Design and Evaluation of Submicron Emulsions as Colloidal Drug Carriers for Intravenous Administration

Emulsions are heterogeneous systems in which one immiscible liquid is dispersed as droplets in another liquid. Lipid emulsions were developed after World War II to serve as an intravenous source of both calories and essential fatty acids. Since emulsions are thermodynamically unstable systems, a mixture of surfactants should be added for better stability. Most of the known synthetic and efficient emulsifiers are toxic upon parenteral administration due to hemolysis. Submicron emulsions intended for parenteral administration are designed for the incorporation of lipophilic and hydrophobic drugs, which exhibits poor aqueous solubility. Numerous investigators have pointed out various reasons explaining the drastic decrease in the release rate of a drug from the emulsions using the dialysis technique. Intravenously administered emulsions are excellent carriers for lipophilic drugs which are often difficult to delivery; they are biodegradable, biocompatible, physically stable and relatively easy to produce on large scale.