Objectives To evaluate the valproate plasma l ev els,the clinical efficacy and adverse effects in patients with epilepsy treated with the conventional preparations and the sustained-release preparations of sodium valproate (VPA-Na?SR).Methods 33 patients received oral conventional formul ation of sodium valproate for over six months and a similar dosage of VPA-Na?SR for 4 weeks.After 12 or 24 hours,the valproate plasma concentr ations of the two formulations were measured respectively before taking drugs in the early mor ning.The valproate plasma concentrations and the clinical efficacy of the VPA-N a?SR were assessed by comparing with that of conventional valproate.The adverse effects were recorded.Results The average valproate plasma trough concentration was s ignificantly higher in patients receiving VPA-Na?SR than that of those receiving conventional valproate.Seizure free in patients was achi eved by 76%(n=25) with VPA-Na?SR and by 45%(n=15) with conventional valproate resp ectively.There was statistical difference between the two formulations.The seizu re frequency was significantly reduced in 5 patients treated with VPA-Na?SR.A dverse ef fects were observed in 2 patients with conventional valproate,5 patients with V PA-Na?SR whose valproate plasma levels were higher than that of conventional p reparations.Adverse effects were related to increased valproate plasm a levels and individual drugtolerance. Conclusions The advantage of VPA-Na?SR is that serum valproa te con centrations may increase smoothly and minimize fluctuation in serum dr ug concentrations during a dosing interval. It is a more effective and more convenient antiepileptic agent.