Clobazam : in patients with Lennox-Gastaut syndrome

Future Opportunities for Research in Rescue Treatments

Clinical studies of rescue medications for seizure clusters are limited and are designed to satisfy regulatory requirements, which may not fully consider the needs of the diverse patient population that experiences seizure clusters or utilize rescue medication. The purpose of this narrative review is to examine the factors that contribute to, or may influence the quality of, seizure cluster research with a goal of improving clinical practice. We address five areas of unmet needs and provide advice for how they could enhance future trials of seizure cluster treatments. The topics addressed in this article are: (1) unaddressed end points to pursue in future studies, (2) roles for devices to enhance rescue medication clinical development programs, (3) tools to study seizure cluster prediction and prevention, (4) the value of other designs for seizure cluster studies, and (5) unique challenges of future trial paradigms for seizure clusters. By focusing on novel end points and technologies with value to patients, caregivers, and clinicians, data obtained from future studies can benefit the diverse patient population that experiences seizure clusters, providing more effective, appropriate care as well as alleviating demands on health care resources.

Effects of CYP2C19 and P450 oxidoreductase polymorphisms on the population pharmacokinetics of clobazam and N-desmethylclobazam in japanese patients with epilepsy

BACKGROUND

Clobazam (CLB) is a 1,5-benzodiazepine with antiepileptic properties. More than 70% of administered CLB is dealkylated to yield N-desmethylclobazam (N-CLB), a pharmacologically active metabolite, by cytochrome P450 (CYP) 3A4 and CYP2C19. The subsequent inactivation of N-CLB is primarily catalyzed by CYP2C19. Meanwhile, P450 oxidoreductase (POR) is the obligatory electron donor to all microsomal CYP enzymes. The aim of this study was to evaluate the impact of the CYP2C19 and POR genotypes on the pharmacokinetic parameters of CLB and N-CLB.

METHODS

This retrospective study included 85 Japanese patients with epilepsy who were treated with CLB. CYP2C19*2, *3, and P450 oxidoreductase (POR) *28 (rs1057868C>T) polymorphisms were evaluated. A total of 128 steady-state concentrations for both CLB and N-CLB were collected from the patients. A nonlinear mixed-effects model identified the pharmacokinetics of CLB and N-CLB; the covariates included CYP2C19 and POR genotypes, weight, gender, daily CLB dose, and coadministered antiepileptic drugs.

RESULTS

Among the 85 patients, the allele frequencies of CYP2C19*2, CYP2C19*3, and POR*28 were 27.6%, 12.9%, and 41.2%, respectively. A one-compartment model with first-order absorption and/or elimination showed that the clearance of CLB and N-CLB was significantly lower by 18.1% and 84.9%, respectively, in the CYP2C19 poor metabolizers compared with the homozygous extensive metabolizers. The CLB clearance was 44% higher in subjects homozygous for the POR*28 T allele than in those homozygous for the POR*28 C allele, although the genotypes did not affect the N-CLB clearance. The concomitant use of phenobarbital, phenytoin, and zonisamide significantly affected the CLB clearance, whereas that of carbamazepine, phenytoin, and valproic acid affected the N-CLB clearance. The weight also significantly influenced the CLB clearance and volume of distribution of both CLB and N-CLB.

CONCLUSIONS

Our results showed that the CYP2C19 and/or POR genotypes have an impact on the CLB and/or N-CLB clearance. These results suggest that determining the CYP2C19 and/or POR genotypes is helpful for obtaining appropriate serum CLB and N-CLB concentrations and preventing an overdose when starting CLB therapy.