ABSTRACT
A dispersion can be defined as a heterogeneous system in which one phase is dispersed (with some degree of uniformity) in a second phase. The state of the dispersed phase (gas, solid, or liquid) in the dispersion medium defines the system as a foam, suspension, or emulsion. Of the various pharmaceutical dosage forms, liquid disperse systems are the most complex. Method of manufacture, formulation approach, component materials selection, and the effect of environmental factors, such as temperature and holding-time, profoundly affect the variability in the product’s bioavailability, stability characteristics, and a host of other variables. Drug molecules can either be encapsulated in the aqueous space, or intercalated into the lipid bilayer; the exact location of a drug in the liposome depends on its physicochemical characteristics and the composition of the lipids. A knowledge of the surface properties of the system also helps in identifying the various available options and the most successful strategies for preparing the best formulation.
