Lacosamide serum concentrations in adult patients with epilepsy: the influence of gender, age, dose, and concomitant antiepileptic drugs

Factors Influencing Plasma Concentrations of Valproic Acid in Pediatric Patients With Epilepsy and the Clinical Significance of CYP2C9 Genotypes in Personalized Valproic Acid Therapy

BACKGROUND

The aim of this study was to investigate the factors affecting plasma valproic acid (VPA) concentration in pediatric patients with epilepsy and the clinical significance of CYP2C9 gene polymorphisms in personalized dosing using therapeutic drug monitoring and pharmacogenetic testing.

METHODS

The medical records of children with epilepsy who underwent therapeutic drug monitoring at our institution between July 2022 and July 2023 and met the inclusion criteria were reviewed. Statistical analysis was performed to determine whether age, sex, blood ammonia, liver function, kidney function, and other characteristics affected the concentration-to-dose ratio of VPA (CDRV) in these patients. To investigate the effect of CYP2C9 polymorphisms on CDRV, DNA samples were collected from patients and the CYP2C9 genotypes were identified using real-time quantitative PCR.

RESULTS

The mean age of 208 pediatric patients with epilepsy was 5.50 ± 3.50 years. Among these patients, 182 had the CYP2C9 *1/*1 genotype, with a mean CDRV (mcg.kg/mL.mg) of 2.64 ± 1.46, 24 had the CYP2C9 *1/*3 genotype, with a mean CDRV of 3.28 ± 1.74, and 2 had the CYP2C9 *3/*3 genotype, with a mean CDRV of 6.46 ± 3.33. There were statistical differences among these 3 genotypes ( P < 0.05). The CDRV in these patients were significantly influenced by age, aspartate aminotransferase, total bilirubin, direct bilirubin, globulin, albumin/globulin ratio, prealbumin, creatinine, and CYP2C9 polymorphisms. In addition, multivariate linear regression analysis identified total bilirubin, direct bilirubin, and CYP2C9 polymorphisms as independent risk factors for high CDRV.

CONCLUSIONS

Liver problems and mutations in the CYP2C9 gene increase VPA levels. This underscores the importance of considering these factors when prescribing VPA to children with epilepsy, thereby enhancing the safety and efficacy of the therapy.

Persistent sodium currents in neurons: potential mechanisms and pharmacological blockers

Persistent sodium current (INaP) is an important activity-dependent regulator of neuronal excitability. It is involved in a variety of physiological and pathological processes, including pacemaking, prolongation of sensory potentials, neuronal injury, chronic pain and diseases such as epilepsy and amyotrophic lateral sclerosis. Despite its importance, neither the molecular basis nor the regulation of INaP are sufficiently understood. Of particular significance is a solid knowledge and widely accepted consensus about pharmacological tools for analysing the function of INaP and for developing new therapeutic strategies. However, the literature on INaP is heterogeneous, with varying definitions and methodologies used across studies. To address these issues, we provide a systematic review of the current state of knowledge on INaP, with focus on mechanisms and effects of this current in the central nervous system. We provide an overview of the specificity and efficacy of the most widely used INaP blockers: amiodarone, cannabidiol, carbamazepine, cenobamate, eslicarbazepine, ethosuximide, gabapentin, GS967, lacosamide, lamotrigine, lidocaine, NBI-921352, oxcarbazepine, phenytoine, PRAX-562, propofol, ranolazine, riluzole, rufinamide, topiramate, valproaic acid and zonisamide. We conclude that there is strong variance in the pharmacological effects of these drugs, and in the available information. At present, GS967 and riluzole can be regarded bona fide INaP blockers, while phenytoin and lacosamide are blockers that only act on the slowly inactivating component of sodium currents.

Development of a UPLC-MS/MS method for the determination of lacosamide and its metabolite and its application to drug-drug interaction

Lacosamide, a third-generation novel antiepileptic drug, was first approved in 2008 as an adjunct to partial seizures. In 2014, the U.S. Food and Drug Administration (FDA) approved it as a single agent for partial seizures. Since epilepsy is a chronic condition, most patients need long-term antiepileptic medicinal products, so it is even more important to consider the drug-drug interactions (DDIs). For the purpose of this experiment, an ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) assay with accuracy and simplicity was optimized and fully validated for the simultaneous quantitative determination of lacosamide and O-Desmethyl-lacosamide (ODL), and DDIs between lacosamide and nisoldipine in vivo and in vitro was researched. The protein was precipitated with acetonitrile, the analytes were eluted with acetonitrile and a 0.1% formic acid solution in a gradient program, and lacosamide, ODL, and lamotrigine (Internal Standard, IS) were successfully separated by chromatography. The findings of the biological analysis revealed that the lower limit of quantification (LLOQ) for lacosamide in samples was 2 ng/mL and the linearity ranged from 2 to 10000 ng/mL. The LLOQ for ODL was 1 ng/mL, while the linearity range for this substance was 1-1,000 ng/mL. In rat liver microsomes (RLM), the LLOQ of ODL was 80 ng/mL and the linear range was 80-40000 ng/mL. The selectivity, stability, matrix effect and recovery rate were all satisfied with the need of quantitative analysis of samples. Then, the UPLC-MS/MS assay was employed successfully on the interactions of lacosamide and nisoldipine in vivo and in vitro. The half-maximal inhibitory concentration (IC50) was 3.412 μM in RLM, where nisoldipine inhibited the metabolism of lacosamide with a mixture of inhibition mechanism. In rat pharmacokinetic experiments, it was found that nisoldipine could significantly change the pharmacokinetic characteristics of lacosamide, including AUC(0-t), AUC(0-∞), Tmax, CLz/F and Cmax, but had no significant effect on ODL. In summary, the UPLC-MS/MS method could accurately and sensitively quantify lacosamide and ODL, and could be used for the interaction between nisoldipine and lacosamide in vivo and in vitro.

Therapeutic drug monitoring of lacosamide among children: is it helpful?

Objective: This study aimed to investigate the efficacy and tolerability of Lacosamide (LCM) in a pediatric population with epilepsy using LCM serum concentration and its correlation to the age of the participants and the dosage of the drug. Methods: Demographic and clinical data were collected from the medical records of children with epilepsy treated with LCM at Shamir Medical Center between February 2019 to September 2021, in whom medication blood levels were measured. Trough serum LCM concentration was measured in the biochemical laboratory using High-Performance Liquid Chromatography (HPLC) and correlated with the administered weight-based medication dosing and clinical report. Results: Forty-two children aged 10.43 ± 5.13 years (range: 1-18) were included in the study. The average daily dose of LCM was 306.62 ± 133.20 mg (range: 100-600). The average number of seizures per day was 3.53 ± 7.25 compared to 0.87 ± 1.40 before and after LCM treatment, respectively. The mean LCM serum concentration was 6.74 ± 3.27 mg/L. No statistically significant association was found between LCM serum levels and the clinical response (p = 0.58), as well as the correlation between LCM dosage and the change in seizure rate (p = 0.30). Our study did not find a correlation between LCM serum concentration and LCM dosage and the gender of the participants: males (n = 17) females (n = 23) (p = 0.31 and p = 0.94, respectively). A positive trend was found between age and LCM serum concentrations (r = 0.26, p = 0.09). Conclusion: Based on the data that has been obtained from our study, it appears that therapeutic drug monitoring for LCM may not be necessary. Nonetheless, further research in this area is needed in the light of the relatively small sample size of the study.

Efficacy and tolerability of lacosamide as adjunctive therapy in patients with focal-onset seizures: an observational, prospective study

PURPOSE

To evaluate the efficacy and tolerability of adjunctive lacosamide (LCM) in patients with focal-onset seizures, with or without combined secondarily generalized seizures.

METHODS

106 patients aged ≥ 16 years were recruited consecutively in this single-center prospective observational study. All patients received LCM as an add-on treatment on the basis of clinical judgement. Seizure frequency, adverse events (AEs) and retention rates were obtained at 3 and 6 months after LCM introduction.

RESULT

The overall response rates were 53.3 and 70.4% after 3 and 6 months, respectively, and the freedom of seizures at the same points was reached at 19 and 26.5%. The retention rates were 99.1% at the 3-month follow-up and 93.3% at the 6-month follow-up. The overall incidence of adverse events was 35.8%. The leading AEs were dizziness (16.98%) and sedation (6.6%).

CONCLUSIONS

Our study confirmed the efficacy and tolerability of adjunctive LCM in Chinese patients in real-life conditions. Based on our treatment experience, a universal maintenance dose of LCM would be needed in Chinese patients.

Therapeutic Drug Monitoring of Lacosamide in Chinese Pediatric Patients with Epilepsy: Efficacy and Factors Influencing the Plasma Concentration

BACKGROUND AND OBJECTIVE

The impact of individual patient variables on drug metabolism is particularly important for antiseizure medication, and lacosamide has not been studied in Chinese pediatric patients with epilepsy. This study evaluated the effects of dose, age, sex, medication time, seizure type, and concomitant enzyme-inducing antiseizure medications (EIASMs) on the plasma concentration of lacosamide.

METHODS

A total of 500 pediatric patients from two hospitals in China were enrolled in this study. Lacosamide plasma concentration was processed using an ultra-performance liquid chromatography assay. Efficacy was evaluated based on the four-grade therapeutic effect criteria developed by the first National Epilepsy Academic Conference of the Chinese Medical Association.

RESULTS

The responder rate to lacosamide therapy was 72.2% (361/500). There was a weaker relationship between the lacosamide daily dose and lacosamide plasma concentration (r = 0.238). Lacosamide plasma concentrations of patients ranged from 1.5 to 19.7 µg/mL, with a mean of 6.9 ± 3.2 µg/mL. The study results showed a significant contribution of age, body mass index, epilepsy duration, medication time, and EIASMs to the lacosamide plasma concentration (p < 0.05). Patients taking concomitant EIASMs with lacosamide had a significantly lower mean lacosamide plasma concentration (5.9 ± 2.6 µg/mL) than patients taking concomitant non-EIASMs (7.5 ± 3.5 µg/mL, p < 0.001).

CONCLUSION

To ensure the clinical efficacy and safety of lacosamide therapy in pediatric patients, it is necessary to monitor the plasma concentration.

Cytochrome P450-mediated antiseizure medication interactions influence apoptosis, modulate the brain BAX/Bcl-XL ratio and aggravate mitochondrial stressors in human pharmacoresistant epilepsy

Polytherapy with antiseizure medications (ASMs) is often used to control seizures in patients suffering from epilepsy, where about 30% of patients are pharmacoresistant. While drug combinations are intended to be beneficial, the consequence of CYP-dependent drug interactions on apoptotic protein levels and mitochondrial function in the epileptic brain remains unclear. We examined the interactions of ASMs given prior to surgery in surgically resected brain tissues and of three ASMs (lacosamide, LCM; oxcarbazepine, OXC; levetiracetam LEV) in isolated brain cells from patients with drug-resistant epilepsy (n = 23). We divided the patients into groups-those who took combinations of NON-CYP + CYP substrate ASMs, NON-CYP + CYP inducer ASMs, CYP substrate + CYP substrate or CYP substrate + CYP inducer ASMs-to study the 1) pro- and anti-apoptotic protein levels and other apoptotic signaling proteins and levels of reactive oxygen species (reduced glutathione and lipid peroxidation) in brain tissues; 2) cytotoxicity at blood-brain barrier epileptic endothelial cells (EPI-ECs) and subsequent changes in mitochondrial membrane potential in normal neuronal cells, following treatment with LCM + OXC (CYP substrate + CYP inducer) or LCM + LEV (CYP substrate + NON-CYP-substrate) after blood-brain barrier penetration, and 3) apoptotic and mitochondrial protein targets in the cells, pre-and post-CYP3A4 inhibition by ketoconazole and drug treatments. We found an increased BAX (pro-apoptotic)/Bcl-XL (anti-apoptotic) protein ratio in epileptic brain tissue after treatment with CYP substrate + CYP substrate or inducer compared to NON-CYP + CYP substrate or inducer, and subsequently decreased glutathione and elevated lipid peroxidation levels. Further, increased cytotoxicity and Mito-ID levels, indicative of compromised mitochondrial membrane potential, were observed after treatment of LCM + OXC in combination compared to LCM + LEV or these ASMs alone in EPI-ECs, which was attenuated by pre-treatment of CYP inhibitor, ketoconazole. A combination of two CYP-mediated ASMs on EPI-ECs resulted in elevated caspase-3 and cytochrome c with decreased SIRT3 levels and activity, which was rescued by CYP inhibition. Together, the study highlights for the first time that pro- and anti-apoptotic proteins levels are dependent on ASM combinations in epilepsy, modulated via a CYP-mediated mechanism that controls free radicals, cytotoxicity and mitochondrial activity. These findings lead to a better understanding of future drug selection choices offsetting pharmacodynamic CYP-mediated interactions.

Anti-inflammatory properties of lacosamide in an astrocyte-microglia co-culture model of inflammation

PURPOSE

Understanding the effects of antiepileptic drugs on glial cells and glia-mediated inflammation is a new approach to future treatment of epilepsy. Little is known about direct effects of the antiepileptic drug lacosamide (LCM) on glial cells. Therefore, we aimed to study the LCM effects on glial viability, microglial activation, expression of gap-junctional (GJ) protein Cx43 as well as intercellular communication in an in vitro astrocyte-microglia co-culture model of inflammation.

METHODS

Primary rat astrocytes co-cultures containing 5% (M5, "physiological" conditions) or 30% (M30, "pathological inflammatory" conditions) of microglia were treated with different concentrations of LCM [5, 15, 30, and 90 μg/ml] for 24 h. Glial cell viability was measured by MTT assay. Immunocytochemistry was performed to analyze the microglial activation state. Western blot analysis was used to quantify the astroglial Cx43 expression. The GJ cell communication was studied via Scrape Loading.

RESULTS

A concentration-dependent incubation with LCM did not affect the glial cell viability both under physiological and pathological conditions. LCM induced a significant concentration-dependent decrease of activated microglia with parallel increase of ramified microglia under pathological inflammatory conditions. This correlated with an increase in astroglial Cx43 expression. Nevertheless, the functional coupling via GJs was significantly reduced after incubation with LCM.

CONCLUSION

LCM has not shown effects on the glial cell viability. The reduced GJ coupling by LCM could be related to its anti-epileptic activity. The anti-inflammatory glial features of LCM with inhibition of microglial activation under inflammatory conditions support beneficial role in epilepsy associated with neuroinflammation.

Ion-Channel Antiepileptic Drugs: An Analytical Perspective on the Therapeutic Drug Monitoring (TDM) of Ezogabine, Lacosamide, and Zonisamide

The term seizures includes a wide array of different disorders with variable etiology, which currently represent one of the most important classes of neurological illnesses. As a consequence, many different antiepileptic drugs (AEDs) are currently available, exploiting different activity mechanisms and providing different levels of performance in terms of selectivity, safety, and efficacy. AEDs are currently among the psychoactive drugs most frequently involved in therapeutic drug monitoring (TDM) practices. Thus, the plasma levels of AEDs and their metabolites are monitored and correlated to administered doses, therapeutic efficacy, side effects, and toxic effects. As for any analytical endeavour, the quality of plasma concentration data is only as good as the analytical method allows. In this review, the main techniques and methods are described, suitable for the TDM of three AEDs belonging to the class of ion channel agents: ezogabine (or retigabine), lacosamide, and zonisamide. In addition to this analytical overview, data are provided, pertaining to two of the most important use cases for the TDM of antiepileptics: drug–drug interactions and neuroprotection activity studies. This review contains 146 references.

Is Therapeutic Drug Monitoring of Lacosamide Needed in Patients with Seizures and Epilepsy?

Lacosamide is an antiepileptic drug (AED) that has linear pharmacokinetics, predictable blood concentrations, and few drug interactions, setting it apart from other AEDs that require vigorous therapeutic drug monitoring (TDM) such as phenytoin and carbamazepine. However, there have been reports of altered lacosamide pharmacokinetics in some populations. The purpose of this review is to determine whether lacosamide pharmacokinetics are altered in certain patient populations, suggesting the need for TDM. A literature search of Medline, Scopus, Embase, and Cochrane trials was conducted on January 3, 2019 (and then updated on September 2, 2019) to search for articles relevant to the TDM or pharmacokinetics of lacosamide. A total of 56 relevant articles were found and included in this review. Dose of lacosamide is linearly correlated with plasma concentrations and efficacy. However, currently there is no well-established reference range. Overall, the recommended reference ranges varied from 2.2 to 20 mg/L. Lacosamide has very few clinically relevant drug-drug interactions; however, there seems to be a significant drug interaction between lacosamide and enzyme-inducer AEDs. Based on available literature, it appears that lacosamide pharmacokinetics may be altered in severe renal dysfunction, in patients on dialysis and with extremes of age. More evidence is currently needed on lacosamide pharmacokinetics in pregnancy and critical illness. While it is not practical to utilize TDM for all patients, TDM may be useful in patients taking enzyme-inducer AEDs, in patients with decreased renal function or on dialysis, and older adults.

Use of Real-World Data and Pharmacometric Modeling in Support of Lacosamide Dosing in Pediatric Patients Under 4 Years of Age

The antiepileptic drug lacosamide (LCM) is approved in the United States and the European Union as monotherapy as well as adjunctive therapy for the treatment of focal seizures in children ≥4 years of age and adults. Using real-world therapeutic drug monitoring data, we performed a pharmacometric analysis for 315 pediatric patients (>1 month to <18 years of age) who received lacosamide as both monotherapy and adjunctive therapy. Population pharmacokinetic modeling was performed using nonlinear mixed-effects modeling with a 1-compartment structural model with linear elimination, where clearance and volume of distribution were allometrically scaled for body weight, with no further need for age-associated maturation functions. A covariate analysis for age, sex, race, and coadministration of other antiepileptic drugs identified phenobarbital and felbamate to significantly increase lacosamide clearance (1.71- and 1.46-fold, respectively). Based on the developed population pharmacokinetic model, simulations were performed in virtual pediatric patients to explore age-associated dose requirements to match lacosamide exposure in patient groups of different age with the exposure achieved in children ≥4 year of age with the weight-based dosing recommendations provided by the US Food and Drug Administration. Based on this approach, our analysis suggested that children ≥3 years of age needed the same dose as recommended by the US Food and Drug Administration for children ≥4 years of age (12 mg/kg/d), while children 1 to 3 years of age may need 13 to 14 mg/kg/d and infants between 1 month and 1 year of age may need 15 to 18 mg/kg/d (based on their actual age) to match the exposure seen in children ≥4 years of age.

Pharmacology of lacosamide: From its molecular mechanisms and pharmacokinetics to future therapeutic applications

Epilepsy is one of the most common brain disorders, affecting more than 50 million people worldwide. Although its treatment is currently symptomatic, the last generation of anti-seizure drugs is characterized by better pharmacokinetic profiles, efficacy, tolerability and safety. Lacosamide is a third-generation anti-seizure drug that stands out due to its good efficacy and safety profile. It is used with effectiveness in the treatment of partial-onset seizures with or without secondary generalization, primary generalized tonic-clonic seizures and off-label in status epilepticus. Despite scarcely performed until today, therapeutic drug monitoring of lacosamide is proving to be advantageous by allowing the control of inter and intra-individual variability and promoting a successful personalized therapy, particularly in special populations. Herein, the pharmacology, pharmacokinetics, and clinical data of lacosamide were reviewed, giving special emphasis to the latest molecular investigations underlying its mechanism of action and therapeutic applications in pathologies besides epilepsy. In addition, the pharmacokinetic characteristics of lacosamide were updated, as well as current literature concerning the high pharmacokinetic variability observed in special patient populations and that must be considered during treatment individualization.

Therapeutic Monitoring of Lacosamide in Japanese Patients With Epilepsy: Clinical Response, Tolerability, and Optimal Therapeutic Range

BACKGROUND

Lacosamide is a novel anticonvulsant that acts by enhancing sodium channel slow inactivation. The aims of this study were to evaluate the influence of concomitant antiepileptic drugs (AEDs) on serum lacosamide concentration and explore the relationship between lacosamide serum concentration and both clinical response and adverse effects.

METHODS

The authors analyzed 649 serum samples from 426 Japanese patients with epilepsy. The concentration-to-dose (CD) ratio of lacosamide was compared among patients on various AED regimens. Clinical information about seizure frequency and adverse events was obtained from clinical records.

RESULTS

In patients who did not receive enzyme-inducing AEDs, the CD ratio (mean ± SD) of lacosamide was 1.84 ± 0.68. By contrast, the CD ratio in patients who received phenytoin, carbamazepine, and phenobarbital was 1.42 ± 0.66 (22.8% lower), 1.46 ± 0.40 (20.7% lower), and 1.36 ± 0.38 (26.1% lower), respectively. Seventy-four patients (17.3%) achieved >50% seizure reduction. The median lacosamide concentration in patients who received and did not receive a sodium channel blocker was 6.6 mcg/mL (26.4 μmol/L) and 8.4 mcg/mL (33.6 μmol/L), respectively. Adverse events, including dizziness, somnolence, diplopia, and anorexia, were reported by 70 patients (16.4%). The incidence rate in patients treated with sodium channel blockers was significantly higher than that in patients not treated with these drugs (21.1% vs. 10.3%; P < 0.005), and the median lacosamide concentration in these patient groups was 5.1 (20.4 μmol/L) and 7.5 mcg/mL (30 μmol/L), respectively.

CONCLUSIONS

Therapeutic drug monitoring of lacosamide is clinically useful because it allows physicians to estimate the extent of drug interactions and adjust the dose in individual AED regimens.

Clinical experience combined with therapeutic drug monitoring of lacosamide

OBJECTIVE

Lacosamide (LCM) is an antiepileptic drug (AED) with insufficient clinical experience in patients with intellectual disability (ID). They often have more severe epilepsy with comorbidities. The objective was to evaluate the efficacy and tolerability of lacosamide (LCM) in patients with refractory epilepsy with and without ID in a real-life setting, taking drug monitoring (TDM) data into account therapeutic.

METHODS

Retrospectively, we identified 344 patients using LCM from the TDM service covering the majority of the country, at the National Center for Epilepsy in Norway (2013-2018). Clinical and TDM data were available for 132 patients.

RESULTS

Forty-four of the 132 patients (33%) had ID. The retention rate was significantly higher in the ID vs the non-ID group after 1 year (84% vs 68%, P < .05). By combining clinical and TDM data, we demonstrated that 37/38 responding patients had serum concentrations above the lower limit of the reference range (>10 µmol/L), and 16/17 with lower concentrations were non-responders. Mean serum concentration/dose ratios were similar in both groups, 0.06 and 0.07 µmol/L/mg. There were no significant differences regarding efficacy and tolerability. The risk of LCM withdrawal was significantly higher when LCM was added to sodium channel blockers, even if the latter was discontinued.

SIGNIFICANCE

Lacosamide was generally well tolerated in patients with drug-resistant epilepsy, where one third had ID, and in these patients the retention rate was higher. The combination of clinical and TDM data could possibly facilitate LCM therapy in these vulnerable patients.

Racial variations in lacosamide serum concentrations in adult patients with epilepsy

Lacosamide (LCM) is a third-generation anti-epileptic drug (AED) for partial-onset epilepsy with minimal hepatic metabolism and drug-drug interactions. The impact of individual patient variables such as race on drug metabolism have been under-reported in AEDs and LCM has not been specifically investigated. Our aim was to assess the role race plays on serum LCM levels in the management of epilepsy. Thus, we retrospectively reviewed patients with focal seizures who received LCM and had LCM levels as part of their routine clinical care in our Level IV Epilepsy Center. Variables including age, race, gender, LCM serum levels, LCM daily dose, and concomitant AEDs were collected and analyzed. A total of 93 patients with 1-3 clinic visits yielded 122 LCM serum levels. African Americans (AA) comprised 62.3% of our serum samples. Daily LCM doses averaged 350 mg/day (range 50-1000 mg/day). Eighty-nine percent of patients took 1-2 other AEDs. Overall, AA patients had lower LCM levels (mean 6.8 μg/mL) compared to White patients (mean of 7.1 μg/mL) (p = .017) even when considering for the daily dose effect (p = .007). Analysis of co-variables did not have significant effect on LCM levels. Overall, AA patients had a weaker relationship between LCM daily dose (adjusted for weight) and serum levels as compared to White patients and require a higher LCM dose per weight to achieve similar levels. Differences in pharmacogenetics may play an important role in these findings and focus on how these variations impact seizure burden.

The adverse-effect profile of lacosamide

Introduction: Lacosamide has been used in epilepsy patients in the United States, Europe and Asia since it was approved by the FDA in 2008. Many patients have benefited from this drug as a new generation of sodium channel blocker. With the worldwide use of this drug, its adverse effects have gradually emerged, especially some rare adverse events.Areas covered: The present review aims to summarize the adverse effects of lacosamide reported in the literature in recent years to promote the safe clinical application of the drug.Expert opinion: In more than 10 years of experience in drug usage, adverse reactions of lacosamide have also been gradually discovered. The review showed that lacosamide is safe and effective in antiepileptic treatment, and its common side effects are dizziness, headache, drowsiness, diplopia, and cardiovascular abnormalities. Skin rashes, hematotoxicity and heart damage, psychological symptoms and suicide risk have also been reported and emphasized.

Therapeutic Drug Monitoring of Antiepileptic Drugs in Epilepsy: A 2018 Update

BACKGROUND

Antiepileptic drugs (AEDs) are the mainstay of epilepsy treatment. Since 1989, 18 new AEDs have been licensed for clinical use and there are now 27 licensed AEDs in total for the treatment of patients with epilepsy. Furthermore, several AEDs are also used for the management of other medical conditions, for example, pain and bipolar disorder. This has led to an increasingly widespread application of therapeutic drug monitoring (TDM) of AEDs, making AEDs among the most common medications for which TDM is performed. The aim of this review is to provide an overview of the indications for AED TDM, to provide key information for each individual AED in terms of the drug's prescribing indications, key pharmacokinetic characteristics, associated drug-drug pharmacokinetic interactions, and the value and the intricacies of TDM for each AED. The concept of the reference range is discussed as well as practical issues such as choice of sample types (total versus free concentrations in blood versus saliva) and sample collection and processing.

METHODS

The present review is based on published articles and searches in PubMed and Google Scholar, last searched in March 2018, in addition to references from relevant articles.

RESULTS

In total, 171 relevant references were identified and used to prepare this review.

CONCLUSIONS

TDM provides a pragmatic approach to epilepsy care, in that bespoke dose adjustments are undertaken based on drug concentrations so as to optimize clinical outcome. For the older first-generation AEDs (carbamazepine, ethosuximide, phenobarbital, phenytoin, primidone, and valproic acid), much data have accumulated in this regard. However, this is occurring increasingly for the new AEDs (brivaracetam, eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, perampanel, piracetam, pregabalin, rufinamide, stiripentol, sulthiame, tiagabine, topiramate, vigabatrin, and zonisamide).

Intravenous lacosamide (LCM) in status epilepticus (SE): Weight-adjusted dose and efficacy

BACKGROUND

Some studies suggest higher efficacy of lacosamide (LCM) in status epilepticus (SE) with higher loading doses; however, this weight-adjusted dose has not been evaluated.

OBJECTIVE

The objective was to evaluate the relationship between loading weight-adjusted dose and efficacy of LCM in SE.

METHODS

A group of patients with SE treated with LCM from Spanish hospitals was examined retrospectively. Demographic data, type of SE, etiology, response rate, last antiepileptic drug (AED) used, treatment line in which LCM was used, total loading dose, and weight-adjusted dose were collected.

RESULTS

One hundred sixty-five cases of SE were collected; 87 (52.7%) patients had nonconvulsive SE. Mean age was 64.2 ± 17.2 and 60.6% (n = 100) were men. Regarding etiology, SE was considered as acute symptomatic in 85 (51.5%), remote symptomatic in 51 (30.9%), progressive symptomatic in 10 (6.1%), and cryptogenic in 19 (11.5%). Lacosamide was used as the third drug in 46.1%, and as a second option in 28%. In 115 patients, clonazepam had been used as the first option, and no benzodiazepines had been administered in the remaining 50. The median loading dose was 400 mg (100-600 mg), and the weight-adjusted dose was 5 mg/kg (3-6 mg/kg). The response rate was 63.3%, and 55.1% responded within the first 12 h. Efficacy was significantly higher in patients who had taken benzodiazepines at LCM loading doses >5.3 mg/kg (p = 0.006). This relationship was maintained independent of using other concomitant AEDs. However, if benzodiazepines were not taken, this relationship was not found.

CONCLUSIONS

In adults with benzodiazepine-resistant SE, the response rate to LCM was higher, with weight-adjusted doses above 5.3 mg/kg.

Immunotherapy by targeting of VGKC complex for seizure control and prevention of cognitive impairment in a mouse model of epilepsy

Epilepsy is a type of refractory neurologic disorder mental disease, which is associated with cognitive impairments and memory dysfunction. However, the potential mechanisms of epilepsy are not well understood. Previous evidence has identified the voltage gated potassium channel complex (VGKC) as a target in various cohorts of patients with epilepsy. In the present study, the efficacy of an antibody against VGKC (anti-VGKC) for the treatment of epilepsy in mice was investigated. A mouse model of lithium-pilocarpine temporal lobe epilepsy was established and anti-VGKC treatment was administered for 30 days. Memory impairment, anxiety, visual attention, inhibitory control and neuronal loss were measured in the mouse model of lithium-pilocarpine temporal lobe epilepsy. The results revealed that epileptic mice treated with anti-VGKC were able to learn the task and presented attention impairment, even a tendency toward impulsivity and compulsivity. It was also exhibited that anti-VGKC treatment decreased neuronal loss in structures classically associated with attentional performance in hippocampus. Mice who received Anti-VGKC treatment had inhibited motor seizures and hippocampal damage as compared with control mice. In conclusion, these results indicated that anti-VGKC treatment may present benefits for improvements of the condition of motor attention impairment and cognitive competence, which suggests that VGKC may be a potential target for the treatment of epilepsy.

An Updated Overview on Therapeutic Drug Monitoring of Recent Antiepileptic Drugs

Given the distinctive characteristics of both epilepsy and antiepileptic drugs (AEDs), therapeutic drug monitoring (TDM) can make a significant contribution to the field of epilepsy. The measurement and interpretation of serum drug concentrations can be of benefit in the treatment of uncontrollable seizures and in cases of clinical toxicity; it can aid in the individualization of therapy and in adjusting for variable or nonlinear pharmacokinetics; and can be useful in special populations such as pregnancy. This review examines the potential for TDM of newer AEDs such as eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, perampanel, pregabalin, rufinamide, retigabine, stiripentol, tiagabine, topiramate, vigabatrin, and zonisamide. We describe the relationships between serum drug concentration, clinical effect, and adverse drug reactions for each AED as well as the different analytical methods used for serum drug quantification. We discuss retrospective studies and prospective data on the serum drug concentration-efficacy of these drugs and present the pharmacokinetic parameters, oral bioavailability, reference concentration range, and active metabolites of newer AEDs. Limited data are available for recent AEDs, and we discuss the connection between drug concentrations in terms of clinical efficacy and nonresponse. Although we do not propose routine TDM, serum drug measurement can play a beneficial role in patient management and treatment individualization. Standardized studies designed to assess, in particular, concentration-efficacy-toxicity relationships for recent AEDs are urgently required.

Perampanel Serum Concentrations in Adults With Epilepsy: Effect of Dose, Age, Sex, and Concomitant Anti-Epileptic Drugs

BACKGROUND

Perampanel (PMP), a noncompetitive α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptor antagonist, is a novel anti-epileptic drug (AED) licensed for the adjunctive treatment of focal and generalized epilepsy. There is limited information on PMP's pharmacokinetics and drug interaction characteristics with concomitant AEDs. We have investigated the effects of PMP dose, age, sex, and coprescribed AEDs on serum PMP concentrations.

METHODS

We used the database of a therapeutic drug monitoring unit at a tertiary epilepsy referral center to identify patients who had PMP as part of their treatment and extracted clinical information from their medical notes. Sera PMP concentrations were determined using liquid chromatography/mass spectroscopy.

RESULTS

In total, 160 sera from 107 patients (66 females) aged 18-70 years and weighing 40-125 kg were identified. They were prescribed a median PMP dose of 6 mg/d (range 2-12 mg/d) and were coprescribed a variety of AEDs, including enzyme-inducing [carbamazepine (CBZ) and oxcarbazepine (OXC)] and enzyme-inhibiting (valproic acid) AEDs. A linear relationship was observed between PMP dose and serum concentrations (r = 0.714, P < 0.0005). Sex and age were found not to influence PMP serum concentration. Enzyme-inducing AEDs dose-dependently decreased PMP concentrations, with CBZ and OXC decreasing mean values by 69% and 37%, respectively. In contrast, although topiramate and phenytoin also decreased mean PMP concentrations by 18% and 13%, respectively, these changes did not achieve statistical significance.

CONCLUSIONS

PMP exhibits a linear dose-concentration relationship, with serum PMP concentrations being age and sex independent. CBZ and OXC can significantly decrease PMP concentrations, probably through an induction of CYP3A4-mediated metabolism.

Acute or chronic use of lacosamide does not alter its distribution between serum and cerebrospinal fluid

OBJECTIVE

The site of action for antiepileptic drugs (AEDs) is within the brain; however, cerebrospinal fluid (CSF) concentration is highly variable. Lacosamide (LCM) is approved by the U.S. Food and Drug Administration (FDA) for treatment of partial-onset seizures in adults, and has linear pharmacokinetics in serum. Penetration across the blood-brain barrier (BBB) is unknown. This study aims to provide additional insights into the pharmacokinetics of LCM.

METHODS

Thirty adults undergoing craniotomy for treatment of intractable epilepsy or brain tumor were recruited and were either taking LCM long term (group 1, n = 15), or were LCM naive, receiving LCM as prophylaxis for surgery (group 2, n = 15). All patients received one intravenous (IV) dose (15 min infusion) immediately prior to craniotomy. CSF and arterial blood were collected simultaneously following craniotomy. LCM concentrations were measured in serum and CSF.

RESULTS

LCM concentration differences between groups 1 and 2 for both CSF and serum were statistically significant (p ≤ 0.0005), but there was no statistically significant difference in CSF/serum ratios (group 1 = 0.726 ± 0.231; group 2 = 0.556 ±0.241; p = 0.0585). LCM concentration in serum correlated positively with CSF concentration in group 1 (Pearson r = 0.8527, p < 0.0001). The time interval between the end of dose delivery and sample collection correlated positively with the CSF/serum ratio for the drug-naive group (Pearson r = 0.6525; p = 0.0084). Treatment with other AEDs did not affect LCM distribution between serum and CSF.

SIGNIFICANCE

Although chronic dosing resulted in higher LCM concentrations in serum and CSF compared to drug-naive patients, the CSF/serum ratio was not affected by LCM pretreatment. These data suggest that LCM serum concentration may reliably predict CSF concentration.

Specific binding of lacosamide to collapsin response mediator protein 2 (CRMP2) and direct impairment of its canonical function: implications for the therapeutic potential of lacosamide

The novel antiepileptic drug lacosamide (LCM; SPM927, Vimpat®) has been heralded as having a dual-mode of action through interactions with both the voltage-gated sodium channel and the neurite outgrowth-promoting collapsin response mediator protein 2 (CRMP2). Lacosamide's ability to dampen neuronal excitability through the voltage-gated sodium channel likely underlies its efficacy in attenuating the symptoms of epilepsy (i.e., seizures). While the role of CRMP2 in epilepsy has not been well studied, given the proposed involvement of circuit reorganization in epileptogenesis, the ability of lacosamide to alter CRMP2 function may prove disease modifying. Recently, however, the validity of lacosamide's interaction with CRMP2 has come under scrutiny. In this review, we address the contradictory reports concerning the binding of lacosamide to CRMP2 as well as the ability of lacosamide to directly impact CRMP2 function. Additionally, we address similarly the contradicting reports regarding the potential disease-modifying effect of lacosamide on the development and progression of epilepsy. As the vast majority of antiepileptic drugs influences only the symptoms of epilepsy, the ability to hinder disease progression would be a major breakthrough in efforts to cure or prevent this debilitating syndrome.

Gender issues in antiepileptic drug treatment

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