Lipid-based vehicles for the oral delivery of poorly water soluble drugs

The use of natural and synthetic lipids has generated much academic and commercial interest as a potential formulation strategy for improving the oral bioavailability of poorly water soluble drugs. Lipid-based formulations can reduce the inherent limitations of slow and incomplete dissolution of poorly water soluble drugs, and facilitate the formation of solubilised phases from which absorption may occur. The attainment of an appropriate pre-absorptive solubilised phase will not necessarily arise directly from the administered lipid, but most likely from the intraluminal processing to which lipids-are subjected. This review attempts to provide a framework for the assessment of lipid based formulations by describing how aspects of GI physiology, and the choice of lipids and their formulation attributes, impact on dose form performance. Lipid digestion is briefly described and the various colloidal phases present within the GI tract during lipid digestion:are highlighted. This is followed by selected examples where lipids have been investigated for improving the absorption of poorly water soluble drugs. Finally, some perspectives are offered such that the design of lipid-based dose forms may become less phenomenological than has been the traditional practice.