Efficacy of Clobazam as Add-on Therapy for Refractory Epilepsy: Experience at a US Epilepsy Center

Rationale: Clobazam (CLB) has proven efficacy against multiple scizure types. Although available in many countries, it Is not approved by the US Food and Drug Administration. The objective of this study was to evaluate the usage patterns, efficacy, tolerability, and 1-year retention of CLB in patients with refractory epilepsy seen at a tertiary US epilepsy center. Methods: We retrospectively reviewed the use of CLB, I measure of efficacy (6-month seizure freedom), 1-year retention, and tolerability In patients with epilepsy who were prescribed CLB as part of their antiepileptic drug regimen at the Columbia Comprehensive Epilepsy Center over a 5-year period. Results: Two hundred fifty-one patients were prescribed CLB, of which 62 were newly started on CLB at our center during this period (29 male and 33 female subjects; mean age, 43.9 years; range, 8-88 years). Clobazam dose ranged from 5 to 60 mg/d (mean, 23.9 mg/d). The mean number of previous antiepileptic drug trials per patient was 7.7. Of the 62 patients newly started on CLB, 7 patients (11-3% became selzure-free for at least 6 months after introduction of CLB. Binary logistic regression was unable to identify any significant predictors of scizure freedom or CLB retention. Four patients remained seizure-free on CLB for more than 18 months. The Kaplan-Meier 12-month retention curve (n - 54 eligible patients,) showed a 1-year retention rate of 61%. Conclusions: In this population of patients with highly refractory epilepsy at a US center, 11% of patients became seizure-free for at least 6 months after addition of CLB, and the 1-year retention rate was 61%.