Zonisamide: A new antiepileptic drug

Zonisamide(ZNS) is a relatively new antiepileptic medication currently avai lable in Japan. Attempts to market the drug in the United States were thwar ted by reports of nephrolithiasis by European and American investigators. H owever, successful marketing of the drug in Japan has resulted in a renewed interest in bringing the drug to the United States. Japanese experience wi th ZNS showed a broad spectrum. of efficacy in the treatment of seizures, i ncluding infantile spasms and myoclonic seizures. A neuroprotective role an d an antimanic effect have also been reported. The exact antiepileptic mech anism of action of ZNS is not known, but it has dose-dependent sodium chann el blocking and T-type calcium channel blocking properties and free radical scavenging actions. Recommended initial adult dosage in Japan is 100-200 m g/d, increased if necessary to 200-400 mg/d, up to a maximum of 600 mg/d. I n children, initial dosage is 2-4 mg/kg/d, increased if necessary to 4-8 mg /kg/d up to a maximum of 12 mg/kg/d. The recommended therapeutic plasma ZNS concentration is 10-20 mg/L. Adverse events, most notably drowsiness, loss of appetite, gastrointestinal problems, and CNS toxicity, have been noted with plasma ZNS concentrations of >30 mg/L. A drug rash also has been repor ted.