Journal of Pharmacy and Alternative Medicine www.iiste.org ISSN 2222-5668 (Paper) ISSN 2222-4807 (Online) Vol 1, 2012 13 Basics of Self Micro Emulsifying Drug Delivery System Barkat Ali Khan* 1 , Satar Bakhsh 1 , Haroon Khan 2 , Tariq Mahmood 3 , Akhtar Rasul 3, 4 1. Department of Pharmaceutics, Faculty of Pharmacy, Gomal University, D.I Khan, Pakistan. 2. Department of Pharmaceutical Chemistry, Gomal University, D.I Khan, Pakistan 3. Department of Pharmacy, The Islamia University of Bahawalpur, 63100, Pakistan 4. School of Pharmacy, Amin Campus, The University of Faisalabad, 37610, Pakistan * E-mail of the corresponding author: barki.gold@gmail.com Abstract About 70-75% of drugs is taken orally and is found not to be as useful as desired. A self-micro emulsifying drug delivery system (SMEDDS) is a drug delivery system that uses a micro-emulsion achieved by chemical rather than mechanical means. Micro-emulsions have significant potential for use in drug delivery, and SMEDDS are the best of these systems. SMEDDS are of particular value in increasing the absorption of lipophilic drugs taken orally. SMEDDS are mixtures of natural or synthetic oils, solid or liquid surfactants, or alternatively, one or more hydrophilic solvents and co-solvents/surfactants that have a unique ability of forming fine oil-in-water (o/w) micro emulsions upon mild agitation followed by dilution in aqueous media, such as GI fluids. SMEDDS spread readily in the GI tract, and the digestive motility of the stomach and the intestine provide the agitation necessary for self-emulsification. SMEDDS can be encapsulated in hard or soft gelatin capsules or can be converted to solid state (Solid SEDDS/SMEDDS). This review article provides an overview of SMEDDS and its advantages over conventional dosage forms. Keywords: SMEDDS, Micro-emulsions, Co-solvents 1. Introduction In recent years, much attention has been focused on oral dosage forms using a self-micro emulsifying drug delivery system (SMEDDS) for the purpose of improving the solubility and absorption of poorly water-soluble drugs. SMEDDS consists of a mixture of drugs, oils, surfactants and/or other additives. Gentle mixing of these ingredients in aqueous media generates micro-emulsions with a droplet size in a range of 10-100 nm. SMEDDS has been shown to improve absorption of drugs by rapid self-micro emulsification in the stomach, with the micro-emulsion droplets subsequently dispersing in the gastrointestinal tract to reach sites of absorption [4]. The resultant small droplet size from SMEDDS provides a large interfacial surface area for drug release and absorption, and the specific components of SMEDDS promote the intestinal lymphatic transport of drugs [5]. Oral absorption of several drugs has been enhanced by SMEDDS [5-8]. 2. Formulation of SMEDDSS SMEDDS are composed of oil, hydrophilic surfactant, and a co-solvent. The process of self-emulsification is only specific to certain combinations of pharmaceutical excipients. It depends on the type of oil and surfactant pair, their ratios, the surfactant concentration and the temperature at which self-emulsification occurs. The primary step during formulation of a S(M)EDDS is the identification of these specific combinations of excipients and construct a phase diagram which shows various concentrations of excipients that possess self-emulsification. Mutual miscibility of these excipients is also important for producing a stable liquid formulation. Long chain triglycerides (LCT) are usually immiscible with hydrophilic surfactants and co-solvents. Polar oils such as mixed glycerides show an affinity towards hydrophilic surfactants and thus are miscible with the surfactant and also aids in self-dispersion of the formulation. The