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.
Keywords: BCS, lipidic excipients, lymphatic absorption, precipitation, SELF, supersaturation.
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