Serum concentration/dose ratio of levetiracetam before, during and after pregnancy

The impact of pregnancy on the pharmacokinetics of antiseizure medications: A systematic review and meta-analysis of data from 674 pregnancies

OBJECTIVE

Increasing evidence suggests that the physiological changes of pregnancy may impact pharmacokinetics of antiseizure medications (ASM), and this may affect treatment outcomes. The aim of this study was to quantify the pregnancy impact on the ASM pharmacokinetics.

METHODS

A systematic literature search was conducted in PubMed/EMBASE in November 2022 and updated in August 2023 for studies comparing levels of ASM in the same individuals during pregnancy and in the preconception/postpartum period. Alteration ratios between the 3rd trimester and baseline were estimated. We also performed a random-effects meta-analysis calculating between-timepoint differences in mean differences (MDs) and 95% confidence intervals (95%CIs) for dose-adjusted plasma concentrations (C/D ratios). Study quality was assessed using the ClinPK guidelines.

RESULTS

A total of 65 studies investigating 15 ASMs in 674 pregnancies were included. The largest differences were reported for lamotrigine, oxcarbazepine and levetiracetam (alteration ratio 0.42, range 0.07-2.45, 0.42, range 0.08-0.82 and 0.52, range 0.04-2.77 respectively): accordingly, C/D levels were lower in the 3rd trimester for lamotrigine, levetiracetam and the main oxcarbazepine metabolite monohydroxycarbazepine (MD = -12.33 × 10-3, 95%CI = -16.08 to -8.58 × 10-3 (μg/mL)/(mg/day), p < 0.001, MD = -7.16 (μg/mL)/(mg/day), 95%CI = -9.96 to -4.36, p < 0.001, and MD = -4.87 (μg/mL)/(mg/day), 95%CI = -9.39 to -0.35, p = 0.035, respectively), but not for oxcarbazepine (MD = 1.16 × 10-3 (μg/mL)/(mg/day), 95%CI = -2.55 to 0.24 × 10-3, p = 0.10). The quality of studies was acceptable with an average rating score of 11.5.

CONCLUSIONS

Data for lamotrigine, oxcarbazepine (and monohydroxycarbazepine) and levetiracetam demonstrate major changes in pharmacokinetics during pregnancy, suggesting the importance of therapeutic drug monitoring to assist clinicians in optimizing treatment outcomes.

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

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

Adaptive Dosage Strategy of Levetiracetam in Chinese Epileptic Patients: Focus on Pregnant Women

There is presently no efficient dose individualization strategy for the use of antiseizure medications in epileptic pregnant patients. This study aimed to develop a population pharmacokinetics model for levetiracetam and propose a tailored adaptive individualized dosage strategy for epileptic pregnant patients. A total of 322 levetiracetam plasma concentrations from 238 patients with epilepsy were included, including 216 women with epilepsy (20.83% of whom were pregnant). The levetiracetam plasma concentration was measured using a validated ultra-performance liquid chromatography-tandem mass spectrometry assay, and the data were modeled using a nonlinear mixed-effects model. The resultant model served as the basis for simulating the dosage adjustment strategy. A one-compartment model with first-order elimination best described the pharmacokinetic data of levetiracetam. The apparent clearance (CL/F) was 3.43 L/h (95% CI 3.30-3.56) and the apparent volume of distribution was 43.7 L (95% CI 40.4-47.0) for a typical individual of 57.2 kg. Pregnancy and body weight were found to be significant covariates of CL/F of levetiracetam. The recommended regimen of levetiracetam could be predicted by the population pharmacokinetic model based on body weight, gestational age, and the daily dose of levetiracetam taken before pregnancy.

Therapeutic drug monitoring in pregnancy: Levetiracetam

OBJECTIVE

Levetiracetam (LEV) is an antiseizure medication that is mainly excreted by the kidneys. Due to its low teratogenic risk, LEV is frequently prescribed for women with epilepsy (WWE). Physiological changes during gestation affect the pharmacokinetic characteristics of LEV. The goal of our study was to characterize the changes in LEV clearance during pregnancy and the postpartum period, to better plan an LEV dosing paradigm for pregnant women.

METHODS

This retrospective observational study incorporated a cohort of women who were followed up at the epilepsy in pregnancy clinic at Tel Aviv Sourasky Medical Center during the years 2020-2023. Individualized target concentrations of LEV and an empirical postpartum taper were used for seizure control and to reduce toxicity likelihood. Patient visits took place every 1-2 months and included a review of medication dosage, trough LEV blood levels, week of gestation and LEV dose at the time of level measurement, and seizure diaries. Total LEV concentration/dose was calculated based on LEV levels and dose as an estimation of LEV clearance.

RESULTS

A total of 263 samples were collected from 38 pregnant patients. We observed a decrease in LEV concentration/dose (C/D) as the pregnancy progressed, followed by an abrupt postpartum increase. Compared to the 3rd trimester, the most significant C/D decrease was observed at the 1st trimester (slope = .85), with no significant change in the 2nd trimester (slope = .11). A significant increase in C/D occurred postpartum (slope = 5.23). LEV dose was gradually increased by 75% during pregnancy compared to preconception. Average serum levels (μg/mL) decreased during pregnancy. During the postpartum period, serum levels increased, whereas the LEV dose was decreased by 24%, compared to the 3rd trimester.

SIGNIFICANCE

LEV serum level monitoring is essential for WWE prior to and during pregnancy as well as postpartum. Our data contribute to determining a rational treatment and dosing paradigm for LEV use during both pregnancy and the postpartum period.

Therapeutic Drug Monitoring of Levetiracetam in Different Trimesters of Pregnant Women with Epilepsy in a Tertiary Care Center: A Prospective Study

BACKGROUND

Levetiracetam is the most commonly used antiepileptic drug in pregnant women due to its low teratogenic risk profile, favorable pharmacokinetic characteristics, and safety profile. Serum levels of levetiracetam vary in epilepsy during pregnancy. Therefore, the aim of the study was to evaluate the serum levels of levetiracetam during different trimesters of pregnancy by using therapeutic drug monitoring (TDM).

MATERIALS AND METHODS

This was a single-center, prospective study. Pregnant women with epilepsy on levetiracetam were enrolled after getting written informed consent from them. Serum trough levels of levetiracetam were estimated at all trimesters by high-performance liquid chromatography (HPLC).

RESULTS

The study included 16 participants with mean ± standard deviation (SD) age of 27.75 ± 4 years. There were nine (56.2%) participants with generalized seizure disorder and seven (43.8%) participants of focal seizure disorder. Among 16 patients, 10 (62.5%) participants were on levetiracetam alone and six (37.5%) participants were on levetiracetam combined with other antiepileptic drugs. In a total of 48 trough samples, 45 sample concentrations were below the therapeutic range of 12-46 mg/l and three sample concentrations were within the therapeutic range. There was a statistically significant difference in the concentration-dose ratio (CDR) of levetiracetam between the third and first trimesters (P-value 0.018).

CONCLUSION

There was a statistically significant difference in serum levetiracetam concentration between the third and first trimesters. A well-conducted, intensive pharmacokinetic sampling study in PWWE with a control group is needed in future to evaluate the whole pharmacokinetic profile of levetiracetam and to correlate the clinical outcome.

Managing Antiseizure Medications in Pregnancy: Is Earlier and More Frequent Monitoring Better?

Background and Objective

Medication management in pregnant women with epilepsy (PWWE) poses challenges, and understanding the effects of metabolic changes on antiseizure medications (ASMs) is important in planning care for PWWE. The possible teratogenic effects and risks of poorly controlled seizures have to be weighed. There are data in the literature on clinical management of ASMs including the effects of drug levels on seizures and factors that predict seizure frequency, but timing and frequency of monitoring and dose adjustment paradigms have not been well studied.

Methods

This retrospective study was approved by the Institutional Review Board at Johns Hopkins University. We retrospectively identified adult PWWE evaluated during pregnancy at the Johns Hopkins Bayview Medical Center epilepsy clinic, between January 1, 2007, and January 1, 2021. We reviewed charts for information regarding demographics, medical and epilepsy history, medications, serum drug levels, and dosing paradigms. We assessed risk factors for breakthrough seizures with a focus on frequency and timing of laboratory testing. We calculated the dose-normalized concentration (DNC) for analysis with levetiracetam and lamotrigine, assessing changes in DNC over time by half trimesters, and analyzed DNC and effects on seizures in pregnancy. We also compared preemptive vs clinically based lamotrigine dose adjustments in managing epilepsy in pregnancy.

Results

A total of 45 pregnancies in 39 patients were included in this study, 8 generalized, 28 focal epilepsy, and 3 unclassified. 31 PWWE (36 pregnancies) were on lamotrigine and/or levetiracetam, and 14 of these pregnancies experienced breakthrough seizures, 77% in the first trimester. Seizures led to the diagnosis of pregnancy in 5 patients. The DNC for levetiracetam decreased significantly compared with prepregnancy levels by the second half of the first trimester and demonstrated variable but frequently significant or near significant reduction throughout pregnancy. DNC for lamotrigine decreased significantly in the first half of the first trimester and remained significant throughout pregnancy. Age of mother at conception, week of first ASM serum level and number of levels obtained during pregnancy, and epilepsy type were not associated with breakthrough/increase in seizures. The history of drug resistance (p = 0.038) was associated with a higher odds of seizures. In those on lamotrigine, preemptive dose adjustments demonstrated similar results regarding seizure control when compared with clinical-based or laboratory-based dose management (p = 0.531).

Discussion

This study demonstrates that frequency and timing of ASM level monitoring may not affect overall seizure outcomes during pregnancy in those on lamotrigine or levetiracetam. Furthermore, one can consider preemptive dose adjustments or a laboratory-based/clinical-based approach in managing lamotrigine as both seem safe and feasible. However, in those with drug-resistant epilepsy before pregnancy, earlier and closer monitoring is warranted given the risk of seizures early during pregnancy. Larger prospective studies are needed to confirm these results.

Application of PBPK modeling in predicting maternal and fetal pharmacokinetics of levetiracetam during pregnancy

Levetiracetam is currently being used to treat epilepsy in pregnant women. The plasma concentration of levetiracetam drops sharply during pregnancy, and the inability of pregnant women to maintain therapeutic concentrations can lead to seizures. This study aimed to predict the changes in fetal and maternal plasma exposure to levetiracetam during pregnancy and provide advice on dose adjustment. The physiology-based pharmacokinetics (PBPK) model was developed using PK-Sim and Mobi software, and validated following comparison of the observed plasma concentration and pharmacokinetic parameters. The levetiracetam PBPK model for mother and the fetus at various stages of pregnancy was successfully established and verified. Predictions indicated that the area under the steady-state concentration-time curve for levetiracetam decreased to 83, 62, and 67% of baseline values in the first, second, and third trimesters, respectively. Based on PBPK predictions, the recommended dose of levetiracetam is 1.2, 1.6, and 1.5 times the baseline dose in the first, second, and third trimesters, respectively, not exceeding 4000 mg/day in the third trimester due to fetal safety. The levetiracetam PBPK model for pregnancy was successfully developed and validated, and could provide alternative levetiracetam dosing regimens across the stages of pregnancy.

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.

Seizure Deterioration with Increased Levetiracetam Blood Concentration during the Postpartum Period in Refractory Temporal Lobe Epilepsy

We evaluated a 39-year-old pregnant woman with right temporal lobe epilepsy. During the second trimester, seizure deterioration was responsive to an increased daily dose of levetiracetam (LEV). However, immediately after delivery, new non-habitual seizures emerged along with a sharply increased LEV concentration. The frequency of habitual seizures also slightly increased. The non-habitual seizures completely disappeared, and the frequency of the habitual seizures improved to the baseline level after the LEV dosage was reduced. Thus, a paradoxical effect of an increased LEV blood concentration was assumed to be a potential cause of these events. Peripartum pharmacokinetic fluctuations in LEV levels should be monitored carefully.

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

IMPORTANCE

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

OBJECTIVE

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

DESIGN, SETTING, AND PARTICIPANTS

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

EXPOSURE

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

MAIN OUTCOMES AND MEASURES

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

RESULTS

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

CONCLUSIONS AND RELEVANCE

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

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.

Correlation of elevated lamotrigine and levetiracetam serum/plasma levels with toxicity: A long-term retrospective review at an academic medical center

Lamotrigine and levetiracetam are widely used second-generation anti-epileptic drugs. Existing literature indicates that overdose of either drug is typically benign, but neurologic and cardiac toxicity can occur in some cases. In this retrospective study, we analyzed a large dataset of serum/plasma drug levels for lamotrigine and levetiracetam. The data covered 1,930 unique patients (5,046 levels) for lamotrigine and 2,451 patients (4,359 levels) for levetiracetam. We performed detailed chart review on all patients with one or more lamotrigine levels greater than 14.0 mg/L (293 unique patients) and all patients with one or more levetiracetam levels of 80 mg/L or higher (106 unique patients). No deaths directly attributable to lamotrigine or levetiracetam toxicity were reported. For cases with lamotrigine levels greater than 14.0 mg/L, the majority of patients were asymptomatic (55.3 %, n = 162). The most common presenting symptoms were ataxia (14.3 %, n = 42), seizures (14.0 %, n = 41), dizziness (11.9 %, n = 35), and altered mental status (11.6 %, n = 34). There were 12 overdoses (11 intentional) involving lamotrigine, all of which presented with either altered mental status (n = 8) or seizures (n = 4). The highest estimated dose reportedly ingested was 20 g. Cardiac toxicity was observed in two cases involving intentional overdose of lamotrigine. For patients with levetiracetam serum/plasma levels of 80 mg/L or higher, 48 patients (45.3 %) were asymptomatic. Symptomatic patients most commonly presented with seizures (31.1 %, n = 33) and altered mental status (15.1 %, n = 16), and none showed cardiac symptoms. There were only two cases involving intentional levetiracetam overdose, one of which presented with altered mental status after ingestion of 45 g and the other asymptomatic after ingestion of 6 g. Overall, our data is consistent with previous investigations that lamotrigine and levetiracetam toxicity most typically presents with neurologic symptoms and rarely cardiac arrhythmias. Approximately half of the patients with elevated lamotrigine or levetiracetam drug levels are asymptomatic.

Levetiracetam in lactation: How much is excreted into human breast milk?

AIMS

In breastfeeding women, anti-epileptic therapy can lead to infant toxicities, even with newer anti-epileptic drugs such as levetiracetam. This study assessed levetiracetam breastmilk excretion and its correlation with the maternal oral dose and serum concentrations.

METHODS

Women with epilepsy treated with levetiracetam were recruited to this study and completed a questionnaire. Levetiracetam concentrations were determined in serial breastmilk samples (pre-dose to 12 h post-dose period) and in a single pre-dose maternal serum sample.

RESULTS

Twenty breastfeeding women and 21 infants (one woman with twins; 16 fully and five partially breastfed infants) participated in this study. The trough breastmilk/serum ratio of levetiracetam was 0.98 ± 0.20. The infant levetiracetam daily dose was 5.39 ± 1.96 and 2.70 ± 0.98 mg^. kg^-1. d^-1 , and the relative infant dose (RID) was 13.8 ± 3.1% and 6.9 ± 1.6% in the fully and partially breastfed infants, respectively. Substantial correlations between the levetiracetam dose, maternal serum and breastmilk trough concentrations, and breastmilk AUC values were found. Three women reported somnolence in their fully breastfed infants, which resolved shortly after switching to partial breastfeeding. All the infants gained weight according to their age.

CONCLUSIONS

Infant levetiracetam exposure via the breastmilk was close to the safety thresholds (trough breastmilk/serum ratio slightly below 1, RID > 10% in fully breastfed infants), and infant somnolescence reports could be related to exposure of the infants to levetiracetam via breastmilk. Further studies are warranted to reveal the short- and long-term safety of levetiracetam in breastfeeding.

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.

Therapeutic Drug Monitoring in Pregnant Patients

During pregnancy, there are several physiological changes during each trimester that can affect the absorption, distribution, metabolism, and elimination of drugs. Although there is a potential need to understand the pharmacokinetics and pharmacodynamics of drugs in pregnant patients, therapeutic drug monitoring is not well established for various drug classes due to ethical and safety concerns regarding the neonate. Potential risks from in utero drug exposure to the fetus may impact growth and development and may cause malformations or teratogenesis. The clinician must consider the benefits of drug treatment for the pregnant mother versus the risk to the fetus, before prescribing medications during pregnancy. The objective of this review is to aid clinicians, pharmacists, and laboratorians in understanding the pharmacokinetic and pharmacodynamic changes during pregnancy, to provide drug class recommendations for monitoring therapy throughout pregnancy via therapeutic drug monitoring, and to highlight the recent directives of governing agencies on maternal and fetal health.

Umbilical Cord, Maternal Milk, and Breastfed Infant Levetiracetam Concentrations Monitoring at Delivery and during Early Postpartum Period

(1) To obtain objective information about levetiracetam transplacental passage and its transport into colostrum, mature milk, and breastfed infants, we analyzed data from women treated for epilepsy between October 2006 and January 2021; (2) in this cohort study, maternal, umbilical cord, milk, and infant serum concentrations were measured at delivery, 2-4 days postpartum (colostrum) and 7-31 days postpartum (mature milk). Paired umbilical cord serum, maternal serum, breastfed infant serum, and milk concentrations were used to assess the ratios of umbilical cord/maternal serum, milk/maternal serum, and infant/maternal serum concentrations. The influence of combined treatment with enzyme-inducing antiseizure medication carbamazepine was assessed; (3) the umbilical cord/maternal serum concentration ratio ranged between 0.75 and 1.78 (mean 1.10 ± 0.33), paired maternal and umbilical cord serum concentrations were not significantly different, and a highly significant correlation was found between both concentrations. The mean milk/maternal serum concentration ratio was 1.14 ± 0.27 (2-4 days postpartum) and 1.04 ± 0.24 (7-31 days postpartum) while the mean infant/maternal serum concentration ratio was markedly lower (0.19 ± 0.13 and 0.14 ± 0.05, respectively); (4) levetiracetam was found in the umbilical cord at a concentration similar to those in maternal serum. All of the breastfed infant serum concentrations were below the reference range used for the general epileptic population.

Population Pharmacokinetics and Dosing Recommendations of Levetiracetam in Adult and Elderly Patients With Epilepsy

The objective was to develop and externally validate a population pharmacokinetic model of levetiracetam in adult and elderly patients with epilepsy, and to perform dosing simulations to propose individualized dosing regimens more likely to achieve therapeutic concentrations. This prospective study included 367 plasma samples from 107 patients receiving oral levetiracetam. Samples were analyzed by HPLC-UV. Pharmacokinetic data, as well as patient demographic, clinical characteristics, other drug therapy, and the use of innovator or generic products of levetiracetam, were collected. Population modeling was performed with NONMEM and included internal and external validations of the final model. Simulations were used to propose optimized dosing regimens. The pharmacokinetics of levetiracetam was described by a one-compartment model with first-order absorption and linear elimination. Body surface area had a significant effect on the apparent volume of distribution, as did creatinine clearance (CrCL) over the drug clearance (p < 0.01). The final model performed adequately during external validation testing. The final model showed a better predictive performance. Dosing simulations support 1000 mg 12-hourly dosing of levetiracetam for patients with CrCL ~60-75 mL/min with higher dose needed for higher values (1500 mg 12-hourly for CrCL ~93-111 mL/min). Dosing regimens should be personalized to the patient's CrCL to maximize the likelihood of therapeutic concentrations.

Therapeutic levetiracetam monitoring during pregnancy: "mind the gap"

Background

Epilepsy is one of the most common chronic neurological conditions and its treatment during pregnancy is challenging. Levetiracetam (LEV) is an antiepileptic medication frequently used during pregnancy. Only a few small studies have been published on LEV monitoring during pregnancy, demonstrating decreased serum LEV levels during the first and second trimester; however, the most significant decrease was observed during the third trimester of pregnancy. In this study we aimed to evaluate LEV pharmacokinetics during different stages of pregnancy.

Methods

We followed up and monitored serum levels of pregnant women treated with LEV for epilepsy.

Results

Fifty-nine women with 66 pregnancies during the study period were included. The lowest raw LEV serum concentrations were observed during the first trimester. Compared with the pre-pregnancy period, raw serum concentration was lower by 5.76 mg/L [95% confidence interval (CI) (2.78, 8.75), p = 0.039] during the first trimester. Comparing the decrease in the first trimester with either the second or the third, no significant changes were observed (p = 0.945, p = 0.866). Compared with pre-pregnancy measurements, apparent clearance was increased by 71.08 L/day [95%CI (16.34, 125.83), p = 0.011] during the first trimester. About 30% of LEV serum levels during pregnancy were below the laboratory quoted reference range.

Conclusions

Raw LEV serum levels tend to decrease during pregnancy, mainly during the first trimester contrary to previous reports. Monitoring of LEV serum levels is essential upon planning pregnancy and thereafter if pre-pregnancy LEV levels are to be maintained. However, more studies are needed to assess the correlation with clinical outcome.

Collaboration of Care for Women with Epilepsy in their Reproductive Years

Over half a million women of childbearing age have epilepsy, many of which will require family planning care at some point in their reproductive years. Matters relating to contraception, pregnancy, fertility, and sexual functioning are all impacted to varying degrees by the use of antiepileptic drugs (AEDs) to treat epilepsy and require active management by a woman's neurologist. It is important that a woman's obstetrician/gynecologist (OBGYN) and internist are aware of the way in which their care may be related to her epilepsy care and how this can be successfully comanaged with her neurologist. This includes the impact AED therapies have on pregnancy, such as risk of teratogenicity, changes to AED clearance rates during pregnancy and postpartum, and risk of seizure worsening while pregnant; interactions of hormonal contraceptives and AEDs; side effects of AED treatment on hormonal systems and sexual functioning; and matters of fertility and infertility treatments. The current editorial discusses these relationships between AED choice, dose, and family planning matters for women with epilepsy in their childbearing years to support the collaboration of care between her neurologist, OBGYN, and internist.

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.

Therapeutic drug monitoring of levetiracetam in daily clinical practice: high-performance liquid chromatography versus immunoassay

Objectives

Although levetiracetam presents an easy dosing and tolerability, therapeutic drug monitoring may be recommended in certain situations. Measurement of levetiracetam in serum plasma is commonly done by high performance liquid chromatography (HPLC). After ARK Diagnostics marketed an enzyme immunoassay (IA) for levetiracetam in serum or plasma, automated determinations are possible. In this study, the performance of this immunoassay and the impact of automation on the follow-up in patients treated with levetiracetam is evaluated. We also detected those subpopulations of patients who may benefit the most from this therapeutic drug monitoring.

Methods

Samples from 50 outpatients diagnosed with epilepsy and treated with levetiracetam were collected. This new IA was performed on the Architect c4000 analyser and compared with the HPLC. Then, a retrospective observational study that included serum samples of levetiracetam for 24 months, was conducted to evaluate the impact of automattion and the influence of some variables (age, sex, renal function, and co-administration of valproic acid and glucuronidation-inducing drugs) in levetiracetam apparent oral clearance (CLp/F) by a multivariate linear regression.

Results

The mean high-performance liquid chromatography quantified concentration (CpHPLC) was 18.43 mcg/mL (95% CI: 15.48 to 21.39) and immunoassay concentration (CpEI) was 18.35 mcg/mL (95% CI: 15.20 to 21.50) (P=0.861). The Pearson's linear correlation coefficient obtained in the analysis was r²=0.88, according to the following equation: CpHPLC=-0.29+1.01 CpEI. The intraclass correlation coefficient was 0.95 (95% CI: 0.91 to 0.97). After IA implementation, the number of levetiracetam determinations increased in 76.27%. The median of Clp/F was higher (P<0.001) in inducers (4.36 L/h; IQR:3.29-5.44) and lower (P<0.001) in glomerular filtration rate (GFR) <60 mL/min (2.7 L/h; IQR: 0.58-3.85).

Conclusions

The Ark method performed on the Architect is fully acceptable and can be used routinely to measure levetiracetam plasmatic concentration levels. It has demonstrated the need for closer monitoring in patients with renal failure or co-administration of glucuronidation-inducing drugs.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Which information on women's issues in epilepsy does a community pharmacist need to know? A Delphi consensus study

OBJECTIVE

The aim of this study was to develop and achieve consensus on a core list of important knowledge items that community pharmacists should know on women's issues in epilepsy.

METHODS

This was a consensual study using a modified Delphi technique. Knowledge items were collected from the literature and from nine key contacts who were interviewed on their views on what information community pharmacists should have on women's issues in epilepsy. More knowledge items were suggested by five researchers with interest in women's issues who were contacted to rate and comment on the knowledge items collected. Two iterative Delphi rounds were conducted among a panel of pharmacists (n=30) to achieve consensus on the knowledge items to be included in the core list. Ten panelists ranked the knowledge items by their importance using the Analytical Hierarchy Process (AHP).

RESULTS

Consensus was achieved to include 68 knowledge under 13 categories in the final core list. Items ranked by their importance were related to the following: teratogenicity (10.3%), effect of pregnancy on epilepsy (7.4%), preconception counseling (10.3%), bone health (5.9%), catamenial epilepsy (7.4%), menopause and hormonal replacement therapy (2.9%), contraception (14.7%), menstrual disorders and infertility (8.8%), eclampsia (2.9%), breastfeeding (4.4%), folic acid and vitamin K (5.9%), counseling on general issues (14.7%), and sexuality (4.4%).

CONCLUSION

Using consensual knowledge lists might promote congruence in educating and/or training community pharmacists on women's issues in epilepsy. Future studies are needed to investigate if such lists can improve health services provided to women with epilepsy (WWE).

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.

A Systematic Appraisal of Neurosurgical Seizure Prophylaxis: Guidance for Critical Care Management

Clinical decisions are often made in the presence of some uncertainty. Health care should be based on a combination of scientific evidence, clinical experience, economics, patient value judgments, and preferences. Seizures are not uncommon following brain injury, surgical trauma, hemorrhage, altered brain metabolism, hypoxia, or ischemic events. The impact of seizures in the immediate aftermath of injury may be a prolonged intensive care stay or compounding of the primary injury. The aim of brain injury management is to limit the consequences of the secondary damage. The original intention of seizure prophylaxis was to limit the incidence of early-onset seizures. However, clinical trials have been equivocal on this point, and there is concern about the adverse effects of antiepileptic drug therapy. This review of the literature raises concerns regarding the arbitrary division of seizures into early onset (7 d) and late onset (8 d and beyond). In many cases it would appear that seizures present within 24 hours of the injury or after 7 days, which would be outside of the scope of current seizure prophylaxis guidance. There also does not appear to be a pathophysiological reason to divide brain injury-related seizures into these timeframes. Therefore, a solution to the conundrum is to reevaluate current practice. Prophylaxis could be offered to those receiving intensive care for the primary brain injury, where the impact of seizure would be detrimental to the management of the brain injury, or other clinical judgments where prophylaxis is prudent. Neurosurgical seizure management can then focus attention on which agent has the best adverse effect profile and the duration of therapy. The evidence seems to support levetiracetam as the most appropriate agent. Although previous reviews have identified an increase cost associated with the use of levetiracetam, current cost comparisons with phenytoin demonstrate a marginal price differential. The aim of this review is to assimilate the applicable literature regarding seizure prophylaxis. The final guidance is a forum upon which further clinical research could evaluate a new seizure prophylaxis paradigm.

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.

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.

Gender issues in antiepileptic drug treatment

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

The fetal safety of Levetiracetam: a systematic review

OBJECTIVE

To systematically review the available published evidence on the fetal safety of Levetiracetam with focus on birth defects.

RESULTS

Eight studies met the inclusion criteria; five pregnancy registries and one population based cohort study. A total of 27 major congenital malformations were reported among 1213 Levetiracetam monotherapy - exposed pregnant women, yielding an overall major malformation rate of 2.2% (27/1213) [95% confidence interval of 1.53-3.22]. In contrast, Levetiracetam polytherapy was associated with significantly higher malformation rate of 6.3% (34/541) [95% CI of 4.53-8.65] (P<0.001). Additionally 2 studies investigating child neurodevelopment in Levetiracetam - exposed children revealed that the measured achievements were well above those children exposed to valproic acid, and similar to unexposed controls.

CONCLUSIONS

The current evidence suggests that the overall risk of major malformation after first trimester exposure to Levetiracetam is within the population baseline risk of 1-3%, with no apparent adverse effects on long term child development.

Antiepileptic drug clearance and seizure frequency during pregnancy in women with epilepsy

The aims of the study were to characterize the magnitude of clearance changes during pregnancy for multiple antiepileptic drugs (AEDs) and to assess seizure frequency and factors increasing seizure risk in pregnant women with epilepsy. A retrospective analysis was performed for 115 pregnancies in 95 women with epilepsy followed at the Emory Epilepsy Center between 1999 and 2012. Antiepileptic drug blood levels (ABLs) obtained during routine clinical practice were used to calculate AED clearance at multiple points during pregnancy. Antiepileptic drug doses and seizure activity were also recorded. The data were analyzed for changes in clearance and dose across pregnancy and for an association between ABL and changes in seizure frequency. Significant changes in clearance during pregnancy were observed for lamotrigine (p<0.001) and levetiracetam (p<0.006). Average peak clearance increased by 191% for lamotrigine and 207% for levetiracetam from nonpregnant baseline. Marked variance was present across individual women and also across repeat pregnancies in individual women. Despite increased AED dose across most AEDs, seizures increased in 38.4% of patients during pregnancy. Seizure deterioration was significantly more likely in patients with seizures in the 12 months prior to conception (p<0.001) and those with localization-related epilepsy (p=0.005). When ABL fell >35% from preconception baseline, seizures worsened significantly during the second trimester when controlling for seizure occurrence in the year prior to conception. Substantial pharmacokinetic changes during pregnancy occur with multiple AEDs and may increase seizure risk. Monitoring of AED serum concentrations with dose adjustment is recommended in pregnant women with epilepsy. Further studies are needed for many AEDs.

Therapeutic drug monitoring in pregnancy

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

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

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

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.

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.