Sustained efficacy and long-term safety of oxcarbazepine: One-year open-label extension of a study in refractory partial epilepsy

Purpose: To evaluate the long-term efficacy, tolerability, and safety of oxcarbazepine (OXC) in medically refractory partial epilepsy. Methods: This study is the open-label extension phase that followed a multicenter, randomized, double-blind, dose-response clinical study of OXC monotherapy in patients with medically refractory partial epilepsy. We analyzed the efficacy, tolerability, and safety of OXC during the first 48 weeks of open-label therapy. To evaluate efficacy, we compared the change in seizure frequency throughout the 48 weeks of treatment with OXC with the baseline seizure frequency that preceded the double-blind phase of the core study by an intent-to-treat and completer analysis. Safety and tolerability were evaluated by using an intent-to-treat analysis. Results: Of the 87 patients enrolled in the double-blind study, 76 patients participated in the open-label extension phase. Fifty-five (72%) patients completed 48 weeks of open-label treatment on a median OXC dose of 2,400 mg/day. Based on an intent-to-treat analysis, the median reduction in seizure frequency was 47% (p = 0.0054); the 50 and 75% responder rates were 46.1 and 25.0%, respectively, with 6.6% of patients remaining seizure free. The completer analysis yielded comparable efficacy results. OXC was well tolerated, with 13% of patients exiting because of adverse events. The six most common adverse events, irrespective of their causal relation to OXC, were dizziness, headache, fatigue, diplopia, nausea, and rash. For the most part, these adverse events tended to be transient. Conclusions: The efficacy of OXC is sustained with good safety and tolerability profiles during long-term treatment of patients with medically refractory partial epilepsy.