Purpose: The goal of the study was to evaluate the safety and efficacy of a broad oxcarbazepine (OXC) dosage range (600, 1200, and 2400 mg/d) as adjunctive therapy for uncontrolled partial seizures and to determine the relationship between trough plasma 10-monohydroxy derivative concentrations and OXC safety and efficacy.
Methods: This multinational, multicenter, randomized, 28-week, double-blind, placebo-controlled, four-arm, parallel-group trial enrolled 694 patients aged 15-65 years with uncontrolled partial seizures with or without secondarily generalized seizures. The primary efficacy variable was percentage change in seizure frequency per 28 days relative to baseline.
Results: The median reduction in seizure frequency was 26%, 40%, 50%, or 8% for patients receiving 600, 1200, or 2400 mg/d OXC or placebo, respectively (all p < or = 0.0001). Of patients in the 600, 1200, or 2400 mg/d OXC groups, 27%, 42%, and 50% respectively, had more than 50% reduction in seizure frequency compared with 13% for placebo (all p < 0.001). Higher plasma 10-monohydroxy derivative concentrations were associated with larger decreases in seizure frequency (p = 0.0001). During the double-blind treatment phase, 84%, 90%, 98%, and 76% of patients receiving 600, 1200, or 2400 mg/d OXC or placebo, respectively, reported one or more adverse events. The most common adverse events were related to the nervous and digestive systems.
Conclusions: OXC is safe and effective as adjunctive therapy in patients with uncontrolled partial seizures. OXC 600 mg/d was the minimum effective dosage; effectiveness of OXC increased with dose. The rapid and fixed titration to high doses was associated with an increased risk of adverse events, which could potentially be reduced by adjusting concomitant antiepileptic medication and by using a slower, flexible OXC titration schedule.