Classification of solid dispersions: correlation to (i) stability and solubility (ii) preparation and characterization techniques

Solid dispersion has been a topic of interest in recent years for its potential in improving oral bioavailability, especially for poorly water soluble drugs where dissolution could be the rate-limiting step of oral absorption. Understanding the physical state of the drug and polymers in solid dispersions is essential as it influences both the stability and solubility of these systems. This review emphasizes on the classification of solid dispersions based on the physical states of drug and polymer. Based on this classification, stability aspects such as crystallization tendency, glass transition temperature (T-g), drug polymer miscibility, molecular mobility, etc. and solubility aspects have been discussed. In addition, preparation and characterization methods for binary solid dispersions based on the classification have also been discussed.