Kinetics and Mechanism of Diazepam Release from Solid Dispersions

Abstract

Class II drug diazepam has inadequate dissolution rates limiting absorption. Solid dispersions using polyethylene glycol 2000, polyethylene glycol 4000, and polyvinylpyrrolidone K30 were prepared by solvent evaporation. Phosphate buffer pH 6.8 served as dissolution medium. Polyvinylpyrrolidone K30 showed highest solubility and dissolution improvements. Release kinetics followed Hixson-Crowell cube root law with correlation coefficients 0.9665-0.9977. Low release exponents (<0.45) indicated Fickian diffusion mechanisms.