Lipid-based formulations approach emulsions

In this chapter we will provide a brief overview of the early approaches to bioavailability enhancement by use of simple lipid-based delivery systems (lipid solutions, emulsions etc), and then describe recent progress in the application of self-emulsifying- and microemulsion-based formulations. The effects of lipids on the oral bioavailability of co-administered poorly water-soluble drugs may also be classified from a mechanistic (and to a degree, historical) perspective as physicochemically mediated effects (solubility, dissolution, surface area) and biochemically mediated effects (metabolism, transport related events), and these will be approached separately. It is readily apparent, however, that in many cases physicochemically and biochemically mediated mechanisms will operate side by side. In some instances, bioavailability may also be enhanced by the stimulation of intestinal lymphatic transport, and these studies will be addressed in a separate section. 

Clearly, there are several areas associated with lipid-based oral dosage forms in which further knowledge would be desirable. However, there is strong evidence that this deli very approach may afford sign iU cant advantages over more conventional dosage forms. Hence the u.se of emulsions, lipid solvents, and SEDDS IS likely to continue to play an important role in the formulation of poorly soluble drugs in the future. 

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