Devidas G. Bachhav

Novel drug delivery systems are need of recent developments. Controlled drug delivery systems for oral route are widely acceptable and easy to formulate. Oral controlled release systems developed to overcome short comings of conventional controlled released formulations such as short gastric residence time, unpredictable gastric emptying time, unstable at higher pH, site specific absorption, etc. Various approaches have been developed to retain dosage form in stomach for longer period of time. Bioadhesive systems, high density systems, expanding or swelling systems, effervescent buoyant systems has been discovered till date. Drugs those having narrow absorption window in stomach, stable at acidic pH and unstable in the intestinal or colonic pH, having low solubility at higher pH are suitable to develop as buoyant drug delivery systems. Present review focuses on various aspects of buoyant drug delivery systems.

Poor water solubility has always been one of the most fundamental problem in drug delivery. It is estimated that around 40% of drugs in the pipeline cannot be delivered through the preferred route or in some cases, at all owing to poor water solubility. Different methods available to improve solubility and dissolution include salt formation, micronization, chemical modification, pH adjustment, solid dispersion, complexation, hydrotropy, micellar solubilisation. Among these, solid dispersions have proved to be a successful strategy for enhancing aqueous solubility of drugs. The present review focus on different solid dispersion techniques used for the improvement of solubility and dissolution rate of poorly water soluble drugs, carriers used, advantages and limitations of each technique.