PROCESS FOR THE PREPARATION OF DOXAZOSINE MESYLATE IN A CRYSTAL MODIFICATION DESCRIBED AS FORM A AND AN INTERMEDIATE PRODUCT FOR THE PRODUCTION THEREOF

摘要

A process for preparing doxazosin mesylate in modification A which comprises dissolving doxazosin with methanesulfonic acid in methanol or a mixture of an aprotic, polar organic solvent and methanol, removing any turbidity from the resulting solution, and stirring the resulting clear solution until no further precipitate separates out, removing, washing with methanol, heating the precipitate in the moist state in ethanol and, after cooling, isolating the resulting product is described.