ABSTRACT
This chapter discusses the physicochemical aspects of microparticle formation by processes that involve removal of volatile solvent from a multiphase emulsion. Processes that accomplish this involve a combination of solvent extraction and solvent evaporation. System temperature, pressure, and rate of agitation are three factors that affect morphology and size of microparticles produced by all in-liquid drying processes. Drug structure, initial drug concentration in the dispersed phase, and initial drug and polymer ratio represent factors that determine effectiveness of a specific aqueous-phase emulsifier. A number of drugs differing greatly in water solubility and chemical structure have been incorporated in microparticles by in-liquid drying protocols that utilize an oil-in-water-oil emulsion. Actual drug loadings often are measurably lower than expected due to loss of drug to the aqueous phase. Active agent aqueous-phase solubility is reduced when the aqueous phase is transformed into a concentrated inorganic salt solution.
