on the covariate effects on lamotrigine metabolism.

RESULTS

With a base model absorption rate (interindividual variability) was estimated at 1.96 h(-1) (72.8%), oral clearance at 2.32 l h(-1) (41.4%) and distribution volume at 77.6 l (30.2%). Lamotrigine clearance was associated with genetic factors, patient's weight, renal function, smoking and co-treatment with enzyme inducing or inhibiting drugs. In patients with UGT2B7-161TT genotype clearance was lower compared with GT and GG genotypes. Clearance was particularly high in patients with UGT2B7 372 GG genotype (compared with AA genotype it was 117%; 95% CI 44.8, 247% higher).

CONCLUSIONS

Variability in lamotrigine pharmacokinetics is large and quantification of its sources may lead to more precise individual treatment. Genotyping for UGT2B7 may be useful in various clinical settings.

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.

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

Over a million women with epilepsy are of childbearing age in the USA and require careful consideration of not only type of antiepileptic drug (AED) but also dosage, in the event of a planned or unplanned pregnancy. Careful selection of AEDs can lower the potential adverse effects of AEDs while maintaining seizure control for the health of not only on the patient, the mother, but also the unborn fetus. The number of treatment options has increased significantly in the last 20 years and remarkable progress has been made in characterizing the risks AEDs pose to pregnant women and fetuses. There are now robust data on teratogenesis, a growing body of data on neonatal/obstetrical outcomes and on neurodevelopmental problems associated with each AED, and some data about seizure control during pregnancy. Based on clinical evidence so far, levetiracetam and lamotrigine have emerged as the safest during pregnancy, although others may also be suitable. Despite being a common belief, not all polytherapy combinations may be detrimental, especially when avoiding valproate and topiramate. Here, we review the available clinical research, highlighting recent findings and provide thoughts for future directions in the field.

Mood stabilizers in pregnancy and lactation

Management of bipolar during pregnancy and postpartum is very challenging. The treating clinicians have to take into account various factors like current mental state, longitudinal history of the patient, past history of relapse while off medication, response to medication, time of pregnancy at which patient presents to the clinician, etc. The choice of drug should depend on the balance between safety and efficacy profile. Whenever patient is on psychotropic medication, close and intensive monitoring should be done. Among the various mood stabilizers, use of lithium during the second and third trimester appears to be safe. Use of valproate during first trimester is associated with major malformation and long-term sequalae in the form of developmental delay, lower intelligence quotient, and higher risk of development of autism spectrum disorder. Similarly use of carbamazepine in first trimester is associated with higher risk of major congenital malformation and its use in first trimester is contraindicated. Data for lamotrigine (LTG) appears to be more favorable than other antiepileptics. During lactation, use of valproate and LTG is reported to be safe. Use of typical and/atypical antipsychotic is a good option during pregnancy in women with bipolar disorder.

Epilepsy (generalised seizures)

INTRODUCTION

About 3% of people will be diagnosed with epilepsy during their lifetime, but about 70% of people with epilepsy eventually go into remission.

METHODS AND OUTCOMES

We conducted a systematic review and aimed to answer the following clinical question: What are the effects of additional treatments in people with drug-resistant epilepsy characterised by generalised seizures? We searched: Medline, Embase, The Cochrane Library, and other important databases up to April 2014 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).

RESULTS

We found four studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.

CONCLUSIONS

In this systematic review we present information relating to the effectiveness and safety on the addition of the following interventions: lacosamide, lamotrigine, levetiracetam, perampanel, and zonisamide versus the addition of placebo.

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.