RESEARCH ARTICLE Asian Journal of Biomedical and Pharmaceutical Sciences 1 (4) 2011, 24-31 * Corresponding author: Khayyam Shaikh | Email: ramzanshek0587@gmail.com Page24 Page24 Page24 Page24 ISSN 2249-622X Page24 Dissolution and Stability Enhancement of Poorly Water Soluble Drug – Lovastatin by Preparing Solid Dispersions Khayyam Shaikh* 1 , Shailesh Patwekar 2 , Santosh Payghan 1 , John D’Souza 1 1 Department of Pharmaceutics, Tatyasaheb Kore College of Pharmacy, Warananagar, Kolhapur, Maharashtra, India 416113. 2 Department of Pharmacy, Swami Ramananad Teerth Marathwada University, Nanded, Maharashtra, India 431606. . ABSTRACT Solid Dispersions greatly enhance the surface area and hence the dissolution rate and the bioavailability of poorly water-soluble drugs are raised. Thus solid dispersions of Lovastatin have been formulated to improve its solubility and dissolution characteristics, reduce dosing frequency and to improve its stability. METHODS: Lovastatin solid dispersions were prepared by solvent evaporation method. The prepared solid dispersions were characterized by Fourier transform infrared (FT-IR) spectroscopy and evaluated for various parameters like drug content, solubility and dissolution studies and different physical properties. RESULTS: FTIR of the solid dispersion showed that the peaks of Lovastatin and polymers were distinguishable and hence there was no chemical interaction between drug and polymer after formation of solid dispersions. The data indicated that solubility increased in all cases. Dissolution data of all solid dispersions also indicated increase in dissolution as compared to pure drug and increase was due to wetting phenomenon of superdisintegrants used for preparation of solid dispersions. CONCLUSIONS: The solvent evaporation method was found to be a promising method for formulating uniform and stable lovastatin solid dispersions with enhanced surface area and dissolution rate. The bioavailability also increased due to increased wettability of the solid dispersions. INTRODUCTION Greater understanding of dissolution and absorption behavior of drugs with low aqueous solubility is required to successfully formulate them into bioavailable drug products. Although salt formation, particle size reduction etc. have commonly been used to increase the dissolution rate of drug, there are practical limitations with these techniques. Therefore formulation approaches are being explored to enhance bioavailability of poorly water- soluble drugs. One such approach that shows significantly enhanced absorption of such drugs is to formulate solid dispersion 1 . Such formulations greatly enhance the surface area and hence the dissolution rate and the bioavailability of poorly water-soluble drugs are raised. DISPERSION OF DRUG WITHIN AN INERT CARRIER IN SOLID STATE IS SOLID DISPERSION SYSTEM: 2 SOLID DISPERSION TECHNOLOGY: Solid dispersion technology can be used to improve the in- vitro and in- vivo dissolution properties of slightly water soluble drugs and to control their dissolution rate 3 . Solid dispersion is a product formed by converting a fluid drug carrier combination into solid state 4 . The mechanism suggested for enhanced solubility and rapid dissolution of dispersion is when the dispersion is exposed to water, the soluble carrier dissolves rapidly leaving the insoluble drug in a state of microcrystalline dispersion of very fine particles. For conventional capsules and tablets, the dissolution rate is limited by size of primary particles formed after the disintegration of dosage form. In this case an average particle size of 5µm is usually the lower limit, although higher particle size is preferred for ease of handling, formulation and manufacturing. On the other hand if a solid dispersion is used, a portion of drug dissolves immediately to saturate the gastrointestinal fluid and excess drug precipitates out as colloidal particles or oily globules of submicron size. Because of such early promises in bioavailability enhancement of poorly water soluble drugs, solid dispersion has become one of the most active areas of research in pharmaceutical field 3,5,6 . METHODS OF PREPARATION OF SOLID DISPERSION: 7, 8 A) MELTING (FUSION) METHOD: In this method physical mixture of drug and carrier is heated directly until it melts. The molten mixture is then cooled and solidified rapidly in an ice bath. The resulting solid mass is then crushed, pulverized and sieved. The basic reason for increase in solubility is that as the melt is rapidly quenched there is super saturation of the drug where the drug molecules are arrested in solvent matrix by instantaneous solidification, usually rapid solidification is achieved by cooling on stainless-steel plates as it favors rapid heat loss. B) SOLVENT METHOD: