Pharmaceutical solid form screening and selection

Solid form screening is an essential step in drug discovery and development because different solid forms of a drug substance may significantly affect the stability, dissolution, and/or manufacturing of the corresponding drug products. This paper takes up these issues, aiming to provide practical guidance on how to obtain and identify stable solid forms as well as validating proposed crystallization conditions in a set of representative active pharmaceutical ingredients (APIs). Techniques for solid form identification and characterization are discussed from the viewpoint of obtaining forms that are suitable for pharmaceutical development (e.g., physically/chemically stable, easily produced and manipulated on a large scale). Ten representative APIs are taken up for detailed study of their crystallization conditions. The forms are identified definitively using single-crystal X-ray diffraction methods. It is found that for all the APIs in this study, the proposed crystallization methods consistently yield the stable form, as previously identified in the literature.