Dialyzability of the antiepileptic drug zonisamide in patients undergoing hemodialysis

Abstract

Purpose: The influence of hemodialysis on plasma zonisamide (ZNS) concentration has not been clarified. In this study, the dialyzability of ZNS during hemodialysis was investigated in four ZNS-treated women with systemic lupus erythematosus complicated by seizures. Methods: The total and unbound plasma concentrations of ZNS were measured before and after hemodialysis. The concentration of ZNS in the spent dialysate also was determined. Results: The reduction in plasma ZNS concentration after a 4.5-h hemodialysis was 52.0 ± 7.6%, and the dialyzer (BLF-16GW) clearance of ZNS was 55.1 ± 7.0 ml/min. Dosage was gradually increased up to 200 to 500 mg/day, and the seizures were controlled satisfactorily. Conclusions: The plasma concentration of ZNS was reduced by approximately 50% during one session of dialysis. For patients undergoing daytime hemodialysis sessions every 2 or 3 days, the usual dosage of ZNS (4-8 mg/kg/day) may be prescribed once a day in the evening. If seizures occur after hemodialysis, a supplemental daily dose may be prescribed in the morning.