Lipids and Surfactants: The Inside Story of Lipid-Based Drug Delivery Systems

In the bioavailability enhancement of poorly aqueous soluble drugs, self-emulsifying/microemulsifying drug delivery systems (SEDDS/SMEDDS) are isotropic mixtures of oils, surfactants, solvents, and cosolvents/surfactants that have gained immense popularity because of their self-emulsification ability. This characteristic relies on some critical parameters such as surfactant concentration, oil-to-surfactant ratio, polarity of the emulsion, droplet size and charge, which are acquired from an amalgamation of appropriate excipients. The fabrication of this combination is of utmost importance for formulation scientists. Hence, to explore the potential of such a delivery system, standardized guidelines for excipients must be developed to address bioavailability issues. In the present review, we summarize the approaches to selecting the most suitable lipid(s)-based drug delivery system, including characterization, especially for oral delivery, of both physicochemical and biopharmaceutical aspects and properties of assorted excipients as well as the related patent reports.