Zonisamide for refractory juvenile absence epilepsy

To examine the clinical effect of zonisamide (ZNS) in patients with drug-resistant juvenile absence epilepsy (JAE).

Between 2006 and 2010, 13 JAE patients were successively treated with add-on ZNS. Safety and efficacy were assessed according to the patient and caregiver reports at visits every 3 months. Response rate was defined as a 50% or greater reduction in seizure frequency.

Mean age was 42 years. No patient had been seizure free for a period ≥12 months before ZNS. The mean follow-up was 34 months. The mean dosage of ZNS was 388 mg. ZNS was effective for absence seizures (AS) in all patients (more than 50% AS reduction). Four patients reached seizure reduction on 550-600 mg/day. Three (23%) had a reduction in AS frequency >75% and five (38.5%) between 50% and 75%. Seizure freedom was achieved in five patients (38.5%) (three patients with AS only and two with AS plus generalized tonic-clonic seizures (GTCS)). Before ZNS, four patients had AS evolving to absence status. After ZNS, three of them were in the seizure-free group, the later never experienced this type of complication. Among seven patients with AS plus GTCS, two of them did not report any improvement in the frequency of GTCS (29%).

This observational post-marketing study confirms the broad-spectrum activity of ZNS that includes GTCS, myoclonic seizures and now AS. This study provides evidence that add-on ZNS is efficient and well tolerated in adult patients with refractory JAE, even at high doses.