Abstract
Zonisamide (ZNS), a new antiepileptic drug which features a wide antiepileptic spectrum, is commonly prescribed concomitantly with other drugs. However, there appears to be little data on the drug interaction of ZNS with other coadministered drugs. Concentrations of ZNS and co-medications in plasma were measured simultaneously by HPLC. The ratio of plasma concentration to the administered dose of ZNS in the monotherapy was significantly higher than that in the polytherapy (P>0.05). When co-medications numbered more than two, the ratio was significantly decreased compared with ZNS alone, indicating the possibility that co-medications induce decreases in plasma concentration of ZNS. The present findings provide useful information that the monitoring of plasma concentration of ZNS is needed to adjust dosage regiments of ZNS in the polytherapy.
