Physical characterization of polymorphic drugs: an integrated characterization strategy

The potential impact of changing crystal forms during late-stage drug development, in terms of cost and product delay, justifies systematic and early characterization of polymorphism. A thorough understanding of polymorph characteristics also allows selection of the best form to market. The authors review the key elements of polymorph characterization (identification and quantitation, structures, properties and structure-property relationships). The emphasis is on recent developments and an integrated characterization strategy for different types of polymorphs using crystallographic, spectroscopic, microscopic and thermal techniques.