PROCESS FOR THE PREPARATION OF CRYSTALS OF ZONISAMIDE WITHOUT 1,2-DICHLOROETHANE AND CRYSTALS OF VERY PURE ZONISAMIDE.

摘要

A process for the preparation of zonisamide crystals containing residual 1,2-dichloroethane at no more than 5 ppm, comprising the addition of aqueous C2-C4 alcohol to zonisamide crystals containing residual 1,2-dichloroethane in no more of 5 ppm, the removal of said 1,2-dichloroethane by azeotropic distillation to obtain a residual mixture, followed by the collection of precipitated zonisamide crystals containing 5 ppm of 1,2-dichloroethane from the residual mixture at most.