Long-term effects of zonisamide in the treatment of epilepsy in children with intellectual disability.

Zonisamide is a new drug with broad-spectrum antiepileptic activity against partial as well as generalized seizures. The purpose of the present study was to compare the long-term efficacy of zonisamide in the treatment of epilepsy in children with intellectual disability (ID) with those with normal intelligence (NI). One hundred and thirty children (74 ID, 56 NI) were included in the study. Fifteen of the subjects were eliminated from the study because of adverse effects or aggravation of seizures. The remaining 115 children (66 ID, 49 NI) were followed up for more than one year. Twenty-eight children (6 ID, 22 NI) were in zonisamide monotherapy. The mean numbers of different antiepileptic drugs were 4.5 and 3 for the ID and NI groups, respectively. The overall improvement rates, defined as a >50% reduction in the number of seizures, were 41% (ID) and 67% (NI) (P<0.01). Side-effects were observed in 27% and 30% of subjects in the ID and NI groups, respectively. However, in the monotherapy group, side-effects were observed in 50% (ID) and in 27% (NI). In conclusion, the effectiveness of zonisamide was weaker in children with ID than those with NI. This is in agreement with the known phenomenon that epileptic children with ID are likely have more intractable seizures than those with NI.