Long term use of zonisamide in refractory childhood-onset epilepsy

We present data of our open label study of zonisamide as adjunctive treatment in 24 patients (mean age 12.5 years) with different epilepsy syndromes, all refractory to at least 6 antiepileptic drugs (median 10). Mean duration of zonisamide therapy was 55 weeks (5–168); mean maintenance dosage was 7.7mg/kg/day (4–16mg/kg/day). The initial response rate (more than 50% seizure reduction after two month) was 58.3% (=14 patients), 41.7% (=10 patients) have been still on zonisamide treatment after 18 month, with one patient (=4.2%) still seizure free. Zonisamide was overall well tolerated. We observed mild to moderate side effects in 46%. Only in one patient loss of appetite as a side effect led to discontinuation of the treatment. Side effects (decreased appetite, constipation, nausea, behavioural change and seizure aggravation) occurred mostly during titration of the medication and resolved on maintenance dosage.

We conclude – in accordance to former Japanese studies – that long term use of zonisamide as adjunctive therapy may be beneficial for treating refractory childhood onset epilepsy.