Clinical experience with zonisamide monotherapy and adjunctive therapy in children with epilepsy at a tertiary care referral center

We evaluated our clinical experience with zonisamide, a broad-spectrum antiepileptic drug, in a group of children with predominantly medically refractory epilepsy. A retrospective chart review was conducted on patients at our tertiary referral center following Institutional Review Board approval. Observers documented reports of seizure frequency, and seizure types were identified either clinically or by prior video-electroencephalography monitoring. We identified 68 patients (age range 1.9-18.1 years median 6.9 years]; male to female ratio 1.3:1) treated with zonisamide for 0.7 to 28.9 months; at the last visit, 22% and 78% were on monotherapy and adjunctive therapy, respectively. The median duration of treatment and maintenance dose at the end of the follow-up were 11.2 months and 8.0 mg/kg/day, respectively. Seizure types included generalized (primary generalized tonic-clonic, myoclonic, tonic, atonic, absence) and partial (simple, complex, and secondarily generalized tonic-clonic seizures); 10 (15%) patients had both partial and generalized seizures. Sixteen (25.8%) patients were seizure free, although five of them were already in remission prior to starting zonisamide. Thirteen (21.0%) patients had a > 50% seizure reduction, 10 (16.1%) patients had a < 50% seizure reduction, 14 (22.6%) had no improvement in baseline seizures, and 9 (14.5%) reported having increased seizures. The latter were mostly associated with dosage alterations in concomitant antiepileptic drugs. Common side effects were central nervous system related, including behavioral or psychiatric (23.5%), cognitive dysfunction (12.0%), and sedation (10.3%). Eleven (16.2%) patients ultimately discontinued zonisamide, but only five were strictly due to side effects. Zonisamide is clinically effective against multiple seizure types in a significant proportion of children with epilepsy across a broad age range. Drug discontinuation as a result of side effects is uncommon.