RESUMO
An important step in oral drug development is to identify drug candidates that show sufficient aqueous solubility and could resist or bypass first-pass metabolism in order to overcome bioavailability problems. Aqueous solubility is characteristically low for Biopharmaceutical Classification System (BCS) class II and class IV drug candidates. Several formulation approaches are being identified to overcome the low solubility aspect of a drug candidate such as particle size manipulation, solid dispersions, inclusion complexes and several of nanoparticle-based options. However, the formulation for drug candidates that in addition to low aqueous solubility shows high intestinal and first-pass metabolism is challenging. The self-emulsifying lipid formulations (SELF) provide a mean for sidestepping these factors and improve the bioavailability of lipophilic and highly first- pass metabolised drugs. Nevertheless, formulation of a successful SELF requires an exhaustive understanding of the component used to formulate them, the behaviour of the formulation within the gastrointestinal (GI) milieu and the mechanism by which the drug is released and absorbed. This review gives a brief description of the formulation aspects of SELF and their potential role to mitigate the bioavailability problem related to lipophilic and highly first- pass metabolised drugs.