Polymorphism of Dehydro-Aripiprazole, the Active Metabolite of the Antipsychotic Drug Aripiprazole (Abilify)

Abstract

Crystal form exploration of dehydro-aripiprazole (dAPZ), the active metabolite of the antipsychotic drug aripiprazole (APZ), elucidated five polymorphs (I, II, III, IV, and V), two methanol solvates, and a monohydrate. The forms were characterized by thermal microscopy, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), single and powder X-ray diffraction (SCXRD and PXRD), and infrared spectroscopy. DSC analysis showed monotropic relationships among polymorphs I, II, III, and IV and enantiotropic relationships for the two form pairs I ↔ V and II ↔ V. Solvent-mediated conversion experiments indicated that Form V is the thermodynamically stable form in the temperature range 5–60 °C and Form I is the stable form at ≥70 °C, where a transition temperature lies between 60 and 70 °C. Two polymorphs of the methanol solvate (SMeOH1 and SMeOH2) were crystallized from methanol solutions in 1:1 dAPZ/methanol molar ratio. SMeOH2 is the thermodynamically stable form of the two methanol solvate...