Abstract
Physical properties of drug molecules play a vital role in the field of pharmaceutics. Since the ultimate goal is to make a dosage form or delivery system safe, effective, and reliable, understanding some of the fundamental concepts in relation to the physicochemical properties of drug molecules is essential. Some of the physical properties that are of great interest to a formulation scientist are ionization, solubility, lipophilicity, hydrogen bonding, molecular size, surface property, and bulk physical properties (crystal shape, particle size, density, and flow). This chapter does not cover all these physical properties; however, some of these properties are described in other chapters. This chapter emphasizes some of the properties related to the surface, flow, and colligative properties, along with some of the common spectroscopic methods used in the analysis of some of these physicochemical properties of drug molecules.