Zonisamide as add-on treatment for focal epilepsies. An outcome analysis of 74 patients]

Background. Evaluation of efficacy and tolerability of zonisamide (ZNS) used as an add-on treatment in patients with chronic focal epilepsies. Material and Methods. Retrospective data analysis in 74 patients (38 men, 36 women), age 17-61 years (mean 35 years). Duration of epilepsy was 2-50 years (mean 23.3 years). Additional antiepileptic drugs 2- 5 (mean 2.7). Results. The ZNS daily dosage varied between 100 mg and 500 mg (mean 368 mg). Seizure frequency could be estimated in 50 patients; it decreased by at least 50% in 11 patients (22%), remained unchanged in 28 patients (56%), and increased by at least 50% in 11 patients (22%). None of the patients achieved complete seizure control. Side effects were seen in 45/74 patients (60.8%). Adverse events resulting in discontinuation of treatment with ZNS were documented in 24 patients (32.4%). Out of 70 patients, 34 (48.5%) remained on ZNS 12 months after the onset of therapy. Conclusions. In this study, ZNS proved to be an antiepileptic drug with a comparatively low anticonvulsant efficacy as an add-on treatment in patients with chronic focal epilepsies.