Lamotrigine in pregnancy: clearance, therapeutic drug monitoring, and seizure frequency

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.

Pregnancy and epilepsy management and outcome: an update

Epilepsy affects one in 100 individuals. Although epilepsy is gender neutral, women face more challenges with regard to treatment than men. Treatment of women with epilepsy is a therapeutic challenge since they are unlikely to be medication free. An estimated 1 million women with epilepsy are of childbearing age. Each year, approximately 20,000 births occur in women with epilepsy. Despite these challenges, over 90% of women with epilepsy have normal healthy outcomes. Ensuring seizure control is of utmost importance to the health of the mother and fetus. Serum concentrations of antiepileptic drug (AED) decrease during pregnancy resulting in an increased risk of seizure activity, which may result in serious consequences such as maternal injury or fetal and/or maternal demise. Teratogenicity secondary to AED drug exposure has long been reported, especially with the older AEDs, and to some degree with newer agents. More recently, the discovery of long-term cognitive impairment has been reported in offspring exposed to valproate in utero. Choice of AED must balance seizure control with minimizing the risk of malformations and other health issues. Prenatal planning is warranted whenever possible in order to address these concerns. Supplementation with folic acid pregestationally may be helpful in preventing malformations such as spina bifida.

Hormonal aspects of epilepsy

The relationships among hormones, epilepsy, and the medications used to treat epilepsy are complex, with tridirectional interactions that affect both men and women in various ways. Abnormalities of baseline endocrine status occur more commonly in people with epilepsy. Abnormalities are most often described for the sex steroid hormone axis, commonly presenting as sexual dysfunction in men and women with epilepsy and lower fertility. Other signs and symptoms in women with epilepsy include menstrual irregularities, premature menopause, and polycystic ovarian syndrome. The evaluation and care of adult patients with epilepsy should include considerations of the common hormonal aberrations that occur in this patient population. Questions about reproductive health disorders, sexual function, symptoms of thyroid disorders, and bone health should be part of the evaluation of all adult patients with epilepsy. Further laboratory or radiologic testing and referral to other specialists to participate in collaborative care may be warranted if underlying disorders are suspected, especially given that many of these hormone abnormalities can result in long-term health risks as well as negatively affect quality of life. AEDs and hormones have a bidirectional interaction that can impair the efficacy of contraceptive hormone treatments and of the AEDs. Endogenous hormones can influence seizure severity and frequency, resulting in catamenial patterns of epilepsy. However, this susceptibility to hormonal influences can be used to develop hormonal strategies to improve seizure control in women with epilepsy with use of cyclic PROG supplementation or alteration of the endogenous hormone release. Additionally, development of the neurosteroid analog ganaxolone provides a novel approach that can potentially be used across both genders and all age groups.

Postpartum depression in women with epilepsy: influence of antiepileptic drugs in a prospective study

Patients with epilepsy are at high risk for major depressive disorder (MDD) and, according to one report, postpartum depression (PPD) as well. The study described here sought to determine the prevalence and risk factors for PPD among women with epilepsy. Fifty-six women with epilepsy participating in a prospective study of perinatal antiepileptic drug (AED) pharmacokinetics were included. Participants completed the Beck Depression Inventory (BDI) during pregnancy and the postpartum period. Fourteen participants (25.0%) had a postnatal BDI score > or =12 indicative of PPD. Logistic regression indicated that significant risk factors for PPD among women with epilepsy included multiparity (odds ratio=12.5) and AED polytherapy (odds ratio=9.3). The rate of PPD was unaffected by the use of specific AEDs. In conclusion, PPD rates are higher among women with epilepsy than the general population, particularly those who are multiparous or receiving AED polytherapy, and there is no evidence that AED selection modifies this risk.

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.

Up-regulation of UDP-glucuronosyltransferase (UGT) 1A4 by 17beta-estradiol: a potential mechanism of increased lamotrigine elimination in pregnancy

Oral clearance of lamotrigine, an antiepileptic drug commonly used in pregnant women, is increased in pregnancy by unknown mechanisms. In this study, we show that 17beta-estradiol (E(2)) up-regulates expression of UDP glucuronosyltransferase (UGT) 1A4, the major enzyme responsible for elimination of lamotrigine. Endogenous mRNA expression levels of UGT1A4 in estrogen receptor (ER) alpha-negative HepG2 cells were induced 2.3-fold by E(2) treatment in the presence of ER alpha expression. E(2) enhanced transcriptional activity of UGT1A4 in a concentration-dependent manner in HepG2 cells when ER alpha was cotransfected. Induction of UGT1A4 transcriptional activity by E(2) was also observed in ER alpha-positive MCF7 cells, which was abrogated by pretreatment with the antiestrogen fulvestrant (ICI 182,780). Analysis of UGT1A4 upstream regions using luciferase reporter assays identified a putative specificity protein-1 (Sp1) binding site (-1906 to -1901 base pairs) that is critical for the induction of UGT1A4 transcriptional activity by E(2). Deletion of the Sp1 binding sequence abolished the UGT1A4 up-regulation by E(2), and Sp1 bound to the putative Sp1 binding site as determined by a electrophoretic mobility shift assay. Analysis of ER alpha domains using ER alpha mutants revealed that the activation function (AF) 1 and AF2 domains but not the DNA binding domain of ER alpha are required for UGT1A4 induction by E(2) in HepG2 cells. Finally, E(2) treatment increased lamotrigine glucuronidation in ER alpha-transfected HepG2 cells. Together, our data indicate that up-regulation of UGT1A4 expression by E(2) is mediated by both ER alpha and Sp1 and is a potential mechanism contributing to the enhanced elimination of lamotrigine in pregnancy.

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.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

RECOMMENDATIONS

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

Seizure frequency in pregnant women treated with lamotrigine monotherapy

Previous studies have demonstrated that the pharmacokinetics of the new antiepileptic drug (AED) lamotrigine (LTG) are substantially influenced by pregnancy and are more likely to be associated with seizure deterioration in pregnancy compared to other AEDs. This is of great concern, as LTG has developed into a first-line AED for women of childbearing age. In this study we evaluated the risk of seizure deterioration in a cohort of women treated with LTG monotherapy (n = 42) who were closely monitored with frequent dose adjustments based on monthly routine plasma level determinations. It was demonstrated that with this close monitoring set-up, the risk of increased seizure frequency (19%) was not higher than that reported for other AED treatment regimens.

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.

Does increased levetiracetam clearance during pregnancy require planned intervention?

Pharmacokinetics of Levetiracetam During Pregnancy, Delivery, in the Neonatal Period, and Lactation. Tomson T, Palm R, Källén K, Ben-Menachem E, Söderfeldt B, Danielsson B, Johansson R, Luef G, Ohman I. Epilepsia 2007;48:1111–1116. PURPOSE: To study pharmacokinetics of levetiracetam (LEV) during pregnancy, delivery, lactation, and in the neonatal period. METHODS: Fourteen women with epilepsy receiving LEV treatment during pregnancy and lactation contributed with 15 pregnancies to this prospective study in which LEV concentrations in plasma and breast milk were determined. Trough maternal plasma samples were collected each trimester, and at baseline after delivery. Blood samples were obtained at delivery from mothers, from the umbilical cord, and from newborns during 2 days after delivery. LEV concentration was also determined in breast milk and in plasma collected from 11 of the mothers and their suckling infants after birth. RESULTS: The umbilical cord/maternal plasma concentration ratios ranged from 0.56 to 2.0 (mean 1.15, n = 13). LEV plasma concentrations in the neonates declined with an estimated half-life of 18 h (n = 13). The mean milk/maternal plasma concentration ratio was 1.05 (range, 0.78–1.55, n = 11). The infant dose of LEV was estimated to 2.4 mg/kg/day, equivalent to 7.9% of the weight-normalized maternal dose. Plasma concentrations in breastfed were approximately 13% of the mother's plasma levels. Maternal plasma concentrations during third trimester were only 40% of baseline concentrations outside pregnancy (p < 0.001, n = 7). CONCLUSIONS: Our observations suggest considerable transplacental transport of LEV and fairly slow elimination in the neonate. Plasma concentrations of LEV in nursed infants are low despite an extensive transfer of LEV into breast milk. Pregnancy appears to enhance the elimination of LEV resulting in marked decline in plasma concentration, which suggests that therapeutic monitoring may be of value.

Hormones, seizures, and lamotrigine: Oh, my!

Oral Contraceptives Induce Lamotrigine Metabolism: Evidence from a Double-Blind, Placebo-Controlled Trial. Christensen J, Petrenaite V, Atterman J, Sidenius P, Öhman I, Tomson T, Sabers A. Epilepsia 2007;48(3):484–489.

Purpose

This study evaluates the effect of oral contraceptives on lamotrigine (LTG) plasma concentrations and urine excretion of LTG metabolites in a double-blind, placebo-controlled, crossover study in patients with epilepsy.

Methods

Women with epilepsy, treated with LTG in monotherapy and taking combination-type oral contraceptives, were randomized to treatment with placebo or a standard combination-type contraceptive pill. The dose-corrected trough plasma concentration of LTG and the ratio of N-2-glucuronide/unchanged LTG on urine after 21 days of concomitant placebo treatment was analyzed versus those after 21 days of concomitant treatment with the oral contraceptive pill.

Results

The mean dose-corrected LTG concentration after placebo treatment was 84% [95% confidence interval (CI), 45–134%] higher than after oral contraceptives, signifying an almost doubling of the concentration after cessation of oral contraceptives. Most of this increase took place within the first week after oral contraceptives were stopped. The N-2-glucuronide/LTG ratio in the urine was decreased by 31% (95% CI, −20–61%) when shifting from oral contraceptives to placebo.

Conclusions

Cessation of oral contraceptives leads to an 84% increase in the concentration of LTG. In parallel, the excretion of the N-2-glucuronide was decreased, indicating that the changes are caused by altered LTG glucuronidation. The change in LTG concentrations was observed within 1 week of the shift of treatment, suggesting that induction and deinduction of LTG glucuronidation is faster than that seen for other metabolic pathways (e.g., cytochrome P450).

Antiepileptic drug therapy in pregnancy I: gestation-induced effects on AED pharmacokinetics

The ideal management of women with epilepsy during pregnancy involves achieving an optimal balance between minimizing fetal exposure to the deleterious influences of both antiepileptic drugs (AEDs) and of seizures. Women with increased seizures during pregnancy tend to have subtherapeutic AED concentrations. Multiple physiological changes during pregnancy influence drug disposition, including increased volume of distribution, increased renal elimination, altered hepatic enzyme activity, and a decline in plasma protein concentrations. Many of the AEDs are characterized by significant increases in clearance during pregnancy. Studies performed thus far provide convincing findings for significant increases in the clearance of lamotrigine and phenytoin during pregnancy; other studies support that phenobarbital, oxcarbazepine, and levetiracetam clearances also most likely increase during pregnancy. Therapeutic drug monitoring of lamotrigine with adjustment of dosages during pregnancy to maintain that individual's target concentration has been shown to decrease the risk for increased seizure frequency. Reports of seizure worsening with decreased concentrations of other AEDs have been reported but not studied in similar formal protocols. Future studies of formal pharmacokinetic modeling of AEDs during pregnancy, with assessment of maternal and fetal/newborn consequences, could provide an important step toward achieving effective drug dosing to maintain therapeutic objectives for the mother but at the same time minimize fetal drug exposure.

Pharmacology of antiepileptic drugs during pregnancy and lactation

Most women with epilepsy require continuous treatment during pregnancy, making antiepileptic drugs (AEDs) one of the most frequent chronic teratogen exposures. Therapeutic decisions should balance the risks to the developing fetus of AED exposure and of not treating or undertreating the epilepsy. The International AED Pharmacology Work Group of the Health Outcomes in Pregnancy and Epilepsy (HOPE) Forum identified four pharmacology topics critical to enhancing maternal and fetal outcomes for pregnancies exposed to AEDs: (1) hormonal therapies and endogenous changes: bidirectional interactions with AEDs; (2) pharmacokinetic alterations during pregnancy, the role of therapeutic drug monitoring, and the influence on seizure control and maternal and fetal outcomes; (3) multidrug transporters and their various roles during pregnancy; (4) breastfeeding in mothers taking AEDs. The report provides an overview of these key topics, highlights gaps in the current knowledge, and provides future directions for needed research.