ABSTRACT
A pharmaceutical suspension is the dispersion of solid particles in a liquid medium in which the drug is not readily soluble. This chapter describes factors that affect the physical stability of suspensions. It also describes the commonly used approaches for the preparation of stable suspensions. The chapter explains Stokes' law and its application in the stabilization of suspensions. Forces at the surface of the dispersed particles affect the degree of flocculation and agglomeration in a suspension. Controlled flocculation is usually achieved by a combination of particle size control, the use of electrolytes to control zeta potential, and the addition of polymers to enable the formation of weak networks in solution that entangle and form weak bonds between the dispersed particles. Based on the route of administration, suspensions can be classified as oral, topical, ophthalmic, otic, or nasal suspensions. Each of these present unique challenges and requirements in terms of desired quality attributes.
