SELF- MICRO EMULSIFYING DRUG DELIVERY SYSTEM: A NOVEL APPROACH FOR ENHANCEMENT OF ORAL BIOAVAILABILITY OF POORLY SOLUABLE DRUGS

  As a consequence of modern drug discovery techniques, there has been a steady increase in the number of new pharmacologically active lipophilic compounds that are poorly water-soluble. Approximately 40% of new drug candidates have poor water solubility and oral delivery of such drugs is frequently associated with implications of low bioavailability, high intra and inter subject variability, lack of dose proportionality and therapeutic failure. It is a great challenge for pharmaceutical scientists to convert those molecules into orally administered formulations with sufficient bioavailability. Among the approaches to improve the oral bioavailability of these molecules, the use of self-emulsified drug delivery systems (SEDDS) has been shown to be reasonably successful in improving the oral bioavailability of poorly water-soluble and lipophilic drugs. SEEDS is ideally an isotropic mixture of oils and surfactants and sometimes co-solvents. Hydrophobic drugs can be dissolved in these systems, enabling them to be administered as a unit dosage form for per-oral administration. When such a system is released in the lumen of the gastrointestinal tract, under conditions of gentle agitation provided by digestive motility of stomach and intestine, it spontaneously disperses to form a fine relatively stable o/w emulsion (micro/nano) with the aid of GI fluid. This leads to in situ solubilisation of drug that can subsequently be absorbed by lymphatic pathways, bypassing the hepatic first-pass effect.