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Background: Lamotrigine is a new antiepileptic drug with substantial interindividual variability in its pharmacokinetics and therapeutic responses. This study aimed to develop population pharmacokinetic (PPK) models of lamotrigine and its N2-glucuronide metabolites for model-informed individualized therapy., Methods: A total of 353 plasma concentrations from Chinese patients with epilepsy receiving oral lamotrigine were used to develop a population PPK model using a nonlinear mixed effects modeling method. One- and two-compartment models were applied to the nonmetabolite and metabolite model, respectively. Forward addition and backward elimination were used to establish the final model. Model validation was performed using standard goodness-of-fit, bootstrap, visual predictive checks, and normalized prediction distribution errors. Finally, simulations were performed to propose lamotrigine dosages in different situations to achieve trough concentrations within the reference interval (2.5-15 mg/L)., Results: For both final population PPK models, coadministration with valproic acid (VPA) or enzyme inducer, and body weight significantly affected lamotrigine clearance. The final models for lamotrigine clearance were and for nonmetabolite and metabolite models, respectively. The precision of the PPK parameters was acceptable, and the models exhibited good predictability. Monte Carlo simulations revealed that the lamotrigine dosage administered to patients combined with an enzyme inducer must be tripled that administered with VPA to reach the target trough concentration., Conclusions: Variability in the pharmacokinetics of lamotrigine is large. Coadministration of VPA or an enzyme inducer and body weight are the most important factors in lamotrigine clearance in Chinese patients with epilepsy. The developed population PPK models might support further optimization of lamotrigine dosing regimens., Competing Interests: The authors declare no conflict of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

The mTOR signaling pathway has emerged as a possible therapeutic target for epilepsy. Clinical trials have shown that mTOR inhibitors such as everolimus reduce seizures in tuberous sclerosis complex patients with intractable epilepsy. Furthermore, accumulating preclinical data suggest that mTOR inhibitors may have anti-seizure or anti-epileptogenic actions in other types of epilepsy. However, the chronic use of rapalogs such as everolimus is limited by poor tolerability, particularly by immunosuppression, poor brain penetration and induction of feedback loops which might contribute to their limited therapeutic efficacy. Here we describe two novel, brain-permeable and well tolerated small molecule 1,3,5-triazine derivatives, the catalytic mTORC1/C2 inhibitor PQR620 and the dual pan-PI3K/mTOR inhibitor PQR530. These derivatives were compared with the mTORC1 inhibitors rapamycin and everolimus as well as the anti-seizure drugs phenobarbital and levetiracetam. The anti-seizure potential of these compounds was determined by evaluating the electroconvulsive seizure threshold in normal and epileptic mice. Rapamycin and everolimus only poorly penetrated into the brain (brain:plasma ratio 0.0057 for rapamycin and 0.016 for everolimus). In contrast, the novel compounds rapidly entered the brain, reaching brain:plasma ratios of ∼1.6. Furthermore, they significantly decreased phosphorylation of S6 ribosomal protein in the hippocampus of normal and epileptic mice, demonstrating effective mTOR inhibition. PQR620 and PQR530 significantly increased seizure threshold at tolerable doses. The effect of PQR620 was more marked in epileptic vs. nonepileptic mice, matching the efficacy of levetiracetam. Overall, the novel compounds described here have the potential to overcome the disadvantages of rapalogs for treatment of epilepsy and mTORopathies directly connected to mutations in the mTOR signaling cascade., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Purpose: The aims of this study were to develop a population pharmacokinetic (PPK) model of lamotrigine (LTG) in Chinese epileptic children by using nonlinear mixed effects modeling (NONMEM) and to investigate the effects of valproic acid (VPA) and genetic polymorphisms of the major metabolizing enzymes (UGT1A4, UGT2B7) on the pharmacokinetics of LTG., Methods: A total of 182 epileptic children who were treated with LTG as monotherapy or as part of combination therapy were included in this study as the model group, and 61 patients were included as the validation group. The steady-state serum trough concentrations of LTG and VPA were determined using a high-performance liquid chromatography method and fluorescence polarization immunoassay, respectively. Patients were genotyped for three single nucleotide polymorphisms (UGT1A4 142T>G, UGT2B7 -161C>T, and UGT2B7 802C>T). PPK analysis was performed with NONMEM using first-order absorption and elimination. Bootstrap, normalized prediction distribution errors and external evaluations were performed to determine the stability and predictive performance of the model., Results: For the final model, the oral clearance (CL/F) of LTG was estimated to be 0.705 L/h with inter-individual variability (IIV) of 21.3%. The estimates generated by NONMEM indicated that the LTG CL/F was significantly influenced by patient body weight (increased with an exponent of 0.574) and VPA concentration (decreased with linearity of 0.273 with co-administration). However, no significant effects of UGT1A4 or UGT2B7 polymorphisms on LTG CL/F were noted in this population of Chinese children., Conclusion: This study confirms the interaction of LTG with VPA, which likely depends on VPA concentration. The LTG PPK model developed in this study could be useful for individualizing LTG dosage regimens in pediatric patients receiving combination therapy, especially therapy that includes VPA.

Purpose: Conversion to lamotrigine (LTG) monotherapy from sodium valproate (VPA) is complicated by the robust pharmacokinetic interaction between the two AEDs. This study examined changes in LTG serum concentrations immediately following VPA discontinuation., Methods: Ten healthy female and male adult subjects were initiated on LTG (Lamictal) 10 mg orally every morning for 30 days and VPA (Depakote ER) 500 mg orally every morning for 14 days. Morning trough (pre-dose) venous blood samples were obtained for determination of LTG and VPA concentrations on study days 14, 15, 16, 18, 20, 22, 24, 26, 28, and 30. Following the collection of the blood sample on day 15, VPA was discontinued., Results: Despite stable LTG dosage serum concentrations on study day 20, 22, 24, 26, and 28, all were significantly lower compared to baseline (p < 0.05)., Conclusions: These observations demonstrate that the pharmacokinetic interaction between LTG and VPA is reversible, and that de-inhibition appears to follow a predictable time course. Complete offset, or reversal of this interaction takes place 10-14 days after VPA discontinuation. Our data also confirms the observation that LTG oral clearance may be inhibited by very low concentrations of VPA. These data support the conversion algorithm suggested by the manufacturer, and provide guidance to the clinician. These data provide clinically useful information in developing a dosing algorithm for converting patients to LTG monotherapy., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Valproic acid(VPA) is a classic drug that used to treat epilepsy in monotherapy or combination with other anticonvulsant drugs such as lamotrigine (LTG). Although it was reported that VPA could increase lamotrigine trough concentration in clinical practice, there was no report about the effect of LTG on the trough concentration of VPA and its main metabolites, such as 4-ene-VPA, 3-OH-VPA, 4-OH-VPA, 3-keto-VPA, 2-PGA which are related to the therapeutic and toxic effects of VPA. In this study, a simple and rapid method for the simultaneous determination of VPA and its five metabolites in human plasma using HPLC-MS/MS was developed for the first time. Benzoic acid was used as an internal standard (IS). Separation was performed on a Hypersil GOLD C 18 column by isocratic elution using acetonitrile: 10mM ammonium acetate solution (90:10, v/v) as mobile phase at a flow rate of 0.3mL/min. A triple quadrupole mass spectrometer operating in the negative ion-switching, electron spray ionization mode with selection reaction monitoring (SRM) was employed to determine transitions of m/z 143.183→143.183, 157.033→113.165, 173.017→129.074, 159.058→101.082, 140.870→140. 870, 159.049→123.076, 121.035→77.136 for VPA, 2-PGA, 3-keto-VPA, 3-OH-VPA, 4-ene-VPA, 4-OH-VPA and IS, respectively. The method also afforded satisfactory results in terms of sensitivity, specificity, precision (intra- and inter-batch), accuracy, recovery, matrix effect and stability. This method was successfully applied to evaluate the effect of LTG on the trough concentration of VPA, 2-PGA, 3-keto-VPA, 3-OH-VPA, 4-ene-VPA, 4-OH-VPA in Chinese epilepsy patients. The result showed that there was no significant difference in the concentration of VPA and its five metabolites between patients in VPA monotherapy and patients in therapy combining VPA with LTG., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: Antiepileptic drug titration in epilepsy remains mostly empirical. Since in practice seizure remission may be obtained with low doses, we aimed to determine whether patients in remission have lower lamotrigine levels than those with ongoing seizures., Methods: Retrospective comparison of the distribution of lamotrigine levels among unselected patients in remission and with ongoing seizures. Remission was defined as 3 times the longuest interseizure interval and at least one year. Only trough levels were analyzed., Results: Between 2009 and 2014, we identified 93 adults, among whom 10 were in remission. Patients in remission had significantly (p=0.008) lower serum levels (median 2.3mg/L, range: 0.7-8.2) than those with ongoing seizures (median 5.4mg/L, range: 1.1-18.2). We did not find any patient in remission with levels higher than 8.2mg/L. Distribution of dosages also differed among the groups, but less significantly (median: 175 vs 300mg, p=0.03)., Conclusion: An association between lamotrigine serum levels and seizure response can be observed. This suggests the existence of a ceiling level, above which remission is unlikely and should prompt antiepileptic medication switch rather than further up-titration of lamotrigine in drug-naïve patients with epilepsy., (Copyright © 2017 Elsevier Inc. All rights reserved.)

This study was conducted to evaluate the effectiveness of lamotrigine (LTG) over 2 years and the usefulness of measuring its blood levels during the follow-up of patients with epilepsy. We measured peak blood LTG levels of 32 patients with epilepsy (9.16 ± 3.34 years old; mean ± SD). The blood levels were measured at 6 months, 1 year, and 2 years after reaching the LTG maintenance dosage. The effectiveness of LTG was evaluated to determine the seizure reduction rate. The patients were classified as effective cases (mean of own seizure reduction rates >50%) and ineffective cases (≤50%). The results were that the dosage and blood level showed positive correlations in the case of combination use with sodium valproate (VPA) (r = 0.690), carbamazepine and/or phenobarbital (r = 0.940), and others (r = 0.548). In several groups, the blood levels and efficacies did not show any positive correlations. In the cases of combination use with VPA, the blood levels of effective cases and ineffective cases were significantly different (P = 0.001). The optimal range was 8-11.5 μg/mL based on the average and SD values in the effective cases. No patients had any side effects. In conclusion, no precise definition of the therapeutic range was possible because of the incomplete correlation between the blood level and seizure frequency. We recommend the optimal range of LTG as a therapeutic target without any side effects, and it was established that the range in the combination with VPA was 8-11.5 μg/mL.

Importance: Switching between generic antiepileptic drugs is a highly debated issue that affects both clinical care and overall health care costs., Objective: To evaluate the single-dose pharmacokinetic bioequivalence of 3 (1 branded and 2 generic drugs) on-market, immediate-release lamotrigine drug products., Design, Setting, and Participants: The Equivalence Among Antiepileptic Drug Generic and Brand Products in People With Epilepsy (EQUIGEN) single-dose study is a crossover, prospective, sequence-randomized, replicate pharmacokinetic study conducted at 5 US academic epilepsy centers. Fifty adults (≥18 years) with epilepsy who were taking concomitant antiepileptic drugs and not currently receiving lamotrigine were enrolled between July 18, 2013, and January 19, 2015. Every participant was randomly assigned to 1 of 3 equivalent sequences, each comprising 6 study periods, during which they had blood draws before and after medication administration. Forty-nine participants were included in intention-to-treat analyses., Interventions: Participants received a single 25-mg dose of immediate-release lamotrigine at the start of each period, with the branded and the 2 most disparate generic products each studied twice. Lamotrigine was selected as the antiepileptic drug of interest because of its wide use, publications indicating problems with generic switches, and complaints to the US Food and Drug Administration regarding generic products. Both participants and study personnel were blinded to the specific generic products selected., Main Outcomes and Measures: The primary outcome was bioequivalence between products. Maximum plasma concentration (Cmax) and area under the concentration-time curve (AUC) were compared, and average bioequivalence (ABE) was established if the 90% CIs of the ratios of the 2 products were within equivalence limits (80%-125%)., Results: Of the 50 randomized participants, 49 (98%) received all 3 lamotrigine products and completed at least 3 pharmacokinetic assessments and 46 (92%) completed all 6 pharmacokinetic assessments. Among the 49 participants, 28 (57%) were men and 21 (43%) were women, 42 (86%) self-identified as white, and 46 (16) years was the mean (SD) age. The 3 drug products were considered bioequivalent because the 90% CIs were within equivalence limits (lowest and highest CI limits for Cmax, 92.6% and 110.4%; for AUC0-96, 96.9% and 101.9%). Replicate testing demonstrated no significant differences in within-subject variability across the 3 products (likelihood ratios, χ22 for log-transformed variables: AUC0-96, 2.58; Cmax, 0.64; and AUC0-∞, 4.05; P ≥ .13) and that the 3 products were also bioequivalent according to scaled ABE and individual bioequivalence criteria with no subject × formulation interaction (Cmax, 0.00; AUC0-96, 0.54; and AUC0-∞, 0.36; P ≥ .76)., Conclusions and Relevance: This study provides evidence that the disparate lamotrigine products studied are bioequivalent when tested in people with epilepsy taking concomitant antiepileptic drugs., Trial Registration: clinicaltrials.gov Identifier: NCT01733394.

Objectives: The objective of this study was to evaluate possible nonlinear lamotrigine (LTG) pharmacokinetics at elevated concentration. LTG is reported to have linear kinetics, so that elimination rate is linearly proportional to blood concentration and a change in dose is accompanied by a proportionate change in serum concentration. We encountered patients in whom LTG serum concentration increased dramatically in response to minor or no change in LTG dose. We studied this phenomenon in patients with LTG toxicity in one clinic., Materials and Methods: Using electronic medical records from 1997 to 2014, we identified patients who developed clinical LTG toxicity with LTG serum concentrations >20 mg/l, after tolerating lamotrigine at lower serum concentrations. We reviewed LTG dose change and other changes that preceded the episode of toxicity., Results: Twenty-two patients had at least one episode of LTG toxicity with levels higher than 20 mg/l (of 922 patients with available levels). The peak serum concentration varied from 21.1 to 40.3 mg/l (mean 28.7). The increase in level was explained in three patients (post-delivery in one, addition of valproate in two). In the 18 others, the increase was not explained or it was disproportionate to an increase in LTG dose., Conclusions: Spikes in LTG levels and associated clinical toxicity may occur unexpectedly, suggesting that elimination kinetics may be nonlinear in some individuals at serum concentrations in the upper range. Measurement and close monitoring of LTG levels is warranted for new symptoms that could be consistent with lamotrigine toxicity, particularly when the baseline serum concentration has been >10 mg/l., (© 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Lamotrigine (LTG) is an antiepileptic drug that is metabolized via glucuronidation. Since the glucuronidizing enzyme is inducible by estrogens, LTG serum concentrations may fall by 50-60% when combined with hormonal contraceptives that contain ethinyl estradiol (EE). Little is known about a possible interaction between estrogens used for hormone replacement therapy (HRT) and LTG, and the few available data are conflicting. Data from serum samples analyzed for LTG were therefore retrieved from a routine therapeutic drug monitoring database. Users of HRT and EE were identified and matched with controls for age and dose. No enzyme-inducing or enzyme-inhibiting comedication was allowed. LTG serum concentration-to-dose ratios (CDRs) were calculated. Case groups and their respective control groups were compared by the Mann-Whitney U test. Seventy-nine HRT users (dose range 1-4 mg/day) and 200 EE users (dose range 20-40 μg/day), as well as 158 and 400 matching controls, respectively, could be included. Both EE users and HRT users had significantly lower mean LTG CDRs than their respective matched controls. These results suggest that HRT with estrogens may reduce serum LTG concentrations., (Wiley Periodicals, Inc. © 2016 International League Against Epilepsy.)

Purpose: The pharmacokinetics of Lamotrigine (LTG) varies widely among patients with epilepsy. In this study, we are aiming to investigate the effects of OCT1, ABCG2, ABCC2 and HNF4α genetic polymorphisms on plasma LTG concentrations and therapeutic efficacy in Chinese patients with epilepsy., Methods: The study cohort comprised 112 Han Chinese patients with epilepsy who were receiving LTG monotherapy. Blood samples were taken and LTG levels were measured. The polymorphisms of OCT1 rs2282143, rs628031, ABCG2 rs2231142, rs2231137, ABCC2 rs2273697 and HNF4α rs2071197, rs3212183 were determined. The therapeutic efficacy of LTG at the 1-year time-point was assessed. Data analysis was performed using IBM SPSS Statistics 22.0., Results: There were significant associations between OCT1 rs628031, ABCG2 rs2231142 polymorphisms and normalized LTG concentrations in patients with epilepsy (P<0.05). On the other hand, polymorphisms of OCT1 rs2282143, ABCG2 rs2231137, ABCC2 rs2273697 and HNF4α rs2071197, rs3212183 exhibited no correlation with LTG concentrations. Additionally, no significant association existed between all the studied genotypes and LTG treatment response., Conclusions: These results suggested that the polymorphisms of OCT1 rs628031 and ABCG2 rs2231142 may affect LTG metabolism in Chinese patients with epilepsy. However, future studies are necessary to be investigated in a larger cohort of epileptic patients., (Copyright © 2016. Published by Elsevier B.V.)

A simple and rapid high-performance liquid chromatography method with diode-array detection (HPLC-DAD) using microextraction by packed sorbent (MEPS) during the sample preparation step was developed and validated to quantify lamotrigine (LTG) in rat plasma and brain samples. MEPS variables such as pH, number of draw-eject cycles, and washing and desorption conditions were optimized. The chromatographic resolution of LTG and chloramphenicol, used as internal standard (IS), was accomplished in less than 5min on a C18 column, at 35°C, using an isocratic elution with acetonitrile (13%), methanol (13%) and water-triethylamine (99.7:0.3, v/v; pH 6.0) pumped at a flow rate of 1mL/min. Detection was performed at 215nm. Calibration curves were linear over the range of 0.1-20μg/mL (r 2 ≥0.9947) for LTG in both rat plasma and brain homogenate samples. The intra and interday imprecision did not exceed 8.6% and the intra and interday inaccuracy ranged from -8.1 to 13.5%. LTG was extracted from rat plasma and brain homogenate samples with an average absolute recovery ranging from 68.0 to 86.7%, and its stability was demonstrated in the assayed conditions. No interferences were observed at the retention times of the analyte (LTG) and IS. To the best of our knowledge, this is the first bioanalytical assay that uses MEPS procedure for the determination of LTG not only in rat plasma but also in tissue (brain) samples. This novel method was successfully applied to a preliminary pharmacokinetic study in rats and it seems to be a cost-effective tool to support non-clinical pharmacokinetic-based studies involving LTG treatment., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Aim: Recently, polytherapy regimen has been introduced for the treatment of epileptic patients for better seizure control with lesser side effects and better control of multiple seizure types., Methodology: A simple, sensitive and highly specific reversed-phase HPLC method was developed for simultaneous determination of four antiepileptic drugs (AEDs), levetiracetam, lamotrigine, oxcarbazepine and carbamazepine, in real human plasma without interference from endogenous components of plasma., Conclusion: The method was proved to be linear in the range of 0.5-50 µg/ml for all drugs. It was successfully applied for clinical PK study of the AEDs in healthy volunteers following single administration. Also, this method was applied for simultaneous determination of the studied drugs in volunteers' plasma receiving synergistic binary combinations from the four AEDs when used as add-on therapy. The good precision and selectivity of the developed method allow it to be used for routine therapeutic drug monitoring of such drugs as a useful tool in epilepsy management.

BACKGROUND This study aimed to analyze the relationship of UGT2B7 and UGT1A4 polymorphisms with metabolism of valproic acid (VPA) and lamotrigine (LTG) in epileptic children. MATERIAL AND METHODS We administered VPA (102) and LTG (102) to 204 children with epilepsy. Blood samples were collected before the morning dose. Serum concentration of LTG was measured by high-performance liquid chromatography (HPLC). Serum VPA concentration was tested by fluorescence polarization immunoassay. UGT2B7 A268G, C802T, and G211T polymorphisms, as well as UGT1A4 L48V polymorphism, were assayed by direct automated DNA sequencing after PCR. Evaluation of efficacy was conducted using the Engel method. RESULTS The adjusted serum concentration of VPA was 4.26 μg/mL per mg/kg and LTG was 1.56 μg/mL per mg/kg. Multiple linear regression analysis revealed that VPA or LTG adjusted concentration showed a good linear relation with sex and age. UGT2B7 A268G and C802T polymorphisms were demonstrated to affect the serum concentration of VPA (F=3.147, P=0.047; F=22.754, P=0.000). UGT1A4 L48V polymorphism was not related with the serum concentration of LTG (F=5.328, P=0.006). In the efficacy analysis, we found that C802T polymorphism exerted strong effects on efficacy of VPA (χ²=9.265, P=0.010). L48V polymorphism also showed effects on efficacy of LTG (χ²=17.397, P=0.001). CONCLUSIONS UGT2B7, UGT1A4 polymorphisms play crucial roles in metabolism of VPA and LTG.

Purpose: Lamotrigine (LTG) is used to treat epilepsy. The variability of LTG pharmacokinetics among individuals may be attributed to polymorphisms in the genes of uridine diphosphate glucuronosyltransferases (UGTs) 1A4 and UGT2B7 and/or combination with other drugs. In this study, we evaluated the association between LTG concentrations and patient characteristics such as genetic polymorphisms and the co-administration of antiepileptic drugs., Methods: We recruited 122 patients with epilepsy. LTG concentrations were measured in blood samples from each patient under steady-state condition. We assessed the influence of multiple factors on LTG concentrations and derived a formula for predicting LTG concentrations using multiple linear regression analysis., Results: We derived a formula to predict LTG concentrations that considers the daily dose of LTG, body weight, valproic acid concentration, phenytoin co-administration, and the co-administration of phenobarbital and/or carbamazepine as well as UGT1A4 142T>G and UGT2B7 -161C>T polymorphisms (adjusted coefficients of determination R (2) = 0.734). Furthermore, we used this formula to reveal a strong positive correlation between measured and predicted LTG concentrations (r (2) = 0.76, p < 0.001)., Conclusion: We derived a formula that will be useful in clinical practice for predicting LTG concentrations in patients with epilepsy.

Generic substitution of antiepileptic drugs (AEDs) is still a matter of controversy and concern among clinicians and patients. We aimed to assess intrasubject variation in plasma concentrations of lamotrigine (LTG), levetiracetam (LEV) and topiramate (TPM) after generic substitution compared with a stable brand-name drug regimen in a population of patients with epilepsy. A retrospective analysis was performed on prospectively collected and stored data from our therapeutic drug monitoring (TDM) database for the years 2009-2014. The main outcome variable was the proportion of patients who, after switching from branded to generic formulations, showed a greater than ±20% change in AED plasma concentrations compared to the proportion of control patients showing a change in AED plasma concentrations of the same extent while receiving stable branded formulations over repeated TDM tests. Fifty patients on LTG, 27 on LEV and 16 on TPM showing at least one TDM test while receiving generic products fulfilled the inclusion/exclusion criteria for the analysis and were compared with 200 control patients for LTG, 120 for LEV and 80 for TPM. The proportion of patients showing an intrasubject change greater than ±20% in AED plasma concentrations was similar in the brand name vs generic group compared with the control one for LTG (22% vs 33%) and LEV (44% vs 38%), while it was higher in the control group for TPM (41% vs 6%, p<0.01). These are the first data in the literature about the within-patient variation in steady-state plasma concentrations of a series of stable treatments with brand-name AEDs in a real clinical setting. In conclusion, a significant interday variability in intrapatient LTG, LEV and TPM plasma concentrations can be observed even in patients stabilized with the same brand name product over time. This suggests that any change in plasma AED concentration and possible related clinical effects after generic substitution may be not necessarily related to the switch. Our results should be confirmed by large, prospective, blinded, randomized controlled studies in people with epilepsy., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Aim: Patients receiving lamotrigine therapy frequently use paracetamol concomitantly. While one study suggests a possible, clinically relevant drug-drug interaction, practical recommendations of the concomitant use are inconsistent. We performed a systematic pharmacokinetic study in healthy volunteers to quantify the effect of 4 day treatment with paracetamol on the metabolism of steady-state lamotrigine., Methods: Twelve healthy, male volunteers participated in an open label, sequential interaction study. Lamotrigine was titrated to steady-state (100 mg daily) over 36 days, and blood and urine sampling was performed in a non-randomized order with and without paracetamol (1 g four times daily). The primary endpoint was change in steady-state area under the plasma concentration-time curve of lamotrigine. Secondary endpoints were changes in total apparent oral clearance, renal clearance, trough concentration of lamotrigine and formation clearance of lamotrigine glucuronide conjugates., Results: Co-administration of lamotrigine and paracetamol decreased the steady-state area under the plasma concentration-time curve of lamotrigine by 20% (95% CI 10%, 25%; P < 0.001) from 166 to 127 μmol l(-1) . Concomitant administration of paracetamol increased the formation clearance of lamotrigine glucuronide conjugates by 45% (95% CI 18%, 79%, P = 0.005) from 1.7 to 2.8 l h(-1) , while the trough value of lamotrigine was reduced by 25% (95% CI 12%, 36%, P = 0.003) from 5.3 to 3.9 μmol l(-1) ., Conclusion: Paracetamol statistically significantly induced steady-state lamotrigine glucuronidation, resulting in a 20% decrease in total systemic exposure and a 25% decrease in trough value of lamotrigine. This interaction may be of clinical relevance in some patients., (© 2015 The British Pharmacological Society.)

Antiepileptic drugs (AEDs) are a diverse group of pharmacological agents used in the treatment of epileptic seizures. Over the past several decades some new AEDs, including lamotrigine (LTG), levetiracetam (LVA), oxcarbazepine (OXC), topiramate (TOP), and zonisamide (ZNS), have become widely used. This chapter describes a very simple and rapid liquid chromatography-tandem mass spectrometry method for simultaneous quantitation of LVA, ZNS, LTG, TOP, and MHD in human serum. The method requires a very small amount of serum (50 μL) for multiple drug measurements and has a total analysis time of 4 min that makes it well suited for routine clinical analysis of several drugs simultaneously. The imprecision (CVs) measured at various concentrations across the analytical measurement range (AMR) are less than 7% for all analytes. The AMR for each analyte is as follows: LVA (1-100 μg/mL), ZNS (0.8-80 μg/mL), TOP (0.5-50 μg/mL), and 0.6-60 μg/mL for LTG and MHD.

Purpose: The present study aimed to compare the serum LTG levels during the early-/mid-follicular (low estradiol) and mid-luteal (high estradiol) phases of the physiologic menstrual cycle., Method: In a cross-sectional study, 20 women with epilepsy were recruited. Participants had been on monotherapy with LTG for at least two months. All the subjects had normal menstrual cycles. Blood samples for each patient were taken whilst fasting during the early-/mid-follicular (Days 3-5) and mid-luteal phases (Days 20-24). All samples were analyzed in batched assays. A comparison of the serum LTG levels was carried out using the Mann-Whitney U test Data were analyzed with the SPSS program, version 16 (SPSS Inc., Chicago, IL), p-values below 0.05 were considered significant., Results: The mean serum LTG levels for the early-/mid-follicular and mid-luteal phases were 4.28±2.76 mg/ml (SD) and 3.86±2.06 mg/ml (SD), respectively. There was no statistically significant difference in serum LTG level between the (low estradiol) early-/mid-follicular and (high estradiol) mid-luteal phases in our patients (p-value=0.23)., Conclusion: The serum level of LTG does not alter significantly during the menstrual cycle., (Copyright © 2015 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.)

Purpose: To investigate the impact of valproic acid (VPA) and genetic polymorphism of the major metabolizing enzyme (UGT1A4, UGT2B7) of lamotrigine (LTG) and VPA on LTG concentration in Chinese epileptic children., Methods: Three single nucleotide polymorphisms (UGT1A4*3, UGT2B7 -161C > T and UGT2B7*2) were analyzed by polymerase chain reaction-restriction fragment length polymorphism or direct DNA sequencing. The concentrations of LTG and VPA were measured by high-performance liquid chromatography (HPLC) and fluorescence polarization immunoassay, respectively. The adjusted concentration of LTG was defined as the concentration-to-dose-ratio (CDRLTG). Data analysis was performed using IBM SPSS Statistics 21.0., Results: A total of 56 patients treated with LTG as monotherapy and 158 patients treated with LTG plus VPA were included in this study. In the polytherapy group, LTG concentration showed a good linear relationship with gender, age, daily LTG dose, VPA concentration, and UGT1A4*3 polymorphism, but had no relationship with the polymorphism of UGT2B7 -161C > T or UGT2B7*2. Moreover, LTG concentration and CDRLTG for the UGT1A4*3 were higher compared to UGT1A4*1 (LTG: 7.24 ± 3.51 vs 5.26 ± 3.27 μg/mL, p = 0.001; CDRLTG: 2.75 ± 1.02 vs 2.14 ± 0.96 μg/mL per mg/kg, p < 0.001, respectively). In the monotherapy group, there was no statistical difference between UGT1A4*3 and UGT1A4*1 in LTG concentration or CDRLTG. The patients in the polytherapy group were divided into two subgroups according to VPA concentration (lower/higher: 10-50/50-125 μg/mL). CDRLTG values of the patients carrying the UGT1A4*3 genotype were higher compared to UGT1A4*1*1 (2.86 ± 1.03 vs 2.22 ± 0.94 μg/mL per mg/kg, p = 0.001) only when the VPA concentration was higher., Conclusions: UGT1A4*3 polymorphism had an effect on LTG concentration only with VPA co-administration, and the effect was remarkable when VPA concentration was higher.

Case (description): We report the case of a 38-year-old woman treated with lamotrigine who experienced multi-organ dysfunction. The patient received the drug at the dose of 100 mg per day. One week later, the treatment was suspended because of an extensive body rash. Twenty-four hours later, the patient appeared drowsy and stuporous and was hospitalized. On the fifth day, the patient was admitted with a clinical picture of acute multi-organ failure in our Institute, where, she, despite the support of vital functions with vasoactive drugs, continuous hemofiltration and ventilation with oxygen, died. Serum lamotrigine concentration was measured 110 h after its last dose and the drug resulted to be still present at 1 mg/L. The patient was homozygous for the UGT1A4-70C and UGT2B7-161C alleles and heterozygous for the UGT2B7-372A>G polymorphism. Regarding ABCB1 the patient showed the 3435CC, 2677GT and 1236CT genotypes., Conclusion: Our results may suggest a role of the UGT2B7-372A>G polymorphism in this reaction.

A classic 2-period crossover bioavailability study was conducted to evaluate the relative and absolute bioavailability of immediate-release (IR) and extended-release (XR) lamotrigine formulations under steady-state conditions in elderly patients with epilepsy. On treatment days, each subject's morning dose (IR or XR lamotrigine) was replaced with an intravenous 50-mg dose of stable-labeled lamotrigine. Lamotrigine concentrations were measured at 13 points between 0 and 96 hours. XR and IR lamotrigine formulations were similar with respect to steady-state area under the concentration-time curve from 0 to 24 hours (AUC0-24 h ss), average concentration (Cavg, ss), and trough concentration (Cτ, ss). A 33% lower fluctuation in concentrations with XR was observed relative to IR lamotrigine. The time to peak concentration (Tmax, ss) was delayed for XR lamotrigine (3.0 vs 1.3 hours) with lower peak concentration (15% lower). The absolute bioavailability for IR and XR formulations was 73% and 92%, respectively. The formulations were bioequivalent with respect to AUC0-24 h ss, Cτ, ss, and Cavg, ss indicating that it may be possible to switch directly from IR to XR lamotrigine without changes in the total daily dose., (© 2015, The American College of Clinical Pharmacology.)

Introduction: Lamotrigine is licensed for treatment of epilepsy and prevention or at least delay of depressive episodes in bipolar disorder. The accepted therapeutic reference range (TRR) of lamotrigine for anticonvulsant treatment is 3 000-14 000 ng/ml. This TRR is often used for the therapy of bipolar disorders as well. This work presents serious doubts about this approach., Methods: KONBEST, a large TDM database containing patients' characteristics including diagnoses, doses, comedication and serum concentrations, was analyzed. Out of a total of 3 459 lamotrigine samples, 360 patients suffered from bipolar disorder. 82 of them benefitted from therapy with lamotrigine as judged by the clinical global impression of improvement (CGI-I) scale. Patients with a score of minimally (3), much (2) or very much improved (1) were considered as responders., Results: The recommended lamotrigine maintenance dose for bipolar disorder is 200 mg/day; the doses prescribed in our samples ranged from 25 to 450 mg/day. Only 32 concentrations (39.0%) fitted into the TRR recommended for therapy of epilepsy; 50 (61.0%) did not reach it, none exceeded it. The lowest concentration was 177 ng/ml, the highest 11 871 ng/ml. A mean lamotrigine serum concentration of 3 341±2 563 ng/ml (̅x±SD) was detected in the patients who benefitted., Discussion: The authors conclude that in bipolar disorder lower lamotrigine serum concentrations lead to therapeutic benefit., (© Georg Thieme Verlag KG Stuttgart · New York.)

Background: Lamotrigine is an effective anticonvulsant drug used in the treatment of epilepsy. It has a narrow therapeutic range, a large inter and intra-individual pharmacokinetic variability and some concentration-dependent side effects., Aim: The aim of this study was to develop and validate a new method for lamotrigine quantitation in plasma using HPLC with UV/visible detection., Methods: A rapid HPLC-UV method was developed for the determination of lamotrigine in plasma. All solvents used were HPLC grade., Results: After liquid-liquid extraction, chromatographic separation was achieved using an RP 18 (250 mm) column. The mobile phase was composed of acetonitrile and 0.1 M potassium dihyrogenophosphate (25/75) (v/v). Barbital sodium was used as internal standard. This technique was linear over the 2 μg/mL to 50 μg/mL range (r= 0.99). Detection and quantification limits were 0.07 μg/mL and 0.21 μg/mL, respectively. Within-day coefficient of variation (13.37 to 16 %) and day-to-day coefficients of variation (15.68 to 16.63 %) at three different concentrations. Under these conditions, each analysis required no longer than 10 min. We finally evaluated the plasma concentrations of lamotrigine in Tunisian patients treated with this drug., Conclusion: The results found are similar to those previously described and the developed method is repeatable and reproducible. It can be used for clinical applications.

Lamotrigine is a safe anti-epileptic drug among pregnant and lactating women. Some concerns exist regarding the safety of lamotrigine during breastfeeding and related neonatal complications. In this brief review, this matter was evaluated and discussed. In this review study, the medical literature available in search databases such as Embase, Scopus, PubMed, and Medline and even also local medical search engines were evaluated. The results indicated that lamotrigine is a safe anti-epileptic drug for breastfeeding women with rare and usually mild adverse effects among neonates exposed to high milk concentration of this drug and its metabolites. However, close periodical monitoring for infants whose mothers are utilizing lamotrigine is recommended to decrease the probability of severe side effects among them.

This study evaluated the influence of concomitant antiepileptic drugs (AEDs) on the plasma concentration of lamotrigine (LTG) in pediatric patients with epilepsy. We retrospectively reviewed 1653 plasma samples from 709 patients (aged 6 months to 16 years) and compared the concentration-to-dose ratio (CD ratio) of LTG among different AED regimens. The median CD ratio of patients receiving LTG monotherapy was 1.25 μg/mL/mg/kg. In patients receiving LTG plus VPA, the CD ratio was increased by about 140%. The CD ratio was elevated from a low VPA concentration (<40 μg/mL) and the increase was VPA concentration-dependent. In contrast, the median CD ratio of patients treated with LTG plus the inducers phenytoin, phenobarbital, and carbamazepine was 0.42, 0.63, and 0.66, respectively, and phenytoin significantly reduced the CD ratio in comparison with phenobarbital or carbamazepine (p < 0.001). Pediatric patients of all ages beyond infancy showed similar susceptibility to VPA or inducers, but infants had higher CD ratios compared with the other age groups. Among other AEDs, topiramate, ethosuximide, and rufinamide reduced the CD ratio. These findings should be useful for estimating interactions between LTG and concomitant AEDs., (Copyright © 2015 The Japanese Society for the Study of Xenobiotics. Published by Elsevier Ltd. All rights reserved.)

Lamotrigine (LTG) is widely used in the treatment of children with epilepsy. Genetic polymorphisms in genes encoding drug-metabolizing enzymes may be an important source of interindividual variability in LTG metabolism. The aim of this study was to evaluate the effects of genetic polymorphisms of uridine diphosphate glucuronosyltransferase (UGT) 1A4 (UGT1A4) gene on LTG serum concentrations in children with epilepsy. The UGT1A4 142T > G in the coding regions and -219C > T/-163G > A in the 5'-upstream regions were genotyped using polymerase chain reaction amplification followed by direct automated DNA sequencing in 148 patients treated with polytherapy with LTG and valproic acid (VPA). Our data showed that patients carrying the variant UGT1A4 -219C > T/-163G > A genotypes or alleles had significantly higher adjusted LTG concentrations than those carrying the wild-type genotypes or alleles. However, the significant association was abrogated after adjusted by age, body weight, and adjusted VPA concentration. No associations were detected between the UGT1A4 142T > G genotypes or alleles and adjusted LTG concentrations. Taken together, these results suggest that the -219C > T/-163G > A mutations in the 5'-upstream regions of the UGT1A4 gene affect LTG pharmacokinetics, with which is potentially interfered by age, body weight, and concomitant VPA administration., (Copyright © 2014 The Japanese Society for the Study of Xenobiotics. Published by Elsevier Ltd. All rights reserved.)

To establish the HPLC method to examine plasma concentration of lamotrigine and oxcarbazepine. This study set chlorzoxazone as the internal standard, chromatographic column was Column C18 (200×4.6mm, 5um) of DIKMA company, the mobile phase was methanol, water and trifluoroacetic acid, with rate of 40: 60: 0.0005, at a flow rate of 1 mllmin(-1), the detected wavelength was 240 nm. The plasma concentrations of lamotrigine was 0.5-50ug•mL(-1), the standard curve was excellent for Y=0.5511C-0.5669, r=0.9940, average recovery was 91.40%; The plasma concentrations of oxcarbazepine was 0.5-50ugmL-1, the standard curve was good for Y=0.4026C-0.5895, r=0.9925, and the average recovery was 89.59%; The three plasma concentrations of lamotrigine were respectively 25μg•mL(-1), 10 μg•mL(-1) and 2μg•mL(-1) and its five parallel sample for injection RSD were respectively 4.01%, 6.15% and 4.64%; The three plasma concentration of oxcarbazepine were 25μg•mL(-1)-1(-1), 10μg•mL(-1)-1(-1) and 2μg•mL(-1)-1(-1), and its five parallel sample for injection RSD were respectively 3.05%, 4.27% and 9.01%. This method was easy to operate, high recovery and high precision, and was applicable to the clinical detection for plasma concentration of lamotrigine and oxcarbazepine.

Background: Recent concerns have been raised by neurologists and patients with epilepsy regarding the bioequivalence of generic lamotrigine to the brand Lamictal. Bioequivalence studies require the quantification of lamotrigine in human plasma, including in the presence of other drugs, for studies that will use patients with epilepsy rather than healthy volunteers., Methods: Lamotrigine was extracted from plasma through a simple protein precipitation and analyzed by fast liquid chromatography coupled to heated electrospray ionization with tandem mass spectrometric detection. A backflush step to remove interferent accumulation on column was included, and a stable isotope-labeled lamotrigine was used as an internal standard. The method was validated for accuracy, precision, interday and intraday coefficient of variation, specificity, lower limit of detection, lower limit of quantification, linearity, range, instrument precision, freeze-thaw, dilution integrity, and sample stability. Specificity evaluation included consideration of the impact of other antiepileptic drugs., Results: The described method has a linear range of 8-10,000 ng/mL of lamotrigine (r = 0.9999) and a lower limit of detection of 1 ng/mL and a lower limit of quantification of 8 ng/mL. Intraday and interday reproducibility were less than 10.0% relative SD and 10.4% relative SD, respectively, and the percent recovery varied from 96.6% to 109.3% at various lamotrigine concentrations. A backflush step reduced matrix effects and no interference peak from plasma or other antiepileptic drugs were observed., Conclusions: A liquid chromatography-heated electrospray ionization-tandem mass spectrometry method including a backflush step was developed and validated to measure lamotrigine concentration in patient plasma. The method will be applied to bioequivalence studies that compare brand versus generic lamotrigine.

The likelihood of a drug reaction with lamotrigine is increased by dose escalation that is too rapid or drug interactions that increase the concentration of lamotrigine. There is a well-documented interaction between valproic acid and lamotrigine in which lamotrigine levels are increased, subsequently increasing the risk of a drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome. This syndrome is characterized by fever, lymphadenopathy, diffuse maculopapular rash, multivisceral involvement, eosinophilia, and atypical lymphocytes and has a mortality rate of 10-40%. We describe the first case, to our knowledge, of DRESS syndrome that was probably induced by a drug interaction between lamotrigine and ginseng. A 44-year-old white man presented to the emergency department after experiencing a possible seizure. His medical history included two other lifetime events concerning for seizures at ages 14 and 29 years old. After referral to the neurology clinic, he was diagnosed with generalized tonic-clonic seizure disorder, and lamotrigine was started with up-titration according to the drug's package insert to a goal dosage of 150 mg twice/day. The patient had also been taking deer antler velvet and ginseng that he continued during his lamotrigine therapy. On day 43 of therapy, the patient presented to the emergency department with a pruritic rash that had started on his extremities and spread to his torso. He was thought to have experienced a drug reaction to lamotrigine, and the drug was discontinued. Thirteen days later, the patient was admitted from the acute care clinic for inpatient observation due to laboratory abnormalities in the setting of continued rash, headache, and myalgias. His admission laboratory results on that day were remarkable for leukocytosis, with a white blood cell count up to 17.6 × 10(3) /mm(3) , with a prominent eosinophilia of 3.04 × 10(3) /mm(3) ; his liver enzyme levels were also elevated, with an aspartate aminotransferase level of 191 U/L, alanine aminotransferase level 473 U/L, alkaline phosphatase level 465 U/L, and total bilirubin level 1.4 mg/dl. Use of the Drug Interaction Probability Scale indicated that a drug interaction between lamotrigine and ginseng was the probable cause (score of 5). The proposed mechanism of the interaction is ginseng inhibition of the uridine diphosphate glucuronosyltransferase 2B7 enzyme, similar to the mechanism of the interaction with valproic acid. Clinicians should be aware of this probable drug interaction and avoid coadministration of ginseng and lamotrigine or use a more conservative dose titration of lamotrigine for patients who are also taking ginseng., (© 2015 Pharmacotherapy Publications, Inc.)

Background: Therapeutic drug monitoring of antiepileptic drugs in children with epilepsy assists for personalized drug therapy but require numerous patient visits for venous blood sampling. DBS is an alternative matrix applicable to home sampling which can save time and reduce stress for this patient group., Results: A fast LC-MS/MS method for quantification of carbamazepine, lamotrigine and valproic acid based on DBS sampling was developed. The method showed linearity in therapeutically relevant concentration ranges and compatible with unknown volume sampling and expected hematocrit range of the patient group., Conclusion: A LC-MS/MS method for the three most commonly used antiepileptic drugs has been fully validated and clinically applied on DBSs from patients at the neuropediatric clinic at Karolinska University Hospital.

Background: Lamotrigine (LTG) is a widely used antiepileptic-drug (AED) for the treatment of epilepsy. We investigated the effect of AED comedication on LTG clearance in Korean patients with epilepsy., Methods: The authors reviewed the medical charts for all patients≥18years who have received LTG as monotherapy or adjunctive therapy. Data collected included LTG levels, dosage, treatment duration, concomitant AEDs and specific side effects. LTG clearance was estimated according to comedication., Results: A total of 580 blood samples from 548 patients were analyzed. LTG clearance in the enzyme-inducing AED (EIAED) coadministration group was the highest (0.050l/kg/h), followed by the LTG monotherapy group (0.028l/kg/h), the coadministration group of both valproate (VPA) and EIAED (0.024l/kg/h) and the VPA coadministration group (0.018l/kg/h). When LTG was administered with both VPA and EIAED, the multiple EIAED group had higher LTG clearance than the single EIAED group., Conclusions: Concomitant administration of valproate reduced LTG clearance by approximately 35%, while EIAEDs increased LTG clearance by 80%. These relationships indicate the importance of considering the effects of comedication on LTG clearance when determining LTG dosage., (Copyright © 2014 Elsevier B.V. All rights reserved.)

A new, sensitive and fast high-performance liquid chromatography-diode-array detection assay based on microextraction by packed sorbent (MEPS/HPLC-DAD) is herein reported, for the first time, to simultaneously quantify carbamazepine (CBZ), lamotrigine (LTG), oxcarbazepine (OXC), phenobarbital (PB), phenytoin (PHT), and the active metabolites carbamazepine-10,11-epoxide (CBZ-E) and licarbazepine (LIC) in human plasma. Chromatographic separation of analytes and ketoprofen, used as internal standard (IS), was achieved in less than 15min on a C18-column, at 35°C, using acetonitrile (6%) and a mixture (94%) of water-methanol-triethylamine (73.2:26.5:0.3, v/v/v; pH 6.5) pumped at 1mL/min. The analytes and IS were detected at 215, 237 or 280nm. The method showed to be selective, accurate [bias ±14.8% (or ±17.8% in the lower limit of quantification)], precise [coefficient variation ≤9.7% (or ≤17.7% in the lower limit of quantification)] and linear (r(2)≥0.9946) over the concentration ranges of 0.1-15μg/mL for CBZ; 0.1-20μg/mL for LTG; 0.1-5μg/mL for OXC and CBZ-E; 0.2-40μg/mL for PB; 0.3-30μg/mL for PHT; and 0.4-40μg/mL for LIC. The absolute extraction recovery of the analytes ranged from 57.8 to 98.1% and their stability was demonstrated in the studied conditions. This MEPS/HPLC-DAD assay was successfully applied to real plasma samples from patients, revealing to be a cost-effective tool for routine therapeutic drug monitoring of CBZ, LTG, OXC, PB and/or PHT., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Background: Immediate release lamotrigine (LTG-IR) dosing can be limited by peak toxicity. It is thought that peak levels are responsible for some adverse effects such as dizziness, blurred vision, double vision and unsteadiness. At the same time, trough levels may be associated with reduced seizure threshold. The use of extended release lamotrigine (LTG-XR) to replace LTG-IR will be associated with less fluctuation in drug levels-lower peak levels may reduce adverse effects and higher trough levels may improve seizure control. This hypothesis was tested by analyzing seizure control and adverse effects before and after conversion from LTG-IR to LTG-XR in patients who underwent such conversion in 2009-2011., Methods: We searched our patient database to identify patients converted from LTG-IR to LTG-XR for persistent seizures or adverse effects from August 2009 until December 31, 2011. We included only patients who took LTG-IR and LTG-XR for at least 6 months each. We excluded patients with nonepileptic seizures, progressive cause of epilepsy, or not keeping a seizure record. We collected the following parameters: age at conversion, LTG-IR dose and dosing schedule, duration on that dose, LTG-XR dose and dosing schedule, LTG serum level before and after conversion, duration of LTG-XR treatment, seizure frequency before and after conversion, and change in adverse experience profile. We also recorded baseline AEDs and any AED change during the course of the analysis., Results: Fifty five patients (26 female) satisfied the inclusion/exclusion criteria. Their mean age was 45 years (range 23 to 86). Ten were on LTG-IR monotherapy, 24 took LTG-IR plus one other AED, most commonly levetiracetam, and the remaining 21 took LTG-IR plus at least 2 other AEDs. The mean LTG-IR dose was 544 mg/day (range 150-1100 mg/day). The mean LTG-IR serum level was 11.6 (available in 53 patients-range 4.6-21 mcg/ml). Twenty six patients were converted to the same dose and one patient took a mixture of LTG-XR and LTG-IR at the same total daily dose, while 21 had their dose slightly increased and 7 had their dose slightly decreased due to adverse effects. The mean serum level after conversion was 11.8 (available in 49 patients-range 2.6-21.2 mcg/ml). As a result of the conversion, 26 patients (47%) experienced >50% reduction in seizure frequency. There was a 46% median reduction in seizure frequency overall. Seven patients reported improvement in adverse effects., Conclusion: A conversion from LTG-IR to LTG-XR can help improve seizure control in some individuals with drug-resistant epilepsy, in addition to improving tolerability. While it is indicated in individuals experiencing peak adverse effects, it should also be considered in patients who have received incomplete seizure control from LTG-IR., (Copyright © 2014 Elsevier B.V. All rights reserved.)

In recent years, there has been a growth in reports of antiepileptic drugs (AEDs) being misused on their own or in combination with other drugs of abuse in a variety of toxicological case types such as drug abuse, suicide, overdose and drug facilitated crime. To our knowledge, there are no simultaneous quantification methods for the analysis of the most commonly encountered AEDs in postmortem whole blood and clinical plasma/serum samples at the same time. A simple, accurate and cost-effective liquid chromatography-tandem mass spectrometric (LC-MS-MS) method has been developed and validated for the simultaneous quantification of carbamazepine (CBZ) and its metabolite CBZ-10,11-epoxide, eslicarbazepine acetate, oxcarbazepine and S-licarbazepine as a metabolite, gabapentin, lacosamide, lamotrigine, levetiracetam, pregabalin, phenobarbital, phenytoin and its metabolite 5-(p-hydroxyphenyl)-5-phenylhydantoin, retigabine (ezogabine) and its metabolite N-acetyl retigabine, rufinamide, stiripentol, topiramate, tiagabine, valproic acid, vigabatrin and zonisamide in postmortem whole blood, serum and plasma which would be suitable for routine forensic toxicological analysis and therapeutic drug monitoring. All AEDs were detected and quantified within 17 min without endogenous interferences. The correlation coefficient (R(2)) was >0.995 for all AEDs with accuracy ranging from 90 to 113% and precision <13% for all analytes. The recovery ranged from 70 to 98%. No carryover was observed in a blank control injected after the highest standard and the matrix effect was acceptable and ranged from 90 to 120%. The method has been successfully verified using authentic case samples that had previously been quantified using different methods., (© The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Objective: It is sometime difficult to achieve effective blood levels of lamotrigine (LTG) by the methods of administration presented in the product labeling (PL). We highlighted the importance of measuring LTG blood levels, and proposed a method of adjusting the optimum dosage of LTG based on the pharmacokinetic interaction., Method: Four types of maintenance dose of LTG were determined whether LTG was administrated in combination with valproate sodium and/or enzyme-inducing antiepileptic drugs or with agents except for them. This method is compared with the method presented in the PL. We exhibited the clinical course of three patients who took LTG according to our method since the blood levels were not elevated enough by the method shown in the PL., Results: The maintenance dosage described in the PL was lower than that in our methods. The blood levels in these three patients were increased enough to be effective after the therapy by our method., Conclusions: Measuring the LTG blood level is important to create an optimum dosing schedule. Since the maintenance doses of LTG presented in PL may be inappropriate, they should be adequately adjusted by reference to the LTG blood level.

Objective: The pharmacokinetics of lamotrigine (LTG) varies significantly among individuals and particularly among different ethnic groups. This is in part due to the presence of genetic polymorphisms affecting genes that metabolize LTG. UGT1A4 is a major metabolizing enzyme of LTG. The aim of this study was to investigate the effect of two UGT1A4 gene polymorphisms, UGT1A4 (70C > A) and UGT1A4 (142 T > G), on the levels and efficacy of LTG in Han Chinese patients with epilepsy., Methods: The study cohort comprised 106 Han Chinese patients patients with epilepsy who were receiving LTG monotherapy. Blood samples were taken and LTG levels measured. The presence of UGT1A4 (70C > A) and UGT1A4 (142 T > G) was determined. The therapeutic efficacy of LTG at the 1-year time-point was assessed., Results: All patients were homozygous for the CC genotype of UGT1A4 (70C > A), while the distribution of UGT1A4 (142 T > G) varied among patients. Two patients had a single nucleotide deletion at position 127 (UGT1A4 127delA). To evaluate the effect of the UGT1A4 (142 T > G) polymorphism on LTG pharmacokinetics, patients were divided into two groups. Group A included patients with the 142TG or 142GG polymorphism and Group B patients had the 142TT polymorphism. The normalized blood concentration and the efficacy of LTG were higher in Group B patients than in Group A patients (P < 0.05). The two patients with UGT1A4 127delA genotype had extremely high blood levels of LTG, and treatment was discontinued in one of these patients due to a severe LTG-associated rash., Conclusion: Patients with the UGT1A4 142TT polymorphism had a higher blood LTG concentration and better therapeutic efficacy, suggesting that this polymorphism influences LTG activity. The UGT1A4 127delA polymorphism significantly affected LTG levels and increased one of our patient's susceptibility to LTG-related adverse events.

Magnetic molecularly imprinted polymers have been synthesized for the selective preconcentration and trace determination of lamotrigine (LTG) in urine and plasma samples. The magnetic nanoparticles were modified by tetraethyl orthosilicate and 3-methacryloxypropyl trimethoxysilane before imprinting. The magnetic molecularly imprinted polymers were prepared via surface molecular imprinting technique, using Fe3 O4 as a magnetic component, LTG as template molecule, methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as a cross-linker, and 2,2'-azobisisobutyronitrile as a radical initiator in methanol/acetonitrile (50:50, v/v) as the porogen. The obtained sorbent was characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and thermal analysis. Separation of the sorbent from the sample solution was simply achieved by applying an external magnetic field. Determination of the extracted drug was performed by high-performance liquid chromatography with UV detection. Under the optimum extraction conditions, the method detection limits were 0.7 μg/L (based on S/N of 3) for urine samples and 0.5 μg/L for plasma samples. A linear dynamic range of 1-1000 μg/L was obtained for LTF in plasma and urine samples. Finally, the applicability of the proposed method was evaluated by extraction and determination of LTG in urine and plasma samples., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Purpose: The purpose of the study was to examine and describe adjunctive lamotrigine (LTG) pharmacokinetics in paediatric and young adult patients using a nonlinear mixed effects modelling (NONMEM) approach., Methods: The study included 53 patients (age range 3-35 years) who were concomitantly treated with carbamazepine (CBZ) and/or valproic acid (VPA). A total of 70 blood samples corresponding to trough levels were available for analysis. Data were modelled, and the final model was evaluated using NONMEM and auxiliary software tools., Results: The final LTG population model included the effects of concomitant drugs and patient's weight (WT) which stratified the population into three groups: ≤25 kg, >25 to <60 kg and ≥60 kg. Based on the final model, the estimated LTG oral clearance (CL/F) for a typical patient weighing ≤25 kg, >25 to <60 kg or ≥60 kg who was concomitantly treated with CBZ was estimated to be 3.28, 4.23, or 7.15 l/h, respectively. If a patient was concomitantly treated with CBZ + VPA, the CL/F decreased on average by 69.5 % relative to LTG + CBZ co-therapy. VPA was found to decrease the LTG CL/F by 87.6 % compared to co-therapy with only CBZ., Conclusion: The LTG population pharmacokinetic model developed in this study may be a reliable method for individualising the LTG dosing regimen in paediatric and young adult patients on combination therapy during therapeutic drug monitoring.

Objectives: Pregnant women with epilepsy have a significantly increased risk of mortality and morbidity compared to non-pregnant women. At least one in 250 pregnancies is exposed to anti-epileptic drugs (AED). Seizure deterioration occurs in up to a third of pregnant women. AED levels fall in most pregnant women, although it is uncertain that this is responsible for seizure deterioration rather than a hormonal effect. Current practice of AED monitoring is either therapeutic drug monitoring (TDM) or clinical features monitoring (CFM) to adjust the AED dose. We have systematically reviewed the effectiveness of the two monitoring regimens for AEDs, especially lamotrigine, the most commonly used AED in pregnancy on maternal and fetal outcomes., Study Design: We searched MEDLINE (1966-2012), EMBASE (1980-2012) and Cochrane, for relevant citations on the effectiveness of different monitoring strategies on seizure deterioration in pregnant women with epilepsy on lamotrigine. Study selection, quality assessment and data extraction were carried out by two independent reviewers. We calculated the rates of deterioration in seizures with the two strategies and pooled the estimates with random effects meta-analysis., Results: Six observational studies (n=132) evaluated the effectiveness of the two monitoring strategies on pregnant women with epilepsy on lamotrigine. There were no randomised controlled trials. The rate of seizure deterioration was 0.30 (95% CI 0.21-0.41) in women monitored by therapeutic drug monitoring (TDM) compared to 0.73 (95% CI 0.56-0.86) in those receiving clinical feature monitoring (CFM) alone., Conclusion: Evidence based on observational data suggests that monitoring of AED levels in pregnancy reduces seizure deterioration, although the included studies have numerous sources of bias. There is paucity of evidence to make firm recommendations on optimal monitoring of AED drugs in pregnancy. Further research is needed to advise on the best clinical practice in managing AED in pregnancy., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Objective: Little information is available on the need for dosage changes for lamotrigine in pregnant women with bipolar disorder. The authors present new data on serial serum levels of lamotrigine in pregnant patients on lamotrigine monotherapy. They also review the epilepsy literature on use of lamotrigine during pregnancy., Method: Lamotrigine serum samples were obtained from eight mother-infant pairs at different time points during pregnancy and the postpartum period., Results: All of the women were taking lamotrigine throughout pregnancy. Serum-level-to-dose ratios were lower during pregnancy than the postpartum period. Lamotrigine was taken once daily in doses ranging from 100 mg to 300 mg. Three patients had an increase of 50 mg to their daily dose across pregnancy. The change in serum lamotrigine levels in the postpartum period ranged from a 30% decrease to a 640% increase compared with the first level obtained during pregnancy. Level-to-dose ratios obtained within 4 weeks after delivery reflected a mean level 402% greater than the baseline level during gestation. Compared with the third trimester, lamotrigine serum concentration increased an average of 154% within 5 weeks after delivery. The most dramatic increase in lamotrigine serum level early after delivery occurred at 1.5 weeks. The mean infant cord level was 66% of the maternal serum level at delivery. The mean breast-fed infant serum level was 32.5% of the maternal serum levels., Conclusions: The pattern of lamotrigine changes during pregnancy in these women with bipolar disorder was consistent with that described in the epilepsy literature.

Background and Objectives: A high inter-individual variability in the pharmacokinetics of lamotrigine has been observed. Lamotrigine is primarily metabolized by UGT1A4 and UGT2B7, both of which show genetic polymorphisms. Both genetic and non-genetic factors may influence the pharmacokinetics of lamotrigine. The aim of this study was to determine the pharmacokinetic parameters of lamotrigine and to investigate the effect of genetic variants of UGT1A4 and UGT2B7 and various non-genetic factors on its pharmacokinetics., Methods: Four single nucleotide polymorphisms (SNPs; UGT1A4 142 T>G, UGT1A4 70C>T, UGT2B7 372A>G, UGT2B7 -161C>T) were identified using the TaqMan Allelic Discrimination Assay. Data were analyzed using NONMEM. Model evaluation was performed using the bootstrap approach and predictive check., Results: A total of 116 samples were obtained from 75 patients and included in the population analysis. The use of enzyme inducers, valproic acid, and the UGT2B7-161 C>T SNP were found to significantly influence lamotrigine apparent clearance (CL/F). Lamotrigine CL/F in patients carrying the UGT2B7 -161 CT or TT SNP was 18% lower than that in patients carrying the UGT2B7 -161 CC SNP., Conclusion: Both genetic and non-genetic factors were found to influence lamotrigine pharmacokinetics. These factors should be considered when determining lamotrigine dosing. The model presented here could be useful for lamotrigine dose adjustment in clinical practice.

A sensitive and fast high-performance liquid chromatographic method coupled with ultraviolet detection is herein reported for the simultaneous determination of human plasma concentration of six antiepileptic drugs frequently used in clinical practice [phenobarbital (PB), primidone (PRM), phenytoin (PHT), carbamazepine (CBZ), lamotrigine (LTG), oxcarbazepine (OXC)] and some of their main metabolites, carbamazepine-10,11-epoxide (CBZ-E), 10,11-trans-dihydroxy-10,11-dihydrocarbamazepine (trans-diol) and licarbazepine (Lic). Sample preparation consisted of a deproteinization step with methanol followed by a solid-phase extraction procedure. Chromatographic separation was achieved in approximately 15 min on a reversed-phase C18 column using a mobile phase composed by water-methanol-acetonitrile-triethylamine (68.7:25:6:0.3, v/v/v/v; pH 6.5) pumped isocratically at 1.0 mL/min. The detector was set at 237 nm. Calibration curves were linear with regression coefficients greater than 0.992 over the concentration ranges 0.25-100 μg/mL for PB, 0.4-50 μg/mL for PRM, 0.5-50 μg/mL for PHT, 0.1-50 μg/mL for CBZ, LTG and CBZ-E, 0.1-25 μg/mL for OXC, 0.25-10 μg/mL for trans-diol and 0.15-80 μg/mL for Lic. Inter- and intra-day imprecision did not exceed 12.15% and inaccuracy was within ±14.91%. Absolute mean recoveries ranged from 78.49 to 101.04% and no interferences were observed at the retention times of the analytes and internal standard (ketoprofen). This bioanalytical method was successfully applied to real plasma samples from epileptic patients and it seems to be a suitable tool for routine therapeutic drug monitoring and also to support other clinical pharmacokinetic-based studies., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Purpose: The aim of this analysis was to describe the pharmacokinetics of oral lamotrigine (LTG) in Indian epileptic patients using a population pharmacokinetic (PPK) modeling approach to confirm that the PK is similar to that of the Caucasian population, and to evaluate and confirm the impact of covariates predictive of inter-individual variability using a simulation platform., Methods: Blood samples were obtained from 95 patients, and LTG plasma concentrations were determined. Population PK modeling was performed using NONMEM. A one-compartment PK model with first-order absorption and elimination was used to describe the LTG PK. Log-likelihood profiling and normalized prediction distribution errors (NPDE) were used for model evaluation. A simulation study was performed to investigate dose regimens., Results: Clearance (CL) was estimated to be 2.27 L/h with inter-individual variability (IIV) of 29 CV%. Volume of distribution (V) was estimated to be 53.6 L (31 CV% IIV). Body weight and concurrent use of carbamazepine and valproate were identified as significant covariates on clearance. Log-likelihood profiling indicated that parameters could be estimated with adequate precision, and NPDE indicated that the model adequately described the data observed. The simulation study illustrated the impact of carbamazepine and valproate on LTG PK, and negligible differences in PK between Indian and Caucasian patients., Conclusions: This is the first PK analysis of LTG in Indian patients. The population PK model developed adequately described the data observed. Comparison of identified PK parameters with previous PK analyses in Caucasian patients indicates that CL of LTG is similar, while V is somewhat lower compared with Caucasian patients, but this is not expected to lead to relevant differences in PK profiles during steady state.

The correlation between lamotrigine serum concentration, efficacy, and toxicity in children is controversial. The database of the Clinical Pharmacology Laboratory at Assaf Harofeh Medical Center was retrospectively searched to identify lamotrigine serum concentrations in children aged 2-19 years with refractory epilepsy who received lamotrigine as monotherapy or polytherapy from 2007-2010. Data collected included age at epilepsy onset, additional antiepileptic drugs, lamotrigine dose, monthly seizure frequency before and after lamotrigine treatment, and side effects. Sixty blood samples were collected from 42 children aged 10.1 ± 4.9 years (range, 2-20 years). Seizure types included complex partial (n = 28), simple partial (n = 7), absence (n = 2), and generalized tonic-clonic (n = 23). Decreased seizure frequency was observed in 38 (63.3%) patients. No correlation with lamotrigine serum concentration was evident, but seizure frequency was significantly influenced by age and lamotrigine dose. Side effects were reported in 21 (35%) patients. Only diplopia was significantly correlated with lamotrigine serum concentration. Lamotrigine was more effective at lower doses and in older children. Lamotrigine serum concentration correlated significantly with diplopia, but not with other side effects or with clinical efficacy. Overall, lamotrigine is effective and safe in children with refractory epilepsy., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Background: Epilepsy is treated with a variety of anticonvulsants that are often used concomitantly. Therefore, therapeutic drug monitoring is often necessary. Along with clinical and environmental factors, genetic predisposition has been recognized to be relevant for interindividual variability in drug response. Polymorphic transporter proteins such as P-glycoprotein significantly influence pharmacokinetics and bioavailability of many structurally unrelated drugs. The aim of the study was to evaluate the impact of polymorphisms in the P-glycoprotein-encoding gene ABCB1 (C1236T, G2677T/A, C3435T) on antiepileptic drug disposition., Methods: We recruited 222 patients with epilepsy who were prescribed lamotrigine in monotherapy or polytherapy. Lamotrigine plasma concentrations were analyzed and compared with ABCB1 gene variants. The ABCB1 genotyping was performed by real-time polymerase chain reaction methods. The therapeutic drug monitoring was performed by high-performance liquid chromatography-diode array detector (DAD) and immunoassay., Results: A significant correlation was confirmed between lamotrigine concentration and additional drugs (P < 0.001). In the whole group, statistical analysis showed correlations between lamotrigine concentrations and ABCB1 C1236T variants: 10.1 and 6.5 μmol/L for CC versus CT + TT, respectively (P = 0.021), and for dose corrected lamotrigine 0.068 and 0.053 μmol·L·mg, for CC versus CT + TT, respectively (P = 0.017). Analysis of a specific haplotype showed that 1236C-2677G-3435C carriers had higher lamotrigine concentrations than 1236T-2677G-3435T carriers (P < 0.001), followed by 1236T-2677T-3435C carriers (P < 0.001)., Conclusions: ABCB1 C1236T, G2677T/A, C3435T polymorphisms have an influence on lamotrigine serum concentrations.

Background: Newer antiepileptic drugs (AEDs) are widely used in patients with epilepsy. There is still insufficient documentation regarding pharmacokinetic variability of these AEDs in different patient groups., Purpose: The purpose of this study was to compare age and comedication as factors contributing to pharmacokinetic variability between 4 newer AEDs (lamotrigine, levetiracetam, oxcarbazepine, and topiramate) among patients with refractory epilepsy., Methods: Data regarding age, gender, use of AEDs, daily doses, and serum concentration measurements were retrieved from a therapeutic drug monitoring database, from patients admitted to the National Center for Epilepsy, Norway, 2007-2008., Results: In total, 1050 patients were included, 111 younger children (2-9 years), 137 older children (10-17 years), 720 adults (18-64 years), 82 elderly (65-93 years). Fifty percent of the patients were prescribed polytherapy, in 88 different combinations. The interindividual pharmacokinetic variability was extensive, as illustrated by a 10-fold variability in serum concentration compared with dose. Age affected the apparent clearance of levetiracetam to the largest extent, as shown by a 60% increase in younger children and a 40% reduction in the elderly, respectively, compared with adults. Comedication altered the clearance of lamotrigine to the greatest extent ±70% because it is affected by both enzyme inducers and inhibitors. Hepatic enzyme inducers increased the clearance of levetiracetam and topiramate by 25% and oxcarbazepine by 75%. Valproic acid reduced the clearance of topiramate by 25%., Conclusion: Age and comedication are important contributors to pharmacokinetic variability. Age had the greatest impact on levetiracetam, and comedication affected the clearance of each of the 4 AEDs investigated in this study. Pharmacokinetic drug interactions must be carefully considered when multidrug therapies are prescribed. Therapeutic drug monitoring is a valuable tool for individualizing AED therapy.

Introduction: This study evaluates the pharmacokinetic interaction between sertraline and lamotrigine in psychiatric patients., Methods: We identifi ed patients with at least 1 measurement of trough lamotrigine plasma concentration (at steady-state) during lamotrigine therapy and compared dose and plasma concentrations between patients who received lamotrigine with sertraline and patients who received lamotrigine without sertraline., Results: The dose corrected concentration of lamotrigine in patients receiving lamotrigine in combination with sertraline was 60.4 μmol/L × 1,000/mg/day (SD: 31.1) (N = 7) compared to 51.1 μmol/L × 1 000/mg/day (SD: 27.6) (N = 44) in patients using lamotrigine without sertraline (p = 0.42)., Discussion: The slightly slower metabolism of lamotrigine in patients receiving lamotrigine with sertraline compared with those receiving lamotrigine alone is not believed to be of clinical signifi cance. However, due to the limited power, we may have overlooked a diff erence that could be clinically relevant., (© Georg Thieme Verlag KG Stuttgart · New York.)

A highly sensitive, specific and fully validated LC-MS/MS method as per general practices of industry has been developed for estimation of lamotrigine (LAM) with 100 μL of human plasma using flucanozole as an internal standard (IS). The API-4000 LC-MS/MS was operated under the multiple reaction-monitoring mode using electrospray ionization. A simple liquid-liquid extraction process was used to extract LAM and IS from human plasma. The total run time was 2.0 min and the elution of LAM and IS occurred at 1.25 and 1.45 min; this was achieved with a mobile phase consisting of 0.1% formic acid-methanol (20:40:40, v/v) at a flow rate of 0.50 mL/min on a Discovery CN (50 × 4.6 mm, 5 µm) column. The developed method was validated in human plasma with a lower limit of quantitation of 0.1 ng/mL for LAM. A linear response function was established for the range of concentrations 0.1-1500 ng/mL (r > 0.998) for LAM. The intra- and inter-day precision values for LAM met the acceptance as per Food and Drug Administration guidelines. LAM was stable in the set of stability studies, viz. bench-top, autosampler and freeze-thaw cycles. The developed assay method was applied to an oral bioequivalence study in humans., (Copyright © 2011 John Wiley & Sons, Ltd.)

Purpose: Lamotrigine (LTG) is an anti epileptic medication (AEM) for which blood levels are helpful for optimal dosing. In late 2010, patients attending an epilepsy clinic were becoming toxic without obvious cause. This paper reports altered levels without change in regimen and provides unexpected findings., Methods: Patients with elevated LTG blood levels were assessed to determine change in AEM regimen or generic substitution. Method of blood level determination was reviewed and the company (GlaxoSmithKline) contacted regarding change in source of medication., Principal Results: The sample comprised 18 patients; mean age 40±16 years, mean daily LTG dose 493±218 mg. Mean serum LTG concentrations from August 2010 to February 2011 [91.8±17.7 μmolL(-1), range 69.9-133.7 μmolL(-1)] were significantly higher than those from January 2010 to July 2010 [50.3±9.1 μmolL(-1), range 32-60.1 μmolL(-1)), p<0.0001]. All patients received parent product (Lamictal(®)) and the method of LTG blood level determination was unchanged. GlaxoSmithKline confirmed that Lamictal(®) was sourced from a different site., Conclusions: These results indicate that, even using a parent compound, AEM levels can fluctuate if the product source has changed, resulting in toxicity. It also highlights the value of determining AEM levels and the risks attached to generic substitution., (Copyright © 2011 Elsevier B.V. All rights reserved.)