Polymorphic study of donepezil hydrobromide

Abstract

Six polymorphs of donepezil hydrobromide <b>1</b>, having unique physical properties have been identified and characterized by various thermal, spectroscopic and powder X-Ray diffraction techniques. During our extensive research on screening the pharmaceutically acceptable salts and polymorphic forms of donepezil, we encountered various polymorphic changes in hydrobromide salt of donepezil in different solvents, temperature, and time conditions. The systematic study led us to prepare six polymorphs and these are characterized by using different analytical techniques such as, powder X-Ray diffraction (PXRD), Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), IR spectroscopy and Karl Fischer techniques. Different methods for the synthesis of each polymorph and characterization of these novel polymorphs have been discussed.