Crystal forms of atorvastatin.

The objective of this work was to investigate the existence of new polymorphs and pseudopolymorphs of atorvastatin and the transformation of crystal forms. Three crystal forms of atorvastatin have been isolated by recrystallization and characterized by powder X-ray diffractometry (PXRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TG). The PXRD and DSC patterns of the three crystal forms were different respectively and it was confirmed that Form 3 is a new crystal form. After storage of 2 years at room temperature, this new crystal form was not transformed and it was shown to have a good physical stability.