1 World Journal of Pharmaceutical Sciences ISSN (Print): 2321-3310; ISSN (Online): 2321-3086 Published by Atom and Cell Publishers © All Rights Reserved Available online at: http://www.wjpsonline.org/ Editorial Solid dispersions: A feasible technique to improve the aqueous solubility of poorly soluble drugs Dr. D. Nagasamy Venkatesh M. Pharm., Ph.D., Assistant Professor, Department of Pharmaceutics, JSS College of Pharmacy, (A Constituent College of Jagadguru Sri Shivarathreeswara University, Mysuru), Udhagamandalam – 643 001. Tamil Nadu. India. Phone: 00-91-423-2443393 (Ext-216); Fax: 00-91-423-2442937 Mobile: 08903123467, E-mail: nagasamyvenkatesh@rediffmail.com ABSTRACT Solid dispersion technology deals with dispersing one or more active ingredients in an inert matrix in the solid state in order to achieve enhanced dissolution rate and stability. Upon increasing the dissolution rate in the gastro intestinal tract, the rate of absorption is increased as long as the dissolution rate is still the rate-limiting step. Various carriers have been used in the formation of solid dispersion, which can facilitate in improving the dissolution rate of poorly soluble drugs to improve better bioavailability. Key words: Solid dispersion, carriers, dissolution enhancement and applications. INTRODUCTION A drug must possess some aqueous solubility to exert its therapeutic effect 1 . Due to the advancement in chemistry lead to the effective discovery of new drugs. However, 35-40% of these newly discovered drugs suffer from poor aqueous solubility 2-3 . The solubility behavior of a drug is key determinant to its oral bioavailability, and rate- limiting step in absorption of drugs from gastro intestinal tract 4-6 . Poor aqueous solubility of drugs leads to low bioavailability, increase in the dosage and variability in blood concentrations. It is a unique approach to present a poorly soluble drug in an extremely fine state of subdivision in gastrointestinal fluids. This dispersion consists of a microcrystalline dispersion of a poorly soluble drug in a matrix consisting of physiologically inert, readily soluble carrier 7-10 . Exposure of this type of solid dispersion to the gastro intestinal fluids results in dissolution of water soluble carrier and exposes the dispersed poorly soluble drug. The solubility characteristics of the drug may be altered by reduction in particle size. Several insoluble drugs have been shown to improve their dissolution character when incorporated into solid dispersion. It releases the drug through different mechanisms, and the rate of release of drug to the surrounding fluid is mainly dependent on the type of solid dispersion formed 11-13 . Solid dispersion technique has been widely employed to improve the dissolution rate, solubility and oral adsorption of poorly water soluble drug’s 15-16 . The advantages of solid dispersion system includes:  An increase in aqueous solubility of the drug because of its extremely small particle size.  Possible solubilization effect on the drug by the carrier in the surrounding diffusion layer.  Reduction or absence of agglomeration of drug particles.  Excellent wettability and dispersibility of the exposed drug particles in the gastro intestinal fluids.  Formation of metastable polymorphic forms. However, solid dispersion does have certain disadvantages which include change in crystallinity and decrease in dissolution rate on aging. Moisture and temperature have more detoriating effect on these systems and handling is not easy due to tackiness.