State of the Art of Pharmaceutical Solid Forms: from Crystal Property Issues to Nanocrystals Formulation

The solid-form screening of active principal ingredients is a challenge for pharmaceutical drug development, as more than 80 % of marketed drugs are formulated in the solid form. A broad and comprehensive study of the various solid forms of drugs is needed to enhance their translation into the clinic. Therefore, the most suitable solid form must be taken into consideration regarding ex vivo and in vivo stability, targeting, solubility, dissolution rate, and bioavailability. In this review, techniques of solid-form screening are covered, including differences in solid forms such as polymorphs, solvates, salts, co-crystals, and amorphous particles. Moreover, solid drug size reduction is also discussed, with insight into the emergence of drug nanocrystal formulations. An overview of the smallest nanocrystals reported in the literature and on the market is also provided, along with their applications and routes of administration.