Long-term efficacy and safety of zonisamide monotherapy in epilepsy patients

Background and Purpose: Zonisamide (ZNS) is a useful antiepileptic drug with a broad therapeutic spectrum. However, there is limited information on the long-term use of ZNS as a monotherapy. This study investigated the long-term effects of ZNS as a monotherapy for the treatment of epilepsy. Methods: We retrospectively analyzed the records of epilepsy patients treated with ZNS monotherapy at our clinic. We identified outcomes for patients treated with ZNS monotherapy for a minimum of 6 months. Efficacy was quantified as the percentage change in seizure frequency, and safety was assessed by the frequency and types of adverse events. Results: Sixty patients who received ZNS for a minimum of 6 months were included. The mean duration of treatment was 19.8 months (range, 6-37 months), and the mean ZNS dosage was 255 mg/day (range, 100-500 mg/day). Twenty-seven patients (45%) were seizure-free, and an additional 20 patients (33%) had above 50% seizure frequency reduction at the last follow-up visit. Partial seizures with or without secondary generalization and generalized seizures were well controlled by ZNS, whereas complex partial seizures were not. Forty-eight patients (80%) reported mild-to-moderate adverse events, including memory loss (35%), attention deficit (27%), and weight loss (20%). Conclusions: Long-term ZNS monotherapy is effective at treating a broad spectrum of seizure disorders, except complex partial seizures. However, a specific adverse event, such as cognitive impairment, is common and long-lasting.