Add-on trial of clobazam in intractable adult epilepsy with plasma level correlations.

Clobazam, a novel benzodiazepine, was used as an add-on agent in 47 adult patients with intractable epilepsy and a variety of seizure types. A greater than 75% reduction in seizure frequency was observed in 42% (18) of the patients and a greater than 50% reduction in 65% (29) of the patients which was sustained over a mean follow-up period of 13.3 (+/- 5.6) months. Nine patients had to discontinue the drug due to minor adverse effects or increased seizures. Possible tolerance developed in 6 patients. Plasma levels of the active metabolite N-desmethylclobazam were linearly related to dosage and appeared to correlate with both therapeutic and toxic responses. Clobazam appears to be a safe and effective add-on antiepileptic for a wide variety of seizure types in intractable epilepsy.