Self-Emulsifying Drug Delivery Systems: Strategy for Improving Oral Delivery of Poorly Soluble Drugs

Drugs are most often administered by the oral route. However, more than 40% of new chemical entities exhibit poor aqueous solubility, resulting in unsatisfactory oral drug delivery. Recently, much attention has been focused on self- emulsifying drug delivery systems (SEDDS) to improve the oral bioavailability of poorly aqueous soluble drugs. SEDDS are isotropic mixtures of oil, surfactants, solvents and co-solvents/surfactants. The principal characteristic of these systems is their ability to form fine oil-in-water (o/w) emulsions or microemulsions upon mild agitation following dilution by an aqueous phase. For lipophilic drugs, which display dissolution rate-limited absorption, SEDDS may be a promising strat- egy to improve the rate and extent of oral absorption. This article gives an overview of the new excipients used in SEDDS and biopharmaceutical aspects of SEDDS. The appli- cation of SEDDS and closely related lipid-based systems as drug delivery vehicles is also introduced, with particular em- phasis being placed on the application of SEDDS in traditional Chinese medicine (TCM).