A Long-term Follow-up of Zonisamide Monotherapy

Summary: Objectives: Several studies have reported the safety and efficacy of zonisamide monotherapy, but studies on its long-term outcomes are limited. This chart review was conducted to evaluate the long-term outcomes of zonisamide monotherapy.

Methods: The charts were reviewed for 77 patients treated with zonisamide as monotherapy for 6–180 months between May 1985 and December 2003. Outcomes were analyzed by the following subcategories: patients with newly diagnosed epilepsy or with antiepileptic drug–resistant epilepsy, the type of epilepsy, patient age, and treatment period.

Results: Of a total of 77 patients, 49 patients (64%) attained 50% or more reduction of seizure frequency and of those patients 38 (49%) attained 75% or more reduction, with 18 patients (24%) becoming seizure-free from 6 to 180 (median 80.6 ± 43.6) months of follow-up. Thirty-eight patients (49%) continued zonisamide monotherapy as of December 2003. Proportions of patients having 75% or more reduction in seizure frequency in subcategories were as follows; 56% in patients with newly diagnosed epilepsy and 48% in patients whose treatment was switched to zonisamide monotherapy owing to lack of efficacy of or adverse reaction to previous antiepileptic drugs; 60% in patients with localization-related epilepsies and 38% in patients with generalized epilepsies; and 49% in pediatric patients and 50% in adult patients.

Conclusion: Long-term zonisamide monotherapy was efficacious in a wide range of patients with epilepsy. Zonisamide did not seem to exhibit a reduction in efficacy during long-term use of up to 180 months.