Long-term safety and efficacy of zonisamide in patients with refractory partial-onset epilepsy.

OBJECTIVES: To investigate whether zonisamide remains effective and well tolerated in the treatment of refractory partial epilepsy during long-term treatment and with flexible dosing in clinical practice.

MATERIALS AND METHODS: Patients with refractory partial epilepsy who completed a fixed-dose, randomized, double-blind clinical trial were recruited in an open-label extension study with adjustment of zonisamide and other antiepileptic drug dosage according to the treating physician's usual clinical practice.

RESULTS: An intention-to-treat analysis of 317 patients showed that zonisamide was well tolerated with a predictable safety profile. Patient retention rates at 1, 2 and 3 years were 65.3%, 44.5% and 28.8%, respectively. Zonisamide treatment was associated with a maintained reduction in seizure frequency, with some patients achieving prolonged periods of seizure freedom.

CONCLUSIONS: Flexible dosing with zonisamide demonstrated a good safety profile and sustained efficacy in the long-term adjunctive treatment of refractory partial epilepsy.