Association of Levetiracetam Concentration With Seizure Frequency in Pregnant Women With Epilepsy

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.

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.

Dose Monitoring of Lamotrigine Monotherapy in Pregnancy: Are Pregnant Women with Epilepsy Currently Optimally Managed? A Systematic Review

BACKGROUND

Lamotrigine monotherapy is the first-line treatment for epilepsy in pregnant women. However, altered pharmacokinetics during pregnancy can lead to suboptimal drug levels and increased seizure risk. This systematic review aimed to evaluate current therapeutic drug monitoring (TDM) strategies for lamotrigine monotherapy in pregnant women with epilepsy and provide guidance for monitoring and dose adjustments.

METHODS

A systematic search was performed using the Ovid-MEDLINE, Ovid-EMBASE, and Ovid-Cochrane Central Register of Controlled Trials databases. Studies were included if data on lamotrigine dosing, concentration, TDM strategies, efficacy, or safety were available.

RESULTS

Eleven studies were analyzed, revealing heterogeneity in outcomes with selective reporting of TDM strategies; however, clear similarities were observed. Blood samples were collected every 1-3 months during pregnancy to maintain prepregnancy baseline drug levels. Lamotrigine's apparent and relative clearance increased across trimesters, particularly in the second and third trimesters, coinciding with a period of increased seizure frequency and required dose adjustments. Details on dose adjustments were limited. Some studies have proposed using the threshold of the ratio to the target concentration to predict increased seizure risk. No distinct association was observed between adverse newborn outcomes and lamotrigine dose or serum concentration. Few maternal adverse effects have been reported after delivery, confirming the necessity of empirical postpartum tapering.

CONCLUSIONS

Further studies are required to establish evidence-based standardized protocols encompassing all aspects of TDM. Early interventions, such as empirical dose increases during pregnancy and postpartum tapering, and routine monitoring from preconception to the postpartum period may enhance seizure control, reducing the risk of breakthrough seizures for the mother and unborn child.

Quantitation of levetiracetam concentrations in plasma and saliva samples by ultra-performance liquid chromatography-tandem mass spectrometry: Application to therapeutic drug monitoring for pregnant women with epilepsy

Although levetiracetam (LEV) has favorable linear pharmacokinetic properties, therapeutic drug monitoring (TDM) is necessary for pregnant women with epilepsy. This study aims to build a simple, reliable, and sensitive ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for determining LEV concentrations in plasma and saliva samples, to support the routine TDM of LEV in Chinese pregnant women with epilepsy. The stable isotope-labeled LEV-d6 was used as the internal standard. The extracted samples were analyzed using a UPLC-MS/MS system with positive electrospray ionization. Mobile phase A was water containing 5 mM ammonium acetate and 0.1% formic acid, and phase B was 1:1 methanol-acetonitrile with 0.1% formic acid. The method was validated and utilized to determine LEV concentrations in non-pregnant and pregnant patients with epilepsy. The developed method was validated in both plasma and saliva samples over a concentration range of 0.1-50 μg/mL. The intra- and inter-batch accuracy for LEV ranged from -7.0% to 2.9%, with precisions between 2.7% and 9.3%. In pregnant patients, the mean dose-standardized LEV trough plasma concentrations were significantly lower than those in non-pregnant patients (4.73 ± 2.99 vs. 7.74 ± 3.59 ng/mL per mg/day; P < 0.0001). It is recommended that the TDM of LEV should be routinely performed during the different stages of pregnancy.

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

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

Issues of Women with Epilepsy and Suitable Antiseizure Drugs

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

Management of epilepsy during pregnancy and lactation

Epilepsy is a group of neurological diseases characterized by susceptibility to recurrent seizures. Antiseizure medications (ASMs) are the mainstay of treatment, but many antiseizure medications with variable safety profiles have been approved for use. For women with epilepsy in their childbearing years, the safety profile is important for them and their unborn children, because treatment is often required to protect them from seizures during pregnancy and lactation. Since no large randomized controlled trials have investigated safety in this subgroup of people with epilepsy, pregnancy registries, cohort and case-control studies from population registries, and a few large prospective cohort studies have played an important role. Valproate, in monotherapy and polytherapy, has been associated with elevated risk of major congenital malformations and neurodevelopmental disorders in children born to mothers who took it. Topiramate and phenobarbital are also associated with elevated risks of congenital malformations and neurodevelopmental disorders, though the risks are lower than those of valproate. Lamotrigine and levetiracetam are relatively safe. Insufficient data exist to reach strong conclusions about the newest antiseizure medications such as eslicarbazepine, perampanel, brivaracetam, cannabidiol, and cenobamate. Besides antiseizure medications, other treatments such as vagal nerve stimulation, responsive neurostimulation, and deep brain stimulation are likely safe. In general, breastfeeding does not appear to add any additional long term risks to the child. Creative ways of optimizing registry enrollment and data collection are needed to enhance patient safety.