Self-dispersing lipid formulations for improving oral absorption of lipophilic drugs

The main purpose of this review is to provide a current and general overview of the existing self-dispersing formulations resulting from dilution into emulsions, microemulsions and surfactant dispersions. The systematic approach used and the presentation of the various physico-chemical and biopharmaceutical aspects should facilitate the comprehension of this interesting field and clarify the main considerations involved in designing and characterizing a specific self-dispersing drug delivery system. Studies have shown that the self-emulsification process is specific to the nature of the oil/surfactant pair, surfactant concentration, oil/surfactant ratio and temperature at which self-emulsification occurs. It was suggested that the ease of emulsification could be associated with the ease by which water penetrates into the various liquid crystalline (LC) or gel phases formed on the surface of the droplet. Numerous bioavailability studies carried out in animals and humans, reviewed in the present study, suggest that hydrophobic drugs are better absorbed when administered in self-dispersing lipid formulations (SDLFs). Examples which illustrate the beneficial use of SDLFs for drug absorption enhancement are presented. This review outlines SDLFs as one of the most promising approaches to overcome the formulation difficulties of these hydrophobic/lipophilic drugs.