PROCESS FOR THE PREPARATION OF 1,2-DICHLOROETHANE FREE CRYSTALS OF ZONISAMIDE AND THE HIGHLY PURE CRYSTALS OF ZONISAMIDE

摘要

A process for the preparation of crystals of zonisamide containing residual 1,2-dichloroethane of not more than 5 ppm, by adding an aqueous C2-4 alcohol to crystals of zonisamide containing residual 1,2-dichloro-ethane of more than 5 ppm, removing the 1,2-dichloroethane by azeotropic distillation, followed by collecting the precipitated crystals from the residual mixture, and the highly pure crystals of zonisamide containing residual 1,2-dichloroethane of not more than 5 ppm, which is useful as an antiepileptic agent.