International Journal of Natural Product Science 2012: Spl Issue 1:194.
Currently only 8% of new drug candidates have both high solubility and permeability. More than 60% of potential drug products suffer from poor water solubility. This frequently results in potentially important products not reaching the market or not achieving their full potential. Improving oral bioavailability of drugs those given as solid dosage forms remains a challenge for the formulation scientists due to solubility problems. Most of the newly invented chemical entities are poorly water soluble. Dissolution is the rate limiting step in case of poorly soluble drugs in process of drug absorption. Poorly soluble drugs are presented with problems of variable bioavailability. Many techniques have been exercised to improve oral bioavailability of drugs. Among several methods, solid dispersion has attracted attention of the researchers for previous 50 years. Solid dispersions improve solubility of drug particles thus enhancing dissolution characteristics of drugs they increase the oral bioavailability. This review will focus on different aspects of solid dispersion preparation; their advantages, major challenges and preparation methods. Various solubility enhancers like water soluble carriers, cosolvents, surfactants and super disintegrant have been examined to aid in solubility enhancement. These significantly help to improve the bioavailability.