Clobazam add-on therapy for drug-resistant epilepsy.

Background: Epilepsy affects approximately 1% of the population, with up to 30% of patients continuing to have seizures, despite antiepileptic drug treatment. Clobazam is a 1,5-benzodiazepine and is commonly used as an add-on treatment for drug-resistant epilepsy. This review is an updated version of the original Cochrane Review, first published in 2008, and examines the most current literature regarding clobazam as an add-on for drug-resistant epilepsy.

Objectives: To assess the efficacy, effectiveness and tolerability of clobazam as an add-on therapy for drug-resistant generalised-onset and focal-onset seizures, with or without secondary generalisation, in adults and children.

Search Methods: For the latest update, we searched the following databases on 9 October 2018: Cochrane Register of Studies (CRS Web), which includes the Cochrane Epilepsy Group Specialized Register and the Cochrane Central Register of Controlled Trials (CENTRAL), Medline (Ovid) 1946 to 8 October, 2018, ClinicalTrials.gov, and the WHO International Clinical Trials Registry Platform (ICTRP). For some previous updates we also searched SCOPUS, DARE, and BIOSIS Previews, but these are no longer needed. (SCOPUS was searched as a substitute for EMBASE, but randomised and quasi-randomised controlled trials in EMBASE are now included in CENTRAL; DARE ceased operation at the end of March 2015; BIOSIS Previews yielded no relevant items that were not found in the other databases).

Selection Criteria: Randomised trials of add-on clobazam, with adequate methods of allocation concealment, recruiting patients with drug-resistant focal or generalised-onset seizures, with a minimum treatment period of eight weeks.

Data Collection And Analysis: Two review authors independently selected trials for inclusion and extracted relevant data. The following outcomes were assessed: 50% or greater reduction in seizures, seizure freedom, treatment withdrawal and adverse events.

Main Results: Four double-blind, placebo-controlled, cross-over studies, representing 197 participants, were included in the review. All four studies were assessed as having unclear risk of bias due to the unavailability of methodological details. The studies demonstrated significant methodological heterogeneity and differences in outcome measures were noted. Consequently, it was not possible to summarise the data in a meta-analysis. Instead, findings were summarised in a narrative data synthesis, Only two of the studies reported 50% or greater seizure reduction. They respectively reported that 57.7% and 52.4% of participants receiving add-on clobazam experienced a 50% or greater reduction in seizure frequency, although publication bias needs to be considered (2 RCTs, n = 47, very low-quality evidence). Seizure freedom was reported by three of the included studies. Collectively, 27 out of 175 patients were seizure-free during treatment with clobazam (3 RCTs, n = 175, very low-quality evidence). Two studies specifically stated that seizure freedom was not observed in any of the participants receiving add-on placebo. Treatment withdrawal was reported by all four studies. There was a slightly higher incidence of treatment withdrawal associated with receiving clobazam, although the overall incidence was still fairly low (4 RCTs, n = 197, very low-quality evidence). Adverse events were only described in two of the studies, reportedly 36% and 85% of participants experienced one or more adverse events whilst receiving clobazam. The most commonly reported adverse event was drowsiness.

Authors' Conclusions: Clobazam as an add-on treatment may reduce seizure frequency and may be most effective in focal-onset seizures. It is important to recognise that this finding has been derived from very low-quality evidence and from studies judged to have an unclear risk of bias. It remains unclear which population demographic will best benefit from clobazam and over what time-frame. A large-scale, randomised controlled trial, conducted over a greater period of time, incorporating subgroups with differing seizure types, is required to effectively inform clinical practice.