ABSTRACT
The physicochemical principles involved in homogeneous solutions were discussed in Chapter 3. In some instances, drug solubility is so low that a homogeneous mixture of the drug in a pharmaceutical solvent cannot be achieved or the liquid form of the drug is not miscible in pharmaceutical solvents. In addition, pharmaceutical scientists design uniformly distributed multiphase systems to enhance drug stability and absorption. At least two phases are present. The plane that keeps apart the two phases is described as an interface or interfacial surface. Interfacial surfaces show different properties from those of bulk phases. Activities of the molecules in the interfacial surface play an important role in pharmaceutical dosage forms. Interfaces of pharmaceutical interest include liquid/solid, liquid/liquid, and liquid/vapor. The liquid/vapor system was discussed in Chapter 3; the liquid/liquid (emulsion) and liquid/solid (suspension) systems will be discussed in this chapter.
