Pharmacokinetic changes and therapeutic drug monitoring of lamotrigine during pregnancy

Monitoring levetiracetam concentration in saliva during pregnancy is stable and feasible

AIMS

This multicenter prospective cohort study (registration no. ChiCTR2000032089) aimed to investigate the relationship between saliva and plasma levetiracetam concentrations to determine whether saliva could be used for routine monitoring of levetiracetam during pregnancy.

METHODS

The slot concentrations of levetiracetam in simultaneously obtained saliva and plasma samples were measured using UPLC-MS/MS. The correlations between saliva and plasma levetiracetam concentrations and the dose-normalized concentrations were compared among pregnant women in different stages and nonpregnant control participants with epilepsy.

RESULTS

In total, 231 patients with 407 plasma and saliva sample pairs were enrolled from 39 centers. Linear relationships between salivary and plasma levetiracetam concentrations were reported in the enrolled population (r = 0.898, p < 0.001), including pregnant (r = 0.935, p < 0.001) and nonpregnant participants (r = 0.882, p < 0.001). Plasma concentrations were moderately higher than saliva concentrations, with ratios of saliva to plasma concentrations of 0.98 for nonpregnant women, 0.98, 1, and 1.12 for pregnant women during the first trimester, the second trimester, the and third trimester, respectively. The effective range of saliva levetiracetam concentration was found to be 9.98 μg/mL (lower limit) with an area under the curve (AUC) of 0.937 (95% confidence intervals, 0.915-0.959), sensitivity of 88.9%, specificity of 86.8%, and p < 0.001, to 24.05 μg/mL (upper limit) with an AUC of 0.952 (0.914-0.99), sensitivity of 100%, specificity of 92.3%, and p = 0.007.

CONCLUSION

The saliva/plasma concentration ratio of levetiracetam remains constant during pregnancy and is similar to that in non-pregnant individuals. Monitoring levetiracetam concentration in saliva during pregnancy should be widely promoted.

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.

Anti-Seizure Monotherapy and Early Abortion Under Real-World Conditions

Background

Most pregnant epilepsy patients need to continue using anti-seizure medications (ASMs) to control epileptic seizures.

Objective

This study aimed to evaluate the risk of early abortion in pregnant epilepsy patients exposed to anti-seizure monotherapy.

Methods and Material

We prospectively followed up pregnant epilepsy patients treated with anti-seizure monotherapy in our epilepsy center between January 2010 and January 2020 under real-world conditions. Early abortion (spontaneous abortion in the first trimester of pregnancy) was the endpoint.

Results

Of 211 pregnancies exposed to monotherapy, including 40% (n = 85) to lamotrigine (LTG), 28% (n = 58) to oxcarbazepine (OXC), 15% (n = 32) to sodium valproate (VPA), 9% (n = 19) to levetiracetam, and 8% (n = 17) to carbamazepine, six ended in early abortion. The overall risk of early abortion in pregnant patients exposed to ASM monotherapy was 2.8% (n = 6) [95% confidence interval (CI) = 0.013-0.073]. The risk of early abortion was 2.4% (n = 2) (95% CI = 0.003-0.082) in women treated with LTG, 3.5% (n = 2) (95% CI = 0.004-0.115) in women treated with OXC, and 6.3% (n = 2) (95% CI = 0.008-0.208) in women treated with VPA. The relative risk of early abortion in the LTG, OXC, and VPA groups did not reach statistical significance.

Conclusions

Although the sample size of our study was small, these results indicate that the use of anti-seizure monotherapy in pregnant epilepsy patients may not increase the risk of early miscarriage. Larger prospective studies are needed for sufficient statistical analysis.

Optimizing Therapeutic Drug Monitoring in Pregnant Women: A Critical Literature Review

BACKGROUND

More than 90% of pregnant women take at least one drug during pregnancy. Drug dose adjustments during pregnancy are sometimes necessary due to various pregnancy-induced physiological alterations frequently associated with lower plasma concentrations. However, the clinical relevance or benefits of therapeutic drug monitoring (TDM) in pregnant women have not been specifically studied. Clinical pharmacokinetic studies in pregnant women are incredibly challenging for many reasons. Despite this, regulatory agencies have made efforts to encourage the inclusion of this population in clinical trials to achieve more information on the pharmacotherapy of pregnant women. This review aims to provide support for TDM recommendations and dose adjustments in pregnant women.

METHODS

The search was conducted after a predetermined strategy on PubMed and Scopus databases using the MeSH term "pregnancy" alongside other terms such as "Pregnancy and dose adjustment," "Pregnancy and therapeutic drug monitoring," "Pregnancy and PBPK," "Pregnancy and pharmacokinetics," and "Pregnancy and physiological changes."

RESULTS

The main information on TDM in pregnant women is available for antiepileptics, antipsychotics, antidepressants, antibiotics, antimalarials, and oncologic and immunosuppressive drugs.

CONCLUSIONS

More data are needed to support informed benefit-risk decision making for the administration of drugs to pregnant women. TDM and/or pharmacokinetic studies could ensure that pregnant women receive an adequate dosage of an active drug. Mechanistic modeling approaches potentially could increase our knowledge about the pharmacotherapy of this special population, and they could be used to better design dosage regimens.

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.

Dosage Optimization of Lamotrigine in Pregnancy: A Pharmacometric Approach using Modeling and Simulation

Lamotrigine is the most widely used anti-epileptic drug in pregnancy due to its low teratogenicity. However, there is an increased metabolism & clearance of Lamotrigine in pregnancy contributing to suboptimal drug therapy and poor disease control, prompting the need for pro-active dosage adjustments. The present study aimed to develop a pharmacometric model-based framework for recommending optimal dosage regimen for Lamotrigine in pregnancy. A systematic review was performed to obtain the literature aggregate data on clearance of Lamotrigine in pregnancy. The data was incorporated into simulations using PUMAS software for estimating the plasma concentrations at preconception stage and three trimesters. Simulated drug-exposures for different doses were investigated to ascertain plasma concentrations similar to the pre-conception and above minimum effective concentration. The simulated mean steady state trough plasma concentrations (mg/L) of Lamotrigine in non-pregnant and pregnant women at 3 trimesters decreased significantly (p<0.001) viz. 4.31±1.14, 3.17± 0.93, 2.14±0.86, 1.51±0.65 respectively. The simulation studies revealed that 150mg, 175mg, 225mg and 250mg twice daily doses, in pre-conception stage and three trimesters respectively achieve the target concentrations. Thus, the model-informed dosage regimen of Lamotrigine proposed in this study shall be considered to initiate the dosing in pregnant women, however the safety and efficacy of the drug have to be assured through therapeutic drug monitoring, in order to avoid therapeutic failure of Lamotrigine in pregnancy. This article is protected by copyright. All rights reserved.

Individualizing doses of antiepileptic drugs

INTRODUCTION

This review aims to identify the optimal therapeutic dosage of anti-epileptic drugs in terms of efficacy and safety in patients with multiple comorbidities.

AREAS COVERED

We have analyzed changes in terms of pharmacokinetics and pharmacodynamics of Brivaracetam, Carbamazepine, Lacosamide, Lamotrigine, Levetiracetam, Topiramate, Valproate, and Zonisamide in liver disease, chronic kidney disease, and in patients admitted to intensive care unit. Our literature search covers the past 5 years. We used PubMed, Google Scholar, and EMBASE database's to support our article.

EXPERT OPINION

To ensure that the patient with seizure receives the best treatment in relation to their comorbidities, careful clinical-laboratory monitoring is necessary to maximize effectiveness while maintaining safety, especially in the case of polytherapy.

Pharmacokinetic changes for newer antiepileptic drugs and seizure control during pregnancy

Objective

To investigate pharmacokinetic changes in newer antiepileptic drugs (AEDs) and assess seizure frequencies and risk factors of increased seizures during pregnancy in women with epilepsy (WWE).

Methods

A total of 56 pregnancies in 53 WWE who received newer antiepileptic drugs (AEDs) were enrolled. Data on seizure activity and types, daily dose, and AEDs blood levels were derived from routine clinical follow‐up. Changes in AEDs clearance were compared between each trimester and nonpregnant baseline. The ratio of AED levels of each trimester to their targets (nonpregnant baseline) concentrations (RTC) was compared between patients with and without an increased seizure. A binary logistic regression was used to investigate the risk factors contributing to seizure worsening during pregnancy.

Results

Increased clearances of LTG, LEV, and OXC were observed in all trimesters versus nonpregnant baseline. The peak changes in the clearance of LTG (3.42‐fold baseline clearance) (p < 0.001) and LEV (2.78‐fold) (p < 0.001) occurred in the second trimester during pregnancy, followed by oxcarbazepine (2.11‐fold) in the third trimester (p < 0.03). Plasma concentrations of LTG and LEV during pregnancy were significantly decreased compared to baseline levels, except for OXC. However, no significant differences in RTC values were observed between patients with and without seizure worsening. Some risk factors as seizures for the prior nine months could significantly affect seizure frequency during pregnancy.

Conclusion

We found substantial changes in the pharmacokinetics of multiple newer AEDs in WWE, reinforcing the need for therapeutic drug monitoring (TDM) during pregnancy. We would encourage at least one monitoring every trimester and probably more frequently for women with poorly seizure control before pregnancy, and AEDs dose adjustment should keep up with clearance changes. In addition, a well‐controlled seizure nine months before pregnancy could lower the risks of seizure during pregnancy, highlighting the importance of pre‐pregnancy counseling and seizure management before pregnancy.

Redefining the age-specific therapeutic ranges of lamotrigine for patients with epilepsy: A step towards optimizing treatment and increasing cost-effectiveness

OBJECTIVE

The pharmacokinetics of lamotrigine exhibits age-related characteristics. Nevertheless, current evidence regarding the therapeutic range of lamotrigine has been derived almost exclusively from studies in adult patients, and the applicability of this therapeutic range to the pediatric population remains unclear. The purpose of this study was to establish the appropriate age-specific therapeutic ranges of lamotrigine corresponding to adequate clinical responses for patients with epilepsy.

METHODS

This prospective cohort study of therapeutic drug monitoring included 582 Chinese epilepsy patients receiving lamotrigine monotherapy. Patients were divided into three age-related subgroups: (1) toddler and school-age group (2-12 years old, n = 168), (2) adolescent group (12-18 years old, n = 171), and (3) adult group (>18 years old, n = 243). Patients with a reduction in seizure frequency of 50 % or greater than baseline were defined as responders, and the remaining patients were non-responders. The relationship between lamotrigine serum concentrations and clinical response was assessed using multivariate logistic regression analysis. A receiver operating characteristic curve was generated to determine the representative cut-off values of lamotrigine trough levels, to distinguish responders from non-responders. The upper margin of the therapeutic range of lamotrigine was determined by developing concentration-effect curves for the three age-related subgroups.

RESULTS

The median trough levels of lamotrigine were significantly higher in responders than in non-responders from all three age-related groups (P < 0.0001). Results of logistic regression analysis revealed that higher serum concentrations of lamotrigine predicted a higher probability that seizure frequency would be reduced by more than 50 % compared to baseline (adjusted odds ratio: 1.228, 95 % CI: 1.137-1.327; P < 0.0001), and younger children were less likely to be responders (adjusted odds ratio: 1.027, 95 % CI: 1.012-1.043; P = 0.001). Based on a trade-off between sensitivity and specificity, the optimal cut-off values for lamotrigine trough concentrations corresponding to clinical response were 3.29 mg/L, 2.06 mg/L, and 1.61 mg/L in the toddler and school-age group, adolescent group, and adult group, respectively. By reducing interpatient variability, the results of the concentration-effect curves suggested no additional clinical benefit from a continued increase of doses for lamotrigine concentrations exceeding 9.08 mg/L, 8.43 mg/L, and 10.38 mg/L in the toddler and school-age group, adolescent group, and adult group, respectively. In conclusion, the therapeutic ranges of lamotrigine trough concentrations corresponding to adequate clinical response were 3.29-9.08 mg/L in the toddler and school-age group, 2.06-8.43 mg/L in the adolescent group, and 1.61-10.38 mg/L in the adult group.

CONCLUSIONS

The study determined age-specific therapeutic ranges corresponding to optimal clinical efficacy for lamotrigine. Our findings lay the foundation for catalyzing novel opportunities to optimize treatment and reduce therapeutic costs. Based on the age-specific therapeutic ranges identified in this study, individualized and cost-effective algorithms for lamotrigine treatment of epilepsy patients may be developed and validated in larger cohort studies of therapeutic drug monitoring.

Estrogen profile- and pharmacogenetics-based lamotrigine dosing regimen optimization: Recommendations for pregnant women with epilepsy

During pregnancy, various physiological changes occur that can alter the pharmacokinetics of antiepileptic drugs, such as lamotrigine (LTG). Anticipating the change in LTG dose required to achieve a pre-pregnancy target concentration is challenging. This study aimed to develop a refined population pharmacokinetic (PopPK) model of LTG in pregnant women with epilepsy (WWE) to identify factors explaining the variability in pharmacokinetics and to establish a model-informed individualized dosing regimen. On that basis, a coarsened model containing only clinical variables was also developed to examine its predictive performance compared to the refined model. In total, 322 concentration-time points from 51 pregnant WWE treated with LTG were employed to establish a refined PopPK model that included endogenous estrogen profiles, variants of candidate genes encoding LTG-metabolizing enzymes and -transporter proteins, and other clinical variables and a coarsened model that included only clinical variables, respectively. Data from an additional 11 patients were used for external validation of these two models. A nonlinear mixed-effect modeling approach was used for PopPK analysis of LTG. The standard goodness-of-fit method, bootstrap, normalized prediction distribution errors and external evaluation were adopted to estimate the stability and predictive performance of the candidate models. Akaike information criterion (AIC) was used to compare the goodness of fit between these two models. A lower AIC indicates a better fit of the data and the preferred model. Recommended dosing regimens for pregnant WWE were selected using Monte Carlo simulation based on the established optimal model. In the refined PopPK model, the population mean of apparent LTG clearance (CL/F) in pregnant WWE was estimated to be 2.82 L/h, with an inter-individual variability of 23.6%. PopPK analysis indicated that changes in estrogen profile during pregnancy were the predominant reason for the significant variations in LTG-CL/F. Up to the 3rd trimester, the concentration accumulation effect of E2 increased LTG-CL/F by 5.109 L/h from baseline levels. Contrary to effect of E2, E3 as the main circulating estrogen in pregnancy with a peak value of 34.41 ng/mL is 1000-fold higher than that in non-pregnancy reduced LTG-CL/F by 1.413 L/h. In addition, the UGT2B7 rs4356975 C > T and ABCB1 rs1128503 A > G variants may contribute to a better understanding of the inter-individual variability in LTG-CL/F. LTG-CL/F was 1.66-fold higher in UGT2B7 rs4356975 CT or TT genotype carriers than in CC genotype carriers. In contrast, ABCB1 rs1128503 GG genotype carriers had only 71.9% of the LTG-CL/F of AA or AG genotype carriers. In the coarsened PopPK model, the gestational age was a promising predictor of changes in LTG-CL/F. When comparing these two models, the refined PopPK model was favored over the coarsened PopPK model (AIC = -30.899 vs. -20.017). Monte Carlo simulation based on optimal PopPK model revealed that the LTG dosage administered to carriers of the UGT2B7 rs4356975 CT or TT genotype required a 33-50% increase to reach the pre-pregnancy target concentration, and carriers of the ABCB1 rs1128503 GG genotype required a 33-66% lower dose of LTG than carriers of the ABCB1 rs1128503 AA or AG genotype. Changes in estrogen profile during pregnancy was a better predictor of variations in LTG-CL/F than gestational age. The developed model based on estrogen profile and pharmacogenetics can serve as a foundation for further optimization of dosing regimens of LTG in pregnant WWE.

Therapeutic monitoring of antiepileptic drugs: Recommendations to improve care of patients with epilepsy in the Palestinian practice

BACKGROUND

Therapeutic drug monitoring (TDM) can play a major role in optimizing pharmacotherapy of epilepsy. This study was conducted to explore views and opinions of clinicians who care for patients with epilepsy (PWE) in Palestine and to develop consensus-based recommendations with regard to importance, justification, technical, and analytical issues of TDM of antiepileptic drugs (AEDs).

METHODS

The study was conducted in three phases: (1) the published literature was thoroughly searched for an initial list of items relevant to TDM of AEDs, (2) the list was supplemented by items provided by key experts (n = 8) through semi-structured in-depth interviews, (3) views and opinions of clinicians (n = 20) on TDM of AEDs were explored, and (4) a two-round Delphi technique was followed among a panel of experts (n = 27) to develop consensus-based recommendations to guide TDM of AEDs in Palestine.

RESULTS

Consensus was achieved on items related to importance (8 items) of TDM of AEDs, clinical justifications of TDM of AEDs (19 items), guidelines for optimal TDM of AEDs (11 items), TDM of some AEDs (21 items), TDM practice (24 items), and some technical and analytical issues in TDM of AEDs (13 items).

CONCLUSION

Consensus-based recommendations that might be used in guiding TDM of AEDs in Palestine were developed. Future studies are still needed to investigate if these consensus-based recommendations can improve healthcare of PWE in Palestine.

Understanding and Responding to Prescribing Patterns of Sodium Valproate-Containing Medicines in Pregnant Women and Women of Childbearing Age in Western Cape, South Africa

INTRODUCTION

Growing evidence of the teratogenic potential of sodium valproate (VPA) has changed prescribing practices across the globe; however, the impact of this research and the consequent dissemination of a Dear Health Care Professional Letter (DHCPL) in December 2015, recommending avoidance of the teratogen VPA in women of childbearing age (WOCBA) and pregnant women in South Africa, is unknown. We explored trends and reasons for VPA use among pregnant women and WOCBA in the public sector in Western Cape Province from 1 January 2015 to 31 December 2017.

METHODS

Using the provincial health information exchange that collates routine electronic health data via unique patient identifiers, we analysed clinical and pharmacy records from 2015 to 2017 to determine prescription patterns of VPA and other antiepileptic drug (AED) and mood-stabilising medicine (MSM) use in WOCBA and pregnant women. Senior clinicians and policy makers were consulted to understand the determinants of VPA use.

RESULTS

At least one VPA prescription was dispensed to between 8205 (0.79%) and 9425 (0.94%) WOBCA from a cohort of approximately 1 million WOCBA attending provincial health care facilities per year. Prescriptions were more likely in HIV-infected women compared with HIV-uninfected women (1.1-1.3% vs. 0.7-0.9%; p < 0.001). VPA use in WOCBA remained stable at 0.8-0.9% over the review period despite the 2016 DHCPL. VPA was the most prescribed AED/MSM, constituting 43.2-45.5% of all WOCBA taking at least one such agent, while lamotrigine, the other recommended first-line agent, was only prescribed in 7.8-8.9% of WOCBA. Over 3 years, approximately 663 pregnancies were exposed to VPA, with a steady rise in the number of exposures each year (n = 204, 214 and 245, respectively).

CONCLUSION

Despite warnings, VPA remained the most frequently prescribed AED or MSM in WOCBA. Contributing factors are described.

Affective disorders: A question of continuing treatment during pregnancy (Review)

Fetal development, especially in the first trimester, has proven to be heavily influenced by external factors, such as chemical intake of medication. Chronic psychiatric treatment might interfere with the anatomical and physiological wellbeing of the fetus, because psychotropic medication proceeds past the placenta, into the amniotic fluid, and can enter breast milk. Hence some of the medications prescribed for mood disorders should be reconsidered during pregnancy, without sub-optimally treating when it is needed. A literature review is presented which systematically collects modern data and synthesizes previous interdisciplinary research findings on the safety of psychiatric treatment for affective disorders during pregnancy (term-based) and lactation. Antidepressants and mood stabilizers, fundamental strategies in treating affective disorders, have been classified by the FDA as C respectively D drugs pertaining to their risk, with some exception. Most guidelines recommend pharmacologically treating moderate-severe depression, preferably with SSRIs. Evidence advocates that drugs should be used during pregnancy only if clearly needed and the benefit outweighs the risk to the fetus. However, guidelines the American College of Obstetricians and Gynecologists state that antidepressants are a preferred first course of treatment and does not take into account the severity of the depression. Among mood-stabilizers, lithium is considered to be the safest option for pregnant women. Anticonvulsants have a higher risk of teratogenicity compared with lithium, with lamotrigine being the safest one. All mood stabilizers should be recommended in the lowest effective doses. There is controversy regarding the safety of second-generation antipsychotics during pregnancy and further research is required. Several case reports and meta-reviews have been published in order to emphasize the safety of electroconvulsive therapy (ECT) during pregnancy, but practitioners still stigmatize this procedure. Evaluating the overall risk-benefit ratio should be assessed by the medical care provider, taking into consideration current findings.

Pharmacokinetic changes and therapeutic drug monitoring of lamotrigine during pregnancy

OBJECTIVES

To evaluate the pharmacokinetic changes in lamotrigine (LTG) from prepregnancy to postpartum and to assess the impact of therapeutic drug monitoring (TDM) on seizure management during pregnancy in a Chinese population.

METHODS

A series of women who were on LTG monotherapy before conception or during pregnancy were included in this retrospective study. The clinical characteristics of the mothers and fetuses were collected. The apparent clearance (AC) and the ratio to target concentration (RTC) were calculated for each trimester or for each month. RTCs were compared between patients with and without an increase in the frequency of seizures. A receiver operating characteristic curve to determine the RTC threshold, which predicts increased seizure frequency best, was drawn.

RESULTS

A total of 12 patients and their 12 pregnancies were reviewed retrospectively. AC increased by 82.5% during the first trimester (p = 0.0343), 203.2% during the second trimester (p = 0.0010), and 197.0% during the third trimester (p = 0.0061) compared with the prepregnancy level. The value returned to the prepregnancy level after delivery. Seven patients who had adequate baseline information were included to examine the association between serum LTG concentration and seizure frequency. The RTC values of patients with and without an increased frequency of seizures were significantly different (p = 0.0164), and increased seizure frequency was associated with a lower RTC. An RTC < 0.64 was a predictor of deteriorating seizures.

CONCLUSIONS

The pharmacokinetic changes in LTG during pregnancy displayed marked interpatient variation. TDM can support a rational treatment plan for LTG use during pregnancy. We recommend regular monitoring of LTG serum concentrations from prepregnancy to postpartum.