A material science perspective of pharmaceutical solids.

This review introduces the basic material science concepts and principles behind some common topics in the development of pharmaceutical solid formulations. The physiochemical properties of small organic pharmaceutical materials are summarized. Common phases, differences in phases, phase transitions, and their relation to pharmaceutical development are reviewed. The characteristics and physical nature of solid phases, including crystalline and amorphous solids, are presented in conjunction with some pharmaceutically relevant phenomena, such as polymorphism, phase transition kinetics, and relaxation. Mesophases, including liquid crystals and condis crystals, are introduced. The potential energy states of different phases are highlighted as the key connection between the physical nature of the materials and their pharmaceutical behavior, and energy landscape is employed to enhance the understanding of this relation.