[5] Multiple emulsions as targetable delivery systems

This chapter discusses the multiple emulsions as targetable delivery systems. The stability of a resultant multiple emulsions will depend not only on formulation variables but also on the conditions employed in its production. The objectives will be to produce a multiple emulsion system that has a high yield of multiple droplets, containing the drug entrapped in the innermost phase, and for such a system to have good stability in vitro and the desired release characteristics in vivo. Multiple emulsions of the w/o/w type can be used for drug delivery and drug targeting, particularly as lymphotropic agents. The emulsions can be formulated using mineral or vegetable oils, and can be stabilized by a combination of lipophilic and hydrophilic emulsifiers. Multiple emulsions have generally poor stability characteristics but more stable systems can be created through the use of added complexing and gelling agents.