Crystal structures and physicochemical properties of amisulpride polymorphs.

The purpose of this work was to investigate the crystal structures and physicochemical properties of amisulpride polymorphs. Except of the previously reported polymorph (named as Form I), a new polymorphic form (named as Form II) was discovered through comprehensive solid-state screening experiments. Both polymorphic forms were characterized by single crystal X-ray structure analysis (SXRD), powder X-ray diffraction (PXRD), dynamic vapor sorption (DVS) and thermal analysis (TGA and DSC) as well. It has been found that the Forms I and II are of conformational polymorph with the main conformational difference around ethylsulfonyl group. Form II possesses lower hygroscopicity and better solubility compared with that of Form I, indicating Form II could be an alternate solid form for formulation development.