ABSTRACT
This chapter explains the surfactants and exemplifies their applications in pharmaceutical dosage forms. It describes micelles, types of micelles, critical micelle concentration (CMC), and the factors that affect the size and CMC of micelles. A surfactant preferentially adsorbs to the interface due to its molecular characteristics. Adsorption of surfactant at the interface results in changes in the nature of the interface and reduces interfacial tension between the two liquids. A surfactant molecule has two distinct regions—hydrophilic and hydrophobic. Surfactants are generally classified according to the nature of the hydrophilic group. The hydrophilic regions can be anionic, cationic, or nonionic. Griffin devised an arbitrary scale of values to serve as a measure of relative contributions of the hydrophilic and lipophilic regions of a surfactant to its overall hydrophilic/lipophilic character, which could be used to select emulsifying agents for a given application. This system is now widely known as the hydrophile–lipophile balance (HLB) system.
