The safety and long-term efficacy of zonisamide as adjunctive therapy for focal epilepsy

Epilepsy is a chronic disease which affects 1% of the population worldwide. As treatment is required for many years or decades, the long-term efficacy and tolerability of antiepileptic drugs are particularly important. Zonisamide (ZNS) is a second-generation antiepileptic drug with a unique structure and multiple mechanisms of action. Here, recently published long-term outcomes of patient cohorts with focal epilepsy undergoing ZNS treatment are discussed. Whereas ZNS monotherapy maintains similar seizure control efficacy to carbamazepine after 2 years of treatment, seizure-free rates are low in pharmacoresistant patients undergoing late adjunctive therapy. In preselected patient populations derived from double-blind studies, long-term seizure reduction and responder rates support sustained ZNS efficacy, good adherence and long-term retention. Adverse effects include somnolence and weight decrease, but data suggest that long-term treatment with ZNS is safe with only rare newly occurring adverse effects, and good long-term tolerability also regarding mood, behavior, cognition and bone maturation.