Abstract
The surface of a pharmaceutical solid has a direct implication on a wide range interfacial phenomena affecting powder processing, handling, and performance. This chapter employs a first principles approach to unravel the effects of interfaces in solid state pharmaceuticals. The interfaces encountered in pharmaceutical development are addressed first. Then, the fundamental intermolecular forces are presented, along with the thermodynamics of interfacial phenomena. The macroscopic manifestation of these fundamentals in the context of the different interfaces accompanying them with relevant applications from the field of solid dosage forms is then presented. It should be highlighted that the effects of interfacial phenomena should not be examined isolated from the bulk properties of the material and the environmental conditions. The overall properties of the materials have contributions from both bulk and interfacial components. The significance of the contributions from the interfacial component hinges on the surface to volume ratio of the system.