SIMPLE AND SENSITIVE ASSAY OF ZONISAMIDE IN HUMAN SERUM BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY USING A SOLID-PHASE EXTRACTION TECHNIQUE

A rapid and sensitive method for the assay of zonisamide in serum was developed using a solid-phase extraction technique followed by high-pe rformance liquid chromatography. A 20-mu l volume of human serum was f irst purified with a Bond-Elut cartridge column. Then, the methanol el uate was injected onto a reversed-phase HPLC column with a UV detector . The mobile phase was acetonitrile-methanol-distilled water (17:20:63 , v/v) and the detection wavelength was 246 nm. The detection limit wa s 0.1 mu g/ml in serum. The coefficients of variation were 4.2-5.6% an d 5.1-9.1% for the within-day and between-day assays, respectively. Th is method can be used for clinical pharmacokinetic studies of zonisami de in serum even in infant patients with epilepsy.