Solid dispersion: A comprehensive review on formulation strategies in the pharmaceutical industry

Abstract

Poor aqueous solubility, especially for the drugs in the Biopharmaceutical Classification System (BCS) Class II, highly permeable and low soluble, is one of the primary drawbacks of the oral pharmaceutical formulation development. Solid dispersion (SD) is a technique under consideration to enhance the dissolution and bioavailability of poorly water-soluble drugs. This general outline covers the principles, types, preparation methods, assessment methods, and mechanisms by which solid dispersions improve the solubility and stability. The solid dispersions are characterized by molecular arrangement (eutectic mixtures, solid solutions, glass suspensions, etc.) or the type of carrier (first to fourth generations). The preparation techniques are hot-melt extrusion, spray drying, and solvent evaporation, yet their advantages and disadvantages are stated. The importance of the polymer selection, polymer-drug complexes, and environmental factors on the physical stability of amorphous systems is another important issue, as illustrated in the paper. The review also describes the effect of solid dispersion on increasing bioavailability by increasing wettability, inhibiting recrystallization, decreasing size, and increasing drug supersaturation. Lastly, the methods used in the characterization of SDs and quality control, e.g., FTIR, DSC, PXRD, and SEM, are also discussed in this review. Despite some weaknesses in scalability and stability, solid dispersion is a powerful and versatile approach for enhancing solubility and enabling effective drug delivery.