Short-term efficacy and safety of zonisamide as adjunctive treatment for refractory partial seizures: a multicenter open-label single-arm trial in Korean patients

ObjectiveTo evaluate the efficacy and safety of adjunctive zonisamide (ZNS) therapy in Korean adults with uncontrolled partial epilepsy.MethodsStudy patients had an average of at least one seizure per 4-week (averaged over a 12-week historical baseline) despite the use of one to three antiepileptic drugs. The starting dose of ZNS was 100 mg/day, and was increased to 200 mg/day after 2 weeks. During the 12-week maintenance period, the dose of ZNS was adjusted to 200–400 mg/day based on the physicians’ discretion. The global evaluation scale (GES) and quality of life (QOLIE-31) were also evaluated.ResultsA total of 121 patients were enrolled, of which 88 patients completed the study. The median percent reduction in weekly seizure frequency over the treatment period was 59.0%. The ≥50% and ≥75% responder rates were 57.3% and 38.5%, respectively. Seizure freedom over the treatment period was observed in 25 patients, but seizure freedom throughout the 16-week treatment period was attained in only 16 patients. On investigator's GES, 84 patients were considered improved, with 33 patients showing marked improvement. In QOLIE-31 scale, seizure worry improved significantly but emotional well-being deteriorated. Treatment-emergent adverse events (AEs) were reported in 80 patients. The most common AEs were dizziness (28.1%), somnolence (24.0%), anorexia (18.2%), headache (14.0%), nausea (13.2%), and weight loss (10.7%). Twenty-two patients discontinued the trial due to drug-related AEs.ConclusionsOur results suggest that adjunctive ZNS therapy for the treatment of refractory partial epilepsy, though efficacious, is associated with significant tolerability problems.