Clinically important drug interactions in epilepsy: general features and interactions between antiepileptic drugs

Population Pharmacokinetics and Loading Dose Optimization of Intravenous Valproic Acid in Hospitalized Thai Patients

Our goal is to create a population pharmacokinetic (PK) model and identify the best loading dose (LD) of intravenous valproic acid for hospitalized Thai patients. Data from patients who received intravenous valproic acid and underwent measurement of serum valproic acid concentrations during hospitalization were collected retrospectively. A nonlinear mixed-effects modeling approach was conducted to estimate the PK parameters of valproic acid. Covariates affecting the PK parameters of valproic acid were examined and ranked based on their impact on the model's performance. Monte Carlo simulations of 1000 patients were conducted to estimate the optimal LD of valproic acid. A total of 120 hospitalized patients (51.7% male) with 167 valproic acid concentrations were included in the study. A linear one-compartment model with constant residual error was the best base model. An age-covariate model was the best predictor of valproic acid clearance (CL). The typical values of CL and volume of distribution for valproic acid were 0.77 L/h and 14.56 L, respectively. The LD of 1000-1200 mg intravenous was identified as the pragmatic option as an empirical regimen for hospitalized Thai patients. The recommended time to initiate maintenance dose (MD) is 4-8 h following the LD. The population PK model and optimal LD of valproic acid in hospitalized Thai patients has been established, and it may be advisable to initiate the MD at a later time for the elderly.

Antiseizure Medications and Cardiovascular Events in Older People With Epilepsy

Importance

How epilepsy may promote cardiovascular disease remains poorly understood.

Objective

To estimate the odds of new-onset cardiovascular events (CVEs) over 6 years in older people with vs without epilepsy, exploring how enzyme-inducing antiseizure medications (EIASMs) and traditional cardiovascular risk factors mediate these odds.

Design, Setting, and Participants

This was a prospective cohort study using the comprehensive cohort of the Canadian Longitudinal Study on Aging (CLSA), with 6 years of follow-up (2015-2021, analysis performed in December 2023). The CLSA is an ongoing, national study of 51 338 adults aged 45 to 85 years at baseline who are recruited in Canada. The comprehensive cohort includes 30 097 individuals living near 1 of 11 data collection centers. Participation in the CLSA was voluntary; participation rate was 45%. Among those in the comprehensive cohort, individuals reporting no previous history of CVEs (ie, stroke, transient ischemic attack [TIA], or myocardial infarction [MI]) at baseline were excluded. No other exclusion criteria were applied. A total of 86% of participants completed follow-up.

Exposure

Lifetime history of epilepsy.

Main Outcomes and Measures

The primary outcome was new-onset CVEs over 6 years. Secondary outcomes were new-onset strokes, TIAs, and MIs. Logistic models were fitted for these outcomes as a function of epilepsy, age, sex, household income, and education level. Mediation analyses were conducted for strong EIASM use, weak EIASM use, Framingham score, Physical Activity Scale for the Elderly (PASE) score, and waist to hip ratio.

Results

Among the 30 097 individuals in the comprehensive cohort, a total of 27 230 individuals (mean [SD] age, 62.3 [10.1] years; 14 268 female [52.4%]) were included, 431 with a lifetime history of epilepsy. New-onset CVEs were more likely in epilepsy, with an adjusted odds ratio of 2.20 (95% CI, 1.48-3.27). The proportion of the effect of epilepsy on new-onset CVEs was mediated as follows by each of the following variables: strong EIASM use, 24.6% (95% CI, 6.5%-54.6%), weak EIASM use, 4.0% (95% CI, 0.8%-11.0%), Framingham score, 1.4% (95% CI, -1.6% to 4.5%), PASE score, 3.3% (95% CI, 1.4%-6.8%), and waist to hip ratio, 1.6% (95% CI, 0.4%-3.7%).

Conclusions and Relevance

Results of this cohort study reveal that epilepsy was associated with new-onset CVEs. Nearly one-third of this association can be explained by EIASMs. These findings should be considered when choosing an antiseizure medication for a person at risk for cardiovascular disease.

Patient resuscitated after cardiopulmonary arrest exhibits abnormally increased phenytoin metabolic rate due to unknown factors: a case report

BACKGROUND

Fosphenytoin (FOS) is a prodrug of phenytoin (PHT) with a metabolism that exhibits Michaelis-Menten-type kinetics. Genetic polymorphisms of the metabolic enzymes of PHT make it challenging to predict its plasma concentrations. High plasma PHT concentrations are typically problematic, and several causes have been elucidated. In contrast, cases of patients with low PHT plasma concentrations that did not increase despite the administration of appropriate PHT doses have been reported, and the causes may include changes in plasma protein-binding rates, genetic mutations, and concomitant use of drugs that induce liver enzymes; however, even these factors do not explain the low PHT plasma concentrations in some cases.

CASE PRESENTATION

We encountered the case of a patient with plasma PHT concentrations that were continuously < 0.7 µg/mL after daily use of FOS for seizures that occurred after cardiopulmonary arrest. We analyzed the protein-unbound fraction, urinary metabolites, and related genes to investigate the cause. False negatives due to the measurement method, errors in dosage and administration method, and increased excretion of PHT were excluded. Hepatic metabolic activity of PHT increased to 4.6-6.1 times the normal level. The S/R ratio of 5-(p-hydroxyphenyl)-5-phenylhydantoin-glucuronide, a major PHT metabolite, was normal at 15.2, suggesting increased activities of CYP2C9 and CYP2C19. Furthermore, the protein-unbound fraction of PHT was 5.2-6.9%, CYP2C19*17 was wild type, and there was no concomitant drug use to induce both enzymes.

CONCLUSIONS

The low PHT plasma concentration in this patient was found to be caused by increased hepatic metabolic activity that could not be explained by known factors. Careful monitoring is necessary to consider the possibility of increased hepatic metabolic activity in similar cases.

Presynaptic antiseizure medications - basic mechanisms and clues for their rational combinations

Among clinically highly efficient antiseizure medications (ASMs) there are modifiers of the presynaptic release machinery. Of them, levetiracetam and brivaracetam show a high affinity to the synaptic vesicle protein type 2 A (SV2A), whereas pregabalin and gabapentin are selective ligands for the α2δ1 subunits of the voltage-gated calcium channels. In this paper, we present recent progress in understanding the significance of presynaptic release machinery in the neurochemical mechanisms of epilepsy and ASMs. Furthermore, we discuss whether the knowledge of the basic mechanisms of the presynaptically acting ASMs might help establish a rational polytherapy for drug-resistant epilepsy.

The effect of itraconazole, a strong CYP3A4 inhibitor, on the pharmacokinetics of the first-in-class ACKR3/CXCR7 antagonist, ACT-1004-1239

Cytochrome P450 (CYP) 3A4 is an enzyme involved in the metabolism of many drugs that are currently on the market and is therefore a key player in drug-drug interactions (DDIs). ACT-1004-1239 is a potent and selective, first-in-class ACKR3/CXRC7 antagonist being developed as a treatment for demyelinating diseases including multiple sclerosis. Based on the human absorption, distribution, metabolism, and excretion (ADME) study results, ACT-1004-1239 is predominantly metabolized by CYP3A4. This study investigated the effect of the strong CYP3A4 inhibitor, itraconazole, on the pharmacokinetics of single-dose ACT-1004-1239 in healthy male subjects. In the open-label, fixed-sequence DDI study, a total of 16 subjects were treated. Each subject received a single dose of 10 mg ACT-1004-1239 (Treatment A) in the first period followed by concomitant administration of multiple doses of 200 mg itraconazole and a single dose of 10 mg ACT-1004-1239 in the second period. We report a median of difference in tmax (90% confidence interval, CI) of 0.5 h (0.0, 1.0) comparing both treatments. The geometric mean ratio (GMR) (90% CI) of Cmax and AUC0-∞ was 2.16 (1.89, 2.47) and 2.77 (2.55, 3.00), respectively. The GMR (90% CI) of t1/2 was 1.46 (1.26, 1.70). Both treatments were well-tolerated with an identical incidence in subjects reporting treatment-emergent adverse events (TEAE). The most frequently reported TEAEs were headache and nausea. In conclusion, ACT-1004-1239 is classified as a moderately sensitive CYP3A4 substrate (i.e., increase of AUC ≥2- to <5-fold), and this should be considered in further clinical studies if CYP3A4 inhibitors are concomitantly administered.

Valproate encephalopathy: Case series and literature review

Valproate encephalopathy is one of the unusual and severe but treatable side effect. This research focuses on four female patients who had valproate medication for epilepsy and developed an increased frequency of seizures, exacerbated disruption of consciousness, gastrointestinal problems, cognitive dysfunction, ataxia, and psychobehavioral abnormalities. The patient's symptoms improved over time once sodium valproate was stopped. As a result, when using sodium valproate, one should be aware of the risk of sodium valproate encephalopathy and cease using the medication right once if any of the above symptoms of unknown etiology manifest clinically. We also go over the potential pathogenesis that lead to valproate encephalopathy and the heightened risk of encephalopathy from taking antiepileptic medications together. It was stressed how crucial it is to identify, diagnose, and treat sodium valproate encephalopathy as soon as possible.

Identifying the mechanism of action of the Kv7 channel opener, retigabine in the treatment of epilepsy

Epilepsy is characterized by recurrent epileptic seizures caused by high levels of neuronal excitability in the brain. Voltage-sensitive K+ channels (Kv) of the Kv7 (KCNQ) family encoded by the KCNQ gene are involved in a wide range of cellular processes, i.e., KCNQ2 and KCNQ3 channels mediate M-currents to inhibit neuronal excitability and reduce transmitter release throughout the nervous system. Thus, as a positive allosteric modulator (or opener) of KCNQ channels, retigabine has been the only clinically approved anti-seizure medication that acts on the KCNQ channels. This review discusses the biochemical mechanisms about how retigabine acts on Kv7 channels, significance in neuronal pathophysiology, preclinical efficacy, and clinical stage of development. Additional efforts are being made to emphasize the possible benefits and drawbacks of retigabine compared to currently available medications for treatment-resistant epilepsy.

Population pharmacokinetics of topiramate in Chinese children with epilepsy

OBJECTIVE

Topiramate, a broad-spectrum antiepileptic drug, exhibits substantial inter-individual variability in both its pharmacokinetics and therapeutic response. The aim of this study was to investigate the influence of patient characteristics and genetic variants on topiramate clearance using population pharmacokinetic (PPK) models in a cohort of Chinese pediatric patients with epilepsy.

METHOD

The PPK model was constructed using a nonlinear mixed-effects modeling approach, utilizing a dataset comprising 236 plasma concentrations of topiramate obtained from 181 pediatric patients with epilepsy. A one-compartment model combined with a proportional residual model was employed to characterize the pharmacokinetics of topiramate. Covariate analysis was performed using forward addition and backward elimination to assess the influence of covariates on the model parameters. The model was thoroughly evaluated through goodness-of-fit analysis, bootstrap, visual predictive checks, and normalized prediction distribution errors. Monte Carlo simulations were utilized to devise topiramate dosing strategies.

RESULT

In the final PPK models of topiramate, body weight, co-administration with oxcarbazepine, and a combined genotype of GKIR1-UGT (GRIK1 rs2832407, UGT2B7 rs7439366, and UGT1A1 rs4148324) were identified as significant covariates affecting the clearance (CL). The clearance was estimated using the formulas CL (L/h) = 0.44 × (BW⁄11.7)0.82 × eOXC for the model without genetic variants and CL (L/h) = 0.49 × (BW⁄11.7)0.81 × eOXC × eGRIK1-UGT for the model incorporating genetic variants. The volume of distribution (Vd) was estimated using the formulas Vd (L) = 6.6 × (BW⁄11.7). The precision of all estimated parameters was acceptable. Furthermore, the model demonstrated good predictability, exhibiting stability and effectiveness in describing the pharmacokinetics of topiramate.

CONCLUSION

The clearance of topiramate in pediatric patients with epilepsy may be subject to the influence of factors such as body weight, co-administration with oxcarbazepine, and genetic polymorphism. In this study, PPK models were developed to better understand and account for these factors, thereby improving the precision and individualization of topiramate therapy in children with epilepsy.

A Comprehensive Review of Emerging Trends and Innovative Therapies in Epilepsy Management

Epilepsy is a complex neurological disorder affecting millions worldwide, with a substantial number of patients facing drug-resistant epilepsy. This comprehensive review explores innovative therapies for epilepsy management, focusing on their principles, clinical evidence, and potential applications. Traditional antiseizure medications (ASMs) form the cornerstone of epilepsy treatment, but their limitations necessitate alternative approaches. The review delves into cutting-edge therapies such as responsive neurostimulation (RNS), vagus nerve stimulation (VNS), and deep brain stimulation (DBS), highlighting their mechanisms of action and promising clinical outcomes. Additionally, the potential of gene therapies and optogenetics in epilepsy research is discussed, revealing groundbreaking findings that shed light on seizure mechanisms. Insights into cannabidiol (CBD) and the ketogenic diet as adjunctive therapies further broaden the spectrum of epilepsy management. Challenges in achieving seizure control with traditional therapies, including treatment resistance and individual variability, are addressed. The importance of staying updated with emerging trends in epilepsy management is emphasized, along with the hope for improved therapeutic options. Future research directions, such as combining therapies, AI applications, and non-invasive optogenetics, hold promise for personalized and effective epilepsy treatment. As the field advances, collaboration among researchers of natural and synthetic biochemistry, clinicians from different streams and various forms of medicine, and patients will drive progress toward better seizure control and a higher quality of life for individuals living with epilepsy.

Factors influencing community pharmacists' knowledge about women's issues in epilepsy

Background

Previous studies have highlighted instances where pharmacists lacked knowledge regarding women's health issues related to epilepsy.

Objectives

To assess UAE community pharmacists' knowledge, toward women's issues in epilepsy.

Methods

a cross-sectional research method was employed. A team of seven pharmacy students in their final year visited a randomly selected sample of community pharmacies in the UAE and face-to-face interviews were conducted with the pharmacists using a structured questionnaire. The questionnaire includes two parts; Eight questions designed to elicit data about the demographics of the study participants and 12 questions eliciting insights into the participants' knowledge of women's issues in epilepsy.

Results

A total of 412 community pharmacist were recruited in the study. The overall level of knowledge about women's issues in epilepsy was good and the average knowledge score was 81% with a 95% confidence interval (CI) [79.1, 82.7%]. The results of multivariate analysis showed higher knowledge scores in chain pharmacies (OR 1.37; 95% CI 1.12-1.67), Chief pharmacists (OR 1.44; 95% CI 1.01-2.06), Pharmacists in charge (OR 3.46; 95% CI 2.7-4.45), pharmacists with 1-5 Years of experience (OR 2.87; 95% CI 1.71-4.82), pharmacists with 6-10 Years (OR 2.63; 95% CI 1.58-4.38), pharmacists with >10 years (OR 3.13; 95% CI 2.03-4.83), graduation form regional universities (OR 1.37; 95% CI 1.12-1.67), graduation form international universities (OR 1.73; 95% CI 1.36-2.20) and receiving a training on epilepsy (OR 1.36; 95% CI 1.12-1.67).

Conclusion

While the findings reveal an overall promising level of knowledge among community pharmacists regarding the issues faced by women with epilepsy, pinpointing which clinical and demographic factors have the most significant impact on this knowledge would permit the implementation of tailored educational interventions. Workshops and modules targeting the issues faced by women with epilepsy would further raise the knowledge and competence among community pharmacists in this area, ensuring better pharmaceutical care for this population.

Decreased serum concentrations of antiseizure medications in children with drug resistant epilepsy following treatment with ketogenic diet

OBJECTIVE

To examine the potential influence of a ketogenic diet on serum concentrations of antiseizure medications (ASMs) in children with drug resistant epilepsy.

METHODS

We investigated the serum concentrations of ASMs in 25 children with drug resistant epilepsy, 2-13 years of age, treated with a classical ketogenic diet for 12 weeks. The patients were recruited from the National Centre for Epilepsy from August 15th, 2017, to January 24th, 2022. Changes in ASM serum concentrations were analyzed using a mixed effect model analysis. Significance level was set at P < 0.05 for all comparisons.

RESULTS

The participants used 12 different ASMs during the study. The mean number of ASMs was 2.4 (±SD 0.7). None of the participants changed the type or dose of the ASMs during the intervention period. The serum concentrations of clobazam (n = 9, P = 0.002), desmethylclobazam (n = 9, P = 0.010), and lamotrigine (n = 6, P = 0.016) decreased significantly during the dietary treatment. The analytes with the largest reduction in serum concentration after 12 weeks of dietary treatment were clobazam (mean change -38%) and desmethylclobazam (mean change -37%). We found no significant change in the serum concentrations of levetiracetam, topiramate, and valproic acid.

SIGNIFICANCE

We identified a significant decrease in the serum concentrations of clobazam, desmethylclobazam, and lamotrigine following a 12-week ketogenic diet intervention in children with drug resistant epilepsy. An unintended decrease in the serum concentrations of ASMs may render the patient prone to seizures. Measurements of ASM serum concentrations might be useful in patients on a ketogenic diet, especially in patients with lack of efficacy of the dietary treatment.

A pharmacokinetic model of antiseizure medication load to guide care in the epilepsy monitoring unit

OBJECTIVE

Evaluating patients with drug-resistant epilepsy often requires inducing seizures by tapering antiseizure medications (ASMs) in the epilepsy monitoring unit (EMU). The relationship between ASM taper strategy, seizure timing, and severity remains unclear. In this study, we developed and validated a pharmacokinetic model of total ASM load and tested its association with seizure occurrence and severity in the EMU.

METHODS

We studied 80 patients who underwent intracranial electroencephalographic recording for epilepsy surgery planning. We developed a first order pharmacokinetic model of the ASMs administered in the EMU to generate a continuous metric of overall ASM load. We then related modeled ASM load to seizure likelihood and severity. We determined the association between the rate of ASM load reduction, the length of hospital stay, and the probability of having a severe seizure. Finally, we used modeled ASM load to predict oncoming seizures.

RESULTS

Seizures occurred in the bottom 50th percentile of sampled ASM loads across the cohort (p < .0001, Wilcoxon signed-rank test), and seizures requiring rescue therapy occurred at lower ASM loads than seizures that did not require rescue therapy (logistic regression mixed effects model, odds ratio = .27, p = .01). Greater ASM decrease early in the EMU was not associated with an increased likelihood of having a severe seizure, nor with a shorter length of stay.

SIGNIFICANCE

A pharmacokinetic model can accurately estimate ASM levels for patients in the EMU. Lower modeled ASM levels are associated with increased seizure likelihood and seizure severity. We show that ASM load, rather than ASM taper speed, is associated with severe seizures. ASM modeling has the potential to help optimize taper strategy to minimize severe seizures while maximizing diagnostic yield.

Black-Box Warnings of Antiseizure Medications: What is Inside the Box?

Antiseizure medications can cause serious adverse reactions and have deleterious drug interactions that often complicate the clinical management of patients. When the US Food and Drug Administration (FDA) wants to alert healthcare providers and patients about the risk of potentially serious or fatal drug reactions, the FDA requires the manufacturers of these medications to format these warnings within a "black-box" border, and prominently display this box on the first section of the package insert; such warnings are called "black-box warnings (BBWs)". The BBW is a way for the FDA to urge physicians to evaluate patients more rigorously and carefully weigh the risks and benefits, before prescribing medication that has the potential to cause serious adverse reactions, and to formulate a plan for close monitoring during therapy. The FDA BBW provides the extra layer of safety but many healthcare providers fail to comply with these warnings. Currently, there are 26 FDA-approved antiseizure medications in the US market, 38% of which have received BBWs, and most of the antiseizure medications with BBWs are older-generation drugs. Some antiseizure medications have multiple BBWs; for example, valproic acid has three BBWs including hepatotoxicity, fetal risk, and pancreatitis, carbamazepine has BBWs of serious skin and hematological reactions, and felbamate also has two BBWs including hepatic failure and aplastic anemia. The purpose of this review is to provide insight into each BBW received by antiseizure medications and discuss the FDA recommendations for evaluating the drug benefit/risk, and for monitoring parameters before the initiation of and during treatment.

Immune Mechanisms in Epileptogenesis: Update on Diagnosis and Treatment of Autoimmune Epilepsy Syndromes

Seizures and epilepsy can result from various aetiologies, yet the underlying cause of several epileptic syndromes remains unclear. In that regard, autoimmune-mediated pathophysiological mechanisms have been gaining attention in the past years and were included as one of the six aetiologies of seizures in the most recent classification of the International League Against Epilepsy. The increasing number of anti-neuronal antibodies identified in patients with encephalitic disorders has contributed to the establishment of an immune-mediated pathophysiology in many cases of unclear aetiology of epileptic syndromes. Yet only a small number of patients with autoimmune encephalitis develop epilepsy in the proper sense where the brain transforms into a state where it will acquire the enduring propensity to produce seizures if it is not hindered by interventions. Hence, the term autoimmune epilepsy is often wrongfully used in the context of autoimmune encephalitis since most of the seizures are acute encephalitis-associated and will abate as soon as the encephalitis is in remission. Given the overlapping clinical presentation of immune-mediated seizures originating from different aetiologies, a clear distinction among the aetiological entities is crucial when it comes to discussing pathophysiological mechanisms, therapeutic options, and long-term prognosis of patients. Moreover, a rapid and accurate identification of patients with immune-mediated epilepsy syndromes is required to ensure an early targeted treatment and, thereby, improve clinical outcome. In this article, we review our current understanding of pathogenesis and critically discuss current and potential novel treatment options for seizures and epilepsy syndromes of underlying or suspected immune-mediated origin. We further outline the challenges in proper terminology.

Pharmacokinetic Interactions Between Antiseizure and Psychiatric Medications

Antiseizure medications and drugs for psychiatric diseases are frequently used in combination. In this context, pharmacokinetic interactions between these drugs may occur. The vast majority of these interactions are primarily observed at a metabolic level and result from changes in the activity of the cytochrome P450 (CYP). Carbamazepine, phenytoin, and barbiturates induce the oxidative biotransformation and can consequently reduce the plasma concentrations of tricyclic antidepressants, many typical and atypical antipsychotics and some benzodiazepines. Newer antiseizure medications show a lower potential for clinically relevant interactions with drugs for psychiatric disease. The pharmacokinetics of many antiseizure medications is not influenced by antipsychotics and anxiolytics, while some newer antidepressants, namely fluoxetine, fluvoxamine and viloxazine, may inhibit CYP enzymes leading to increased serum concentrations of some antiseizure medications, including phenytoin and carbamazepine. Clinically relevant pharmacokinetic interactions may be anticipated by knowledge of CYP enzymes involved in the biotransformation of individual medications and of the influence of the specific comedication on the activity of these CYP enzymes. As a general rule, these interactions can be managed by careful evaluation of clinical response and, when indicated, individualized dosage adjustments guided by measurement of drugs serum concentrations, especially if pharmacokinetic interactions may cause any change in seizure control or signs of toxicity. Further studies are required to improve predictions of pharmacokinetic interactions between antiseizure medications and drugs for psychiatric diseases providing practical helps for clinicians in the clinical setting.

Fosphenytoin dosing regimen including optimal timing for the measurement of serum phenytoin concentration in pediatric patients

INTRODUCTION

We aimed to evaluate the pediatric fosphenytoin dosing regimen, including optimal timing for the measurement of total serum phenytoin concentration (C_PHT).

METHODS

We retrospectively investigated pediatric patients with status epilepticus or seizure clusters treated with fosphenytoin between April 2013 and March 2018. Two C_PHT measurements were analyzed, one 2-4 h after the loading dose and another before the second dose. Individual pharmacokinetic parameters were estimated using the Bayesian method and were used to simulate C_PHT.

RESULTS

The present study involved 12 pediatric patients; the loading dose of fosphenytoin was 22.1 (17.2-27.2) mg/kg. The C_PHT was 13.4 (8.6-18.9) μg/mL 2-4 h after the loading dose. The C_PHT estimated from individual pharmacokinetic parameters 12 and 24 h after the loading dose was 9.5 (6.7-14.2) and 5.8 (3.7-10.0) μg/mL, respectively. If fosphenytoin was administered at a loading dose of 22.5 mg/kg and a maintenance dose of 5 or 7.5 mg/kg (administered every 12 h, starting 12 h after the loading dose), then the C_PHT on day 8 was estimated to be 5.74 (2.6-15.4) μg/mL at 5 mg/kg and 13.9 (5.7-31.0) μg/mL at 7.5 mg/kg.

CONCLUSIONS

In pediatric patients, a maintenance dose of fosphenytoin should be started 12 h after the loading dose, and a maintenance dose of 5-7.5 mg/kg/dose every 12 h may be better than every 24 h. We recommend measuring C_PHT at 2 and 12 h after the loading dose to simplify and safely adjust the dosage in clinical practice.

Comorbid epilepsy and depression—pharmacokinetic and pharmacodynamic drug interactions

Background: Major depressive disorder may be encountered in 17% of patients with epilepsy and in patients with drug-resistant epilepsy its prevalence may reach 30%. This indicates that patients with epilepsy may require antidepressant treatment.

Purpose: Both pharmacodynamic and pharmacokinetic interactions between antiepileptic (antiseizure) and antidepressant drugs have been reviewed. Also, data on the adverse effects of co-administration of antiepileptic with antidepressant drugs have been added. This article was submitted to Neuropharmacology, a section of the journal Frontiers in Pharmacology.

Methods: The review of relevant literature was confined to English-language publications in PUBMED databases. Table data show effects of antidepressants on the seizure susceptibility in experimental animals, results of pharmacodynamic interactions between antiepileptic and antidepressant drugs mainly derived from electroconvulsions in mice, as well as results concerning pharmacokinetic interactions between these drugs in clinical conditions.

Conclusion: Antidepressant drugs may exert differentiated effects upon the convulsive threshold which may differ in their acute and chronic administration. Animal data indicate that chronic administration of antidepressants could reduce (mianserin, trazodone) or potentiate the anticonvulsant activity of some antiepileptics (fluoxetine, reboxetine, venlafaxine). There are also examples of neutral interactions (milnacipran).

Comparative pharmacokinetics of valproic acid among Pakistani and South Korean patients: A population pharmacokinetic study

Purpose

The pharmacokinetics of valproic acid have been evaluated in a variety of populations however, the comparison in two different populations was yet to be reported. This study is aimed to compare the pharmacokinetics of valproic acid in Pakistani and South Korean patients.

Method

The therapeutic drug monitoring (TDM) data of valproic acid from 92 Pakistani patients with 218 samples was combined with the data of 99 South Korean patients with 335 samples in order to form a pooled dataset of 191 patients with 553 samples. Population pharmacokinetic model was developed on NONMEM® software by using first order conditional estimation method for estimation of pharmacokinetic parameters. The influence of different covariates including ethnicity was evaluated the stepwise covariate modelling. The final model was evaluated for predictive performance and robustness by using goodness of fit plots and bootstrap analysis respectively.

Results

The data was better described by one compartment model with first order elimination. The value for clearance (CL) of valproic in pooled data was 0.931 L/h with 43.4% interindividual variability (IIV) while volume of distribution (Vd) was 16.6 L with 22.3% IIV. In covariate analysis, ethnicity and body weight were significant covariates for CL while body weight was also significant for Vd.

Conclusion

A significant difference in CL of valproic acid among Pakistani and South Korean patients was observed. The model can be used for the dose tailoring of valproic acid based on ethnicity and body weight of Pakistani and South Korean patients.

Why won't it stop? The dynamics of benzodiazepine resistance in status epilepticus

Status epilepticus is a life-threatening neurological emergency that affects both adults and children. Approximately 36% of episodes of status epilepticus do not respond to the current preferred first-line treatment, benzodiazepines. The proportion of episodes that are refractory to benzodiazepines is higher in low-income and middle-income countries (LMICs) than in high-income countries (HICs). Evidence suggests that longer episodes of status epilepticus alter brain physiology, thereby contributing to the emergence of benzodiazepine resistance. Such changes include alterations in GABA_A receptor function and in the transmembrane gradient for chloride, both of which erode the ability of benzodiazepines to enhance inhibitory synaptic signalling. Often, current management guidelines for status epilepticus do not account for these duration-related changes in pathophysiology, which might differentially impact individuals in LMICs, where the average time taken to reach medical attention is longer than in HICs. In this Perspective article, we aim to combine clinical insights and the latest evidence from basic science to inspire a new, context-specific approach to efficiently managing status epilepticus.

Improving epilepsy control among children with cerebral palsy in rural Bangladesh: a prospective cohort-based study

OBJECTIVE

To define the prevalence and seizure subtypes among children with cerebral palsy (CP) in rural Bangladesh and explore barriers to optimum epilepsy control.

DESIGN

Prospective cohort study.

SETTING

The study was conducted in Shahjadpur, a rural subdistrict of Bangladesh.

PARTICIPANTS

Children (<18 years) with CP and epilepsy identified using the Bangladesh CP Register (BCPR) in the study site.

METHODS

Assessments were conducted in three focused epilepsy clinics overseen by a paediatric neurologist between December 2016 and January 2018, with intervening phone and video-conference follow-ups. Details of event type, frequency and medication compliance were collected. Antiepileptic drugs (AEDs) were prescribed based on seizure type, family income, comorbidity and medication availability.

RESULTS

23.4% (170/726) of the BCPR cohort had a clinical diagnosis of epilepsy of whom 166 were assessed. Following the focused epilepsy clinics, 62.0% (103/166) children were clinically determined to have ongoing epileptic seizures. 62.1% (64/103) had generalised onset tonic clonic seizures, 27.2% (28/103) had focal onset seizures with impaired awareness and 10.7% (11/103) had other seizure types. None of the children with prolonged seizures (31/103) had an emergency seizure management plan. Non-epileptic events were being pharmacologically treated as seizures in 18.1% (30/166) children. Financial constraints were the main reason for non-compliance on follow-up.

CONCLUSIONS

Gaps in optimum epilepsy management in rural Bangladesh are amenable to improvement anchored with local healthcare workers. Training and clinical care focused on recognition of common seizure types, seizure mimics and rationalising use of available AEDs can be facilitated by better referral pathways and telehealth support.

Effect of cenobamate on the single-dose pharmacokinetics of multiple cytochrome P450 probes using a cocktail approach in healthy subjects

This study was designed to evaluate the effects of cenobamate, an antiseizure medication for focal seizures, on the pharmacokinetics of cytochrome P450 probes (bupropion, CYP2B6; midazolam, CYP3A4/5; warfarin, CYP2C9; and omeprazole, CYP2C19) in healthy subjects. Probes were administered alone on days 1 (bupropion) and 7 (midazolam/warfarin/omeprazole), and with cenobamate 100 mg/day on day 69 (midazolam) and cenobamate 200 mg/day on days 99 (bupropion) and 105 (midazolam/warfarin/omeprazole). No significant interaction was concluded if 90% confidence intervals (CIs) for geometric mean ratios (GMRs) for area under the curve (AUC) and maximum concentration of CYP substrates and/or their metabolites were within the no‐effect interval (0.80–1.25). When co‐administered with cenobamate 100 mg/day, AUC from time of administration up to the time of the last quantifiable concentration (AUC_0–last) GMR (90% CIs) for midazolam was 0.734 (0.647–0.832). When co‐administered with cenobamate 200 mg/day, AUC_0–last GMRs (90% CI) for midazolam, bupropion, S‐warfarin, and omeprazole were 0.277 (0.238–0.323), 0.615 (0.522–0.724), 1.14 (1.10–1.18), and 2.07 (1.44–2.98), respectively. Co‐administration of cenobamate with midazolam and bupropion probes led to values that were outside and below the no effect boundary, indicating that cenobamate induces the CYP3A4/5 and CYP2B6 enzymes. Co‐administration of cenobamate led to omeprazole values which were outside and above the no‐effect boundary, but with high variability, suggesting that cenobamate may moderately inhibit CYP2C19 activity. No effect on CYP2C9 was observed with the cenobamate and warfarin combination. Co‐administration of cenobamate with these probes drugs was well‐tolerated. In this study, 200 mg/day cenobamate moderately induced CYP3A4/5 (dose‐dependently; 100 mg/day was a weak inducer), was a weak inducer of CYP2B6, moderately inhibited CYP2C19, and had a negligible effect on CYP2C9.

Cardiac Sodium Channel Blockade Due to Antiepileptic Drug Combination

Drugs that inhibit voltage-dependent sodium channels are commonly used to treat epilepsy. Old and novel antiepileptic drugs are used either as monotherapy or in combination to control epilepsy. For a long time, carbamazepine has been used as the first choice for the treatment of simple and complex partial seizures. In the USA, lacosamide was approved in October 2008 as an adjunctive treatment for partial-onset seizures. We describe the effect of two sodium channel blockers on the heart of a patient with epilepsy.

LEARNING POINTS

Approximately 30% of patients with epilepsy require combination therapy with antiepileptic drugs for seizure reduction.Lacosamide and carbamazepine are both sodium channel blockers but exert their effects through different mechanisms.Electrocardiogram monitoring is necessary when lacosamide and carbamazepine are used together as this combination may predispose to seizures, conduction abnormalities and dysrhythmia.

Selection of antiseizure medications for first add-on use: A consensus paper

INTRODUCTION

When monotherapy used alone or sequentially fails to achieve seizure control, a trial of combination therapy may be considered.

OBJECTIVE

To define optimal criteria to guide choice of an antiseizure medication (ASM) for use as first add-on.

METHODS

A standardized Delphi procedure was applied to produce a list of consensus statements. First, an Expert Board consisting of 5 epileptologists agreed on a set of 46 statements relevant to the objective. The statements were then finalized through an iterative process by a Delphi Panel of 84 Italian pediatric and adult neurologists with expertise in the management of epilepsy. Panel members provided anonymous ratings of their level of agreement with each statement on a 9-point Likert scale.

RESULTS

Consensus, defined as agreement by at least 80% of Panel members, was reached for 36 statements. Medication-related factors considered to be important for drug selection included efficacy, tolerability and safety, interaction potential, mechanism of action, and ease of use. The need to optimize adherence and to tailor drug selection to individual characteristics was emphasized.

CONCLUSIONS

Choice of an ASM for first add-on requires consideration of many factors, many of which also apply to choose initial treatment. Factors more specifically relevant to add-on use include drug interaction potential and the preference for an ASM with a different mechanism of action.

A systematic review and meta-analysis of the association of ABCC2/ABCG2 polymorphisms with antiepileptic drug responses in epileptic patients

PURPOSE

Accumulating evidence indicates that genetic polymorphisms in ATP-binding cassette superfamily members, such asABCC2 and ABCG2, alter responses to antiepileptic drugs (AEDs); however, this evidence is controversial and inconclusive. To provide strong evidence of the association between common polymorphisms in ABCC2 and ABCG2 and AED responses in patients with epilepsy, we performed a systematic review and meta-analysis.

METHODS

A literature search of electronic databases (PubMed, EBSCO, Ovid and the China National Knowledge Infrastructure) was performed. To evaluate the association of genetic polymorphisms inABCC2 and ABCG2 and risk of AED treatment, we calculated pooled odds ratios (ORs) and 95 % confidence intervals (CIs) using a fixed- or random-effect model.

RESULTS

A significant association of theABCC2 rs717620 polymorphism with resistance to AEDs was found in the overall pooled populations (homozygous comparison: OR = 1.77, 95 % CI, 1.27-2.48; dominant model: OR = 1.23, 95 % CI, 1.06-1.43; recessive model: OR = 1.75, 95 % CI, 1.28-2.40) and Asians (dominant model: OR = 1.21, 95 % CI, 1.03-1.42; recessive model: OR = 1.80, 95 % CI, 1.30-2.50). Using a recessive model, a similarly significant association of ABCC2 rs3740066 with AED resistance was observed in the overall pooled populations (OR = 2.29, 95 % CI, 1.44-3.64) and Asians (OR = 2.53, 95 % CI, 1.56-4.08). However, ABCC2 rs2273697, ABCG2 rs2231137 and rs2231142 were not found to be associated with AED responsiveness.

CONCLUSION

This meta-analysis suggests thatABCC2 rs717620 and rs3740066 are risk factors that predict responses to AEDs in epileptic patients.

Interactions among Lacosamide and Second-Generation Antiepileptic Drugs in the Tonic-Clonic Seizure Model in Mice

Combination therapy with two or three antiseizure medications (ASMs) is sometimes a preferred method of treatment in epilepsy patients. (1) Background: To detect the most beneficial combination among three ASMs, a screen test evaluating in vivo interactions with respect to their anticonvulsant properties, was conducted on albino Swiss mice; (2) Methods: Classification of interactions among lacosamide (LCM) and selected second-generation ASMs (lamotrigine (LTG), pregabalin (PGB), oxcarbazepine (OXC), and topiramate (TPM)) was based on the isobolographic analysis in the mouse maximal electroshock-induced seizure (MES) model. Interactions among LCM and second-generation ASMs were visualized using a polygonogram; (3) Results: In the mouse MES model, synergy was observed for the combinations of LCM + TPM + PGB and LCM + OXC + PGB. Additivity was reported for the other combinations tested i.e., LCM + LTG + TPM, LCM + LTG + PGB, LCM + LTG + OXC, and LCM + OXC + TPM in this seizure model. No adverse effects associated with triple ASM combinations, containing LCM and second-generation ASMs were observed in mice; (4) Conclusions: The combination of LCM + TPM + PGB was the most beneficial combination among the tested in this study, offering synergistic suppression of tonic-clonic seizures in mice subjected to the MES model. Both the isobolographic analysis and polygonogram method can be recommended for experimental epileptology when classifying interactions among the ASMs.

Pharmacokinetic drug interactions between antiseizure medications and drugs for comorbid diseases in children with epilepsy

Introduction: Nearly 80% of children with epilepsy have one or more chronic comorbidities that require specific drug treatments in several cases. Drug-drug interactions (DDIs) between antiseizure medications (ASMs) and all other drugs (NON-ASMs) used to treat comorbid diseases may have serious consequences.Areas covered: All potential DDIs between 27 ASMs and all NON-ASMs used for oral chronic treatment of those disorders most often comorbid with epilepsy in children were searched for drug compendia. Clinical evidence of the identified DDIs was also searched in the literature. Forty-eight drugs have been identified as potential DDIs with at least one ASM. Most important DDIs are between some ASMs and omeprazole and pantoprazole (drugs for gastrointestinal disorders), ibuprofen and cyclobenzaprine (drugs for musculoskeletal disorders), loratidine, lumacaftor/ivacaftor, montelukast, and theophylline (drugs for respiratory system), levothyroxine, liothyronine and several corticosteroids (systemic hormonal preparations), almotriptan, dihydroergotamine, ergotamine, and several antipsychotics, antidepressants and anxiolytics (drugs for nervous diseases). Clinical evidence of the predicted DDIs was found in a minority of cases.Expert opinion: Treatment of children with epilepsy should be decided considering treatment of both seizures and comorbid diseases and aimed at minimizing the risk of DDIs between ASMs and NON-ASMs.

Characteristics of adverse drug reactions associated with antiepileptics at a tertiary children's hospital in Japan: A retrospective observational cohort study

OBJECTIVE

The aim of this study was to explore the prescription pattern of antiepileptics and the relationship between antiepileptics and adverse drug reactions (ADRs) in a Japanese population.

METHODS

A retrospective observational cohort study was conducted by reviewing the medical records of patients who visited or were admitted to a single tertiary care center between January 2011 and June 2019, were treated with antiepileptics, and developed allergic ADRs associated with these drugs.

RESULTS

In total, 14,230 unique patients received antiepileptics during the study period. Diazepam was the most frequently used antiepileptic drug (74.8 %), followed by phenobarbital (14.3 %), valproic acid (11.4 %), fosphenytoin (10.0 %), and carbamazepine (7.3 %). Although a trend of increasing prevalence of newer generation antiepileptics was noted, most patients are still treated with older generation antiepileptics. Thirty-two (0.22 %) unique patients experienced ADRs associated with antiepileptics, and the antiepileptic drug most frequently associated with ADRs was carbamazepine, at a rate of 1.4 %. Three patients developed Stevens-Johnson syndrome/toxic epidermal necrolysis, in two of which carbamazepine was implicated. Most patients experienced ADRs associated with aromatic antiepileptics (84.4 %) or older generation antiepileptics (81.3 %).

SIGNIFICANCE

This is the first study to assess the relationship between ADRs and antiepileptics at a tertiary care center in Japan. Based on our results, most patients were prescribed older generation antiepileptics, and most ADR events were linked to the administration of drugs in this category; thus, identification of patients at risk of developing ADRs is critical in order to prevent such events.

Cannabidiol for Treating Lennox-Gastaut Syndrome and Dravet Syndrome in Korea

BACKGROUND

For the first time in Korea, we aimed to study the efficacy and safety of cannabidiol (CBD), which is emerging as a new alternative in treating epileptic encephalopathies.

METHODS

This study was conducted retrospectively with patients between the ages of 2-18 years diagnosed with Lennox-Gastaut syndrome (LGS) or Dravet syndrome (DS) were enrolled from March to October 2019, who visited outpatient unit at 3 and 6 months to evaluate medication efficacy and safety based on caregiver reporting. Additional evaluations, such as electroencephalogram and blood tests, were conducted at each period also. CBD was administered orally at a starting dose of 5 mg/kg/day, and was maintained at 10 mg/kg/day.

RESULTS

We analyzed 34 patients in the LGS group and 10 patients in the DS group between the ages of 1.2-15.8 years. In the 3-month evaluation, the overall reduction of seizure frequency in the LGS group was 52.9% (>50% reduction in 32.3% of the cases), and 29.4% in the 6-month evaluation (more than 50% reduction in 20.6%). In DS group, the reduction of seizure frequency by more than 50% was 30% and 20% in the 3-month and 6-month evaluation, respectively. Good outcomes were defined as the reduction of seizure frequency by more than 50% and similar results were observed in both LGS and DS groups. Adverse events were reported in 36.3% of total patients of which most common adverse events were gastrointestinal problems. However, no life-threatening adverse event was reported in both LGS and DS during the observation period.

CONCLUSION

In this first Korean study, CBD was safe and tolerable for use and could be expected to potentially reduce the seizure frequency in pediatric patients with LGS or DS.

Trends in oral anticoagulant co-prescription with antiepileptic drugs among adults with epilepsy, 2010-2018

Treatment considerations for epilepsy patients requiring anticoagulation are changing, and actual prescribing practices have not been characterized. We used the 2010-2018 Optum Clinformatics® Data Mart Database to estimate the annual prevalence and distinguish the patterns of oral anticoagulants (OACs) co-dispensed with antiepileptic drugs (AEDs) among adults with epilepsy. Monotonic trends were assessed using the Spearman rank correlation coefficient (ρ). Multivariable logistic regression models were built to evaluate the associations of sociodemographic characteristics. Among 345,892 adults with epilepsy (56.5% female; median age 61, IQR 46-74) on studied AEDs, the prevalence per thousand of concurrent OACs increased from 58.4 in 2010 to 92.0 in 2018 (OR 1.63, CI 1.58-1.69). Direct-acting oral anticoagulant (DOAC) use rapidly increased from 2010 to 2018 (ρ = 1.00; P < 0.001), with a corresponding decrease in warfarin use (ρ = -0.97; P < 0.001). Among OAC/AED dispensings in 2018, warfarin was more likely to be co-dispensed with potentially interacting, enzyme-inducing antiepileptic drugs (EI-AEDs) versus presumably non-interacting, non-enzyme inducing antiepileptic drugs (OR 1.48, CI 1.38-1.59). Characteristics independently associated with concurrent OAC/EI-AED use included younger age, female sex, white race, net worth <$250 K, and lower education levels. Our findings demonstrate the expanding use and evolving patterns of OAC/AED co-dispensing, and ensuing critical need to further understanding regarding postulated interactions.

Polygonogram with isobolographic synergy for three-drug combinations of phenobarbital with second-generation antiepileptic drugs in the tonic-clonic seizure model in mice

Background

Combination therapy consisting of two or more antiepileptic drugs (AEDs) is usually prescribed for patients with refractory epilepsy. The drug–drug interactions, which may occur among currently available AEDs, are the principal criterion taken by physicians when prescribing the AED combination to the patients. Unfortunately, the number of possible three-drug combinations tremendously increases along with the clinical approval of novel AEDs.

Aim

To isobolographically characterize three-drug interactions of phenobarbital (PB) with lamotrigine (LTG), oxcarbazepine (OXC), pregabalin (PGB) and topiramate (TPM), the maximal electroshock-induced (MES) seizure model was used in male albino Swiss mice.

Materials and method

The MES-induced seizures in mice were generated by alternating current delivered via auricular electrodes. To classify interactions for 6 various three-drug combinations of AEDs (i.e., PB + TPM + PGB, PB + OXC + TPM, PB + LTG + TPM, PB + OXC + PGB, PB + LTG + PGB and PB + LTG + OXC), the type I isobolographic analysis was used. Total brain concentrations of PB were measured by fluorescent polarization immunoassay technique.

Results

The three-drug mixtures of PB + TPM + PGB, PB + OXC + TPM, PB + LTG + TPM, PB + OXC + PGB, PB + LTG + PGB and PB + LTG + OXC protected the male albino Swiss mice from MES-induced seizures. All the observed interactions in this seizure model were supra-additive (synergistic) (p < 0.001), except for the combination of PB + LTG + OXC, which was additive. It was unable to show the impact of the studied second-generation AEDs on total brain content of PB in mice.

Conclusions

The synergistic interactions among PB and LTG, OXC, PGB and TPM in the mouse MES model are worthy of being transferred to clinical trials, especially for the patients with drug resistant epilepsy, who would benefit these treatment options.

Population pharmacokinetics of phenobarbital in Caucasian patients with epilepsy

The present study aimed to establish a population pharmacokinetic (PopPK) model of Phenobarbital (PB) in Caucasian patients with epilepsy included in a Therapeutic Drug Monitoring program. In total, 855 PB serum concentrations (steady-state trough concentrations) were retrospectively collected during routine clinical monitoring of 395 patients over 15 years of age with epilepsy. The PopPK analysis was performed with NONMEM using a non-linear mixed-effect modelling approach. The influence of demographic, anthropometric, treatment, and comedication variables on the apparent clearance (CL/F) of PB were analysed. Goodness of fit plots and the bootstrap method were performed to evaluate the final model. External validation was carried out using an independent group of patients (107 patients, 178 blood samples). A one-compartment model with first-order absorption and elimination successfully described the data. In the final model, CL/F included body surface area (BSA) and comedication with phenytoin (PHT) and valproic acid (VPA), resulting in the following equation: CL/F[L/h]=(0.236+(0.115×(BSA-1.7)))×(0.822^PHT)×(0.711^VPA) The model presents acceptable estimation errors in the parameters of fixed (<12%) and random effects (<13%), and of the shrinkage values (<21%). Internal and external validations demonstrated the good predictability of the final model. A PopPK model of PB in Caucasian patients over 15 years of age was successfully established, which can be used to estimate phenobarbital CL/F. BSA and drug-drug interactions with PHT and VPA should be incorporated into dosing decisions. This PopPK, using Bayesian algorithms, could help establish an optimal dosage regimen in routine patient care.

Potential Pharmacokinetic Drug-Drug Interactions between Cannabinoids and Drugs Used for Chronic Pain

Choosing an appropriate treatment for chronic pain remains problematic, and despite the available medication for its treatment, still, many patients complain about pain and appeal to the use of cannabis derivatives for pain control. However, few data have been provided to clinicians about the pharmacokinetic drug-drug interactions of cannabinoids with other concomitant administered medications. Therefore, the aim of this brief review is to assess the interactions between cannabinoids and pain medication through drug transporters (ATP-binding cassette superfamily members) and/or metabolizing enzymes (cytochromes P450 and glucuronyl transferases).

Convolutional neural network for detection and classification of seizures in clinical data

Epileptic seizure detection and classification in clinical electroencephalogram data still is a challenge, and only low sensitivity with a high rate of false positives has been achieved with commercially available seizure detection tools, which usually are patient non-specific. Epilepsy patients suffer from severe detrimental effects like physical injury or depression due to unpredictable seizures. However, even in hospitals due to the high rate of false positives, the seizure alert systems are of poor help for patients as tools of seizure detection are mostly trained on unrealistically clean data, containing little noise and obtained under controlled laboratory conditions, where patient groups are homogeneous, e.g. in terms of age or type of seizures. In this study authors present the approach for detection and classification of a seizure using clinical data of electroencephalograms and a convolutional neural network trained on features of brain synchronisation and power spectrum. Various deep learning methods were applied, and the network was trained on a very heterogeneous clinical electroencephalogram dataset. In total, eight different types of seizures were considered, and the patients were of various ages, health conditions and they were observed under clinical conditions. Despite this, the classifier presented in this paper achieved sensitivity and specificity equal to 0.68 and 0.67, accordingly, which is a significant improvement as compared to the known results for clinical data. Graphical abstract.

Influence of genetic variants and antiepileptic drug co-treatment on lamotrigine plasma concentration in Mexican Mestizo patients with epilepsy

Genetic and nongenetic factors may contribute to lamotrigine (LTG) plasma concentration variability among patients. We simultaneously investigated the association of UGT1A1, UGT1A4, UGT2B7, ABCB1, ABCG2, and SLC22A1 variants, as well as antiepileptic drug co-treatment, on LTG plasma concentration in 97 Mexican Mestizo (MM) patients with epilepsy. UGT1A4*1b was associated with lower LTG dose-corrected concentrations. Patients with the UGT2B7-161T allele were treated with 21.22% higher LTG daily dose than those with CC genotype. Two novel UGT1A4 variants (c.526A>T; p.Thr185= and c.496T>C; p.Ser166Leu) were identified in one patient. Patients treated with LTG + valproic acid (VPA) showed higher LTG plasma concentration than patients did on LTG monotherapy or LTG + inducer. Despite the numerous drug-metabolizing enzymes and transporter genetic variants analyzed, our results revealed that co-treatment with VPA was the most significant factor influencing LTG plasma concentration, followed by UGT1A4*1b, and that patients carrying UGT2B7 c.-161T required higher LTG daily doses. These data provide valuable information for the clinical use of LTG in MM patients with epilepsy.

Polygonogram and isobolographic analysis of interactions between various novel antiepileptic drugs in the 6-Hz corneal stimulation-induced seizure model in mice

Pharmacotherapy with two antiepileptic drugs in combination is usually prescribed to epilepsy patients with refractory seizures. The choice of antiepileptic drugs in combination should be based on synergistic cooperation of the drugs with respect to suppression of seizures. The selection of synergistic interactions between antiepileptic drugs is challenging issue for physicians, especially, if 25 antiepileptic drugs are currently available and approved to treat epilepsy patients. The aim of this study was to determine all possible interactions among 5 second-generation antiepileptic drugs (gabapentin (GBP), lacosamide (LCM), levetiracetam (LEV), pregabalin (PGB) and retigabine (RTG)) in the 6-Hz corneal stimulation-induced seizure model in adult male albino Swiss mice. The anticonvulsant effects of 10 various two-drug combinations of antiepileptic drugs were evaluated with type I isobolographic analysis associated with graphical presentation of polygonogram to visualize the types of interactions. Isobolographic analysis revealed that 7 two-drug combinations of LEV+RTG, LEV+LCM, GBP+RTG, PGB+LEV, GBP+LEV, PGB+RTG, PGB+LCM were synergistic in the 6-Hz corneal stimulation-induced seizure model in mice. The additive interaction was observed for the combinations of GBP+LCM, GBP+PGB, and RTG+LCM in this seizure model in mice. The most beneficial combination, offering the highest level of synergistic suppression of seizures in mice was that of LEV+RTG, whereas the most additive combination that protected the animals from seizures was that reporting additivity for RTG+LCM. The strength of interaction for two-drug combinations can be arranged from the synergistic to the additive, as follows: LEV+RTG > LEV+LCM > GBP+RTG > PGB+LEV > GBP+LEV > PGB+RTG > PGB+LCM > GBP+LCM > GBP+PGB > RTG+LCM.

Pharmacodynamic interactions of antiepileptic drugs: From bench to clinical practice

BACKGROUND

Approximately 50% of patients do not achieve seizure control with antiepileptic drug (AED) monotherapy, and polytherapy, with more than one AED, is often required. To date, no evidence-based criteria on how to combine AEDs exist.

OBJECTIVE

This narrative review aimed to provide critical findings of the available literature about the role of pharmacodynamic AEDs' interactions in patients whose epilepsies were treated with polytherapy.

METHODS

Electronic databases, Medical Literature Analysis and Retrieval System Online (MEDLINE) and Excerpta Medica dataBASE (EMBASE), were systematically searched to identify relevant studies on pharmacodynamic AEDs' interactions in patients with epilepsy.

RESULTS AND CONCLUSION

Most data on AED combinations are coming from animal models and preclinical studies. Combining AEDs with different mechanisms of actions seems to have greater effectiveness and lower risk of adverse event development. Conversely, the combination of AEDs may cause pharmacodynamic synergistic effects that may result in not only increased efficacy but also more adverse effects. Despite some AED associations that have been proven to be effective in specific epilepsy/seizure type (e.g., phenobarbital+/phenytoin for tonic seizures and ethosiximide + valproate for absences; lamotrigine + valproate for various epilepsy/seizure types), no clear and definitive evidence exists about AED combinations in humans. Examples of pharmacodynamic interactions that possibly explain the synergistic effects on efficacy or adverse effects include the combination between vigabatrin or pregabalin and sodium channel blockers (supra-additive antiseizure effect) and lacosamide combined with other sodium channel blockers (infra-additive antiseizure effect and neurotoxicity synergistic). The pharmacodynamic lamotrigine-valproate interaction is also supported by synergistic adverse events. Therefore, well-designed double-blind prospective studies recruiting a sufficient number of patients possibly with a crossover design and carefully ascertain the role of pharmacokinetic interactions and variations of AEDs' levels in the blood are needed.

First add-on perampanel for focal-onset seizures: An open-label, prospective study

Objectives

This study aimed to determine the efficacy and safety of perampanel added to monotherapy in patients with focal‐onset seizures, with or without secondarily generalized tonic‐clonic seizures.

Materials & Methods

In this multicentre, open‐label trial, enrolled patients were treated with perampanel monotherapy. During a 12‐week titration period, perampanel was incrementally increased by 2 mg/d over ≥2‐week intervals. Patients then entered a 24‐week maintenance period. The primary objective was to investigate the 50% responder rate in total seizure frequency, with 75% and 100% responder rates as secondary objectives. Treatment‐emergent adverse events (TEAEs) and adverse drug reactions were recorded. A post hoc analysis was performed to investigate the effect of titration speed and different concomitant AEDs on the efficacy and safety of perampanel.

Results

Of the 85 patients analysed, seizure reductions of 50%, 75% and 100% were observed in 80.0% (95% confidence interval [CI]: 69.9‐87.9), 71.8% (95% CI: 61.0‐81.0) and 47.1% (95% CI: 36.1‐58.2) during the maintenance period, respectively. The 50%, 75% and 100% response rates in patients with secondarily generalized tonic‐clonic seizures were 87.5% (95% CI: 61.7‐98.5), 87.5% (95% CI: 61.7‐98.5) and 75.0% (95% CI: 47.6‐92.7), respectively. The most common TEAEs were dizziness (50.0%), somnolence (9.8%) and headache (8.8%). The efficacy outcomes and safety profile of perampanel were more favourable with slow titration and relatively consistent when stratified by concomitant AEDs.

Conclusions

Perampanel was effective and well tolerated as a first add‐on to monotherapy in patients with focal‐onset seizures, with or without secondarily generalized seizures.

Why we urgently need improved epilepsy therapies for adult patients

PURPOSE

Up to a third of patients with epilepsy suffer from recurrent seizures despite therapeutic advances.

RESULTS

Current epilepsy treatments are limited by experiential data from treating different types of epilepsy. For example, we lack evidence-based approaches to efficacious multi-drug therapies or identifying potentially serious or disabling adverse events before medications are initiated. Despite advances in neuroscience and genetics, our understanding of epilepsy pathogenesis and mechanisms of treatment-resistance remains limited. For most patients with epilepsy, precision medicine for improved seizure control and reduced toxicity remains a future goal.

CONCLUSION

A third of epilepsy patients suffer from ongoing seizures and even more suffer from adverse effects of treatment. There is a critical need for more effective and safer therapies for epilepsy patients with frequent comorbitidies, including depression, anxiety, migraine, and cognitive impairments, as well as special populations (e.g., women, elderly). Advances from genomic sequencing techniques may identify new genes and regulatory elements that influence both the depth of the epilepsies' roots within brain circuitry as well as ASD resistance. Improved understanding of epilepsy mechanisms, identification of potential new therapeutic targets, and their assessment in randomized controlled trials are needed to reduce the burden of refractory epilepsy. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

Effect of newer anti-epileptic drugs (AEDs) on the cognitive status in pentylenetetrazol induced seizures in a zebrafish model

Epilepsy is marked by seizures that are a manifestation of excessive brain activity and is symptomatically treatable by anti-epileptic drugs (AEDs). Unfortunately, the older AEDs have many side effects, with cognitive impairment being a major side effect that affects the daily lives of people with epilepsy. Thus, this study aimed to determine if newer AEDs (Zonisamide, Levetiracetam, Perampanel, Lamotrigine and Valproic Acid) also cause cognitive impairment, using a zebrafish model. Acute seizures were induced in zebrafish using pentylenetetrazol (PTZ) and cognitive function was assessed using the T-maze test of learning and memory. Neurotransmitter and gene expression levels related to epilepsy as well as learning and memory were also studied to provide a better understanding of the underlying processes. Ultimately, impaired cognitive function was seen in AED treated zebrafish, regardless of whether seizures were induced. A highly significant decrease in γ-Aminobutyric Acid (GABA) and glutamate levels was also discovered, although acetylcholine levels were more variable. The gene expression levels of Brain-Derived Neurotrophic Factor (BDNF), Neuropeptide Y (NPY) and Cyclic Adenosine Monophosphate (CAMP) Responsive Element Binding Protein 1 (CREB-1) were not found to be significantly different in AED treated zebrafish. Based on the experimental results, a decrease in brain glutamate levels due to AED treatment appears to be at least one of the major factors behind the observed cognitive impairment in the treated zebrafish.