Solid dispersion – a pragmatic method to improve the bioavailability of poorly soluble drugs

Drugs contained in solid oral dosage forms need to have good solubility in order to result in good bioavailability provided they also have good permeability. Recently, controlled release systems utilize solid dispersion technology to achieve an extended release profile of poorly water-soluble drugs with a short biological half-life. There are two main methods for the preparation of solid dispersions: one is through the use of a liquid phase such as melting and solvent methods, and the other is through a solid phase such as mechanical methods. Ball milling has been widely used to make the amorphous phase. Factors which can affect the physical stability of amorphous solid dispersions have been investigated widely, and glass transition temperatures (Tg), molecular mobility, physical stability of amorphous drugs alone, miscibility between drugs and polymers, and solid solubility of drugs in polymers have been considered as key factors influencing the physical stability of solid dispersions.