Structural analysis of polymorphism and solvation in tranilast.

Five polymorphic forms of tranilast were characterized by thermal, diffractometric, and spectroscopic techniques. The crystal structures of the most stable anhydrous form (Form I), a chloroform solvate, and a dichloromethane solvate were determined from single-crystal X-ray analysis. Two additional anhydrous forms of tranilast (Forms II and III) were also studied, but were not amenable to SCXRD.