This study assessed the efficacy and safety of the neuronal potassium channel opener ezogabine (US adopted name; EZG)/retigabine (international nonproprietary name; RTG) as adjunctive therapy for refractory partial-onset seizures.

This was a multicenter, randomized, double-blind, placebo-controlled trial in adults with ≥4 partial-onset seizures per month receiving 1 to 3 antiepileptic drugs. EZG (RTG) or placebo, 3 times daily, was titrated to 600 or 900 mg/d over 4 weeks, and continued during a 12-week maintenance phase. Median percentage seizure reductions from baseline and responder rates (≥50% reduction in baseline seizure frequency) were assessed.

The intention-to-treat population comprised 538 patients (placebo, n = 179; 600 mg, n = 181; 900 mg, n = 178), 471 of whom (placebo, n = 164; 600 mg, n = 158; 900 mg, n = 149) entered the maintenance phase. Median percentage seizure reductions were greater in EZG (RTG)–treated patients (600 mg, 27.9%, p = 0.007; 900 mg, 39.9%, p < 0.001) compared with placebo (15.9%). Responder rates were higher in EZG (RTG)–treated patients (600 mg, 38.6%, p < 0.001; 900 mg, 47.0%, p < 0.001) than with placebo (18.9%). Treatment discontinuations due to adverse events (AEs) were more likely with EZG (RTG) than with placebo (placebo, 8%; 600 mg, 17%, 900 mg, 26%). The most commonly reported (>10%) AEs in the placebo, EZG (RTG) 600 mg/d, and EZG (RTG) 900 mg/d groups were dizziness (7%, 17%, 26%), somnolence (10%, 14%, 26%), headache (15%, 11%, 17%), and fatigue (3%, 15%, 17%).

In this dose-ranging, placebo-controlled trial, adjunctive EZG (RTG) was effective and generally well tolerated in adults with refractory partial-onset seizures.

This study provides Class II evidence that adjunctive EZG/RTG reduces the occurrence of partial-onset seizures.