Efficacy of low-dose, add-on therapy of clobazam (CLB) is produced by its major metabolite, N-desmethyl-CLB

We evaluated the efficacy of low-dose, add-on therapy of CLB in adults with refractory epilepsy. 28 patients were included: 12 with temporal lobe epilepsy (TLE), 14 with extratemporal lobe epilepsy (ETLE) and 2 with symptomatic generalized epilepsy (SGE). CLB was added with the initial dose of 2.5 mg/day and increased to the optimal dose (mean, 5.6 mg/day). The mean observation period was 7.9 months. As compared with the baseline period, 14 out of 28 patients (50%) obtained an obviously good seizure control: 6 seizure free and 8 more than 50% of seizure reduction. The 14 patients comprised of 4 TLE, 8 ETLE and 2 SGE. In seizure type analysis, 26% of complex partial seizures (CPS), 64% of simple partial seizures (SPS) and 86% of generalized tonic–clonic seizures (GTC) showed a good control. Blood level of N-desmethyl-CLB in the steady state was higher in seizure-free group of 6 patients, and N-desmethyl-CLB blood level/dose per kg body weight correlated significantly to seizure control (p = 0.0167). Our data show that even in low dose CLB was effective to patients with refractory epilepsy who had higher blood level of N-desmethyl-CLB.