Zonisamide for the treatment of myoclonic seizures in progressive myoclonic epilepsy: an open-label study.

PURPOSE To examine the safety and efficacy of zonisamide in treating myoclonic seizures associated with progressive myoclonic epilepsy (PME), in an open-label setting. METHODS Thirty patients with refractory PME (aged > or = 5 years), who were taking up to three antiepileptic drugs, received adjunctive zonisamide (< or = 6 mg/kg/day) therapy for 16 weeks. Myoclonic seizures were recorded daily over a 24-hour period or in 10-minute epochs in the morning, afternoon, and evening. Safety was assessed via adverse events (AEs); efficacy was measured by the percentage of patients experiencing a > or = 50% decrease in myoclonic seizure frequency from baseline. RESULTS Treatment-related AEs, experienced by 53% (n = 16/30) of patients, led to five patients discontinuing zonisamide. The most common AEs were decreased appetite, somnolence, and asthenia. Overall, 36% of patients (n = 10/28) had a > or = 50% reduction in myoclonic seizure frequency. CONCLUSIONS These results suggest that zonisamide may be useful in the treatment of patients with PME. However, due to the size and open-label character of this study, further research is required.