SOLID DISPERSION AS A STRATEGY FOR SOLUBILITY ENHANCEMENT OF BCS CLASS II DRUGS: RECENT ADVANCES AND EVALUATION TECHNIQUES

Poor aqueous solubility is a major limitation in the development of oral drug formulations, particularly for Biopharmaceutical Classification System (BCS) Class II drugs, where dissolution is the rate-limiting step in absorption. A significant proportion of newly developed drug molecules fall into this category, resulting in low and variable bioavailability. Solid dispersion technology has emerged as an effective strategy to enhance solubility and dissolution rate without altering the chemical structure of the drug. In solid dispersions, poorly soluble drugs are dispersed within hydrophilic polymer matrices, leading to improved wettability, reduced particle size, molecular-level distribution, and conversion from crystalline to amorphous form. Polymers such as polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), hydroxypropyl methylcellulose (HPMC), and Soluplus® are widely used to stabilize amorphous systems and maintain supersaturation. Various preparation techniques including fusion method, solvent evaporation, hot-melt extrusion, and spray drying have been optimized for enhanced performance and scalability. This review highlights the mechanisms, carrier systems, preparation methods, evaluation techniques, and future prospects of solid dispersion systems for improving bioavailability of BCS Class II drugs.