Abstracts

RATIONALE: Zonisamide (Zonegran[reg]) is a broad-spectrum antiepilepsy drug (AED) that has been available in Japan since 1989 and was approved in the United States in March of 2000 for the adjunctive treatment of partial seizures in adults. The objective of this study was to evaluate the efficacy and safety of zonisamide in children with atonic and/or myoclonic seizures.
METHODS: This retrospective chart review evaluated 11 pediatric patients with atonic and/or myoclonic seizures receiving zonisamide. Efficacy of zonisamide was assessed via reduction in the frequency of atonic and myoclonic seizures. Safety was evaluated via reports of adverse events.
RESULTS: Mean patient age was 5.5 years (range=2 to 13 years). Mean age at seizure onset was 1.0 year (range=birth to 4 years). Six patients (54.5%) had myoclonic seizures, 4 patients (36.4%) had atonic seizures, and 1 patient (9.1%) experienced both atonic and myoclonic seizures. Eight patients (72.7%) had other seizure types in addition to atonic/myoclonic seizures. All patients had been previously treated with at least 3 AEDs, and the number of current AEDs (in addition to zonisamide) ranged from 1 to 2. Mean zonisamide dosage was 372.7 mg/d (range=200 to 600 mg/d) or 21.5 mg/kg per day (range=12.5 to 35 mg/kg per day). Of those with myoclonic seizures, 1 patient was seizure free for a period of 10 months after having experienced daily seizures refractory to trials of at least 5 other AEDs, 2 patients had [gt]50% improvement, and 3 patients had no change in seizure frequency after receiving zonisamide. Of those with atonic seizures, 1 patient was seizure free for a period of 5 months. This patient with Lennox-Gastaut syndrome had previously experienced daily seizures and had failed trials of at least 6 AEDs. Two patients had slight improvement, and 1 patient had no change in seizure frequency after receiving zonisamide. The patient with both myoclonic and atonic seizures had [gt]50% improvement in seizure control while on zonisamide. Four patients experienced adverse events, which included drowsiness (n=1), vomiting/diarrhea (n=1), decreased appetite (n=1), and increased phenytoin levels (n=1) in a patient who was concurrently receiving phenytoin.
CONCLUSIONS: The majority of patients in this chart review experienced slight improvement or better seizure control while on zonisamide. Zonisamide was also safe and well tolerated in this group of pediatric patients. Further studies are warranted to investigate the use of zonisamide for treating myoclonic and atonic seizures in pediatric patients.