Abstract

The main purpose of this research was to study the mechanism of drug release from solid dispersions of albendazole, giving special emphasis to particle size of the drug in solid dispersions. Solid dispersions were prepared using three different carriers, mixing ratios and methods in an attempt to improve the solubility and dissolution rate of albendazole. The mechanism of enhanced dissolution was investigated by a novel dissolution technique as an adjunct to phase solubility study, wettability test, differential scanning calorimetry, X-ray diffractometry, infrared spectroscopy and scanning electron microscopy. The solubility of albendazole was greater with albendazole-poloxamer 407 system, while polyethylene glycol dispersions showed predominant wettability. Physical mixtures showed enhanced dissolution compared with the pure drug, due to improved wetting and solubilization of drug in the diffusion layer offering carrier-rich microenvironment. Preparation of solid dispersion further improved the dissolution compared to the physical mixture, owing to increased surface area for mass transfer, thermodynamically enhanced dissolution of a higher energy amorphous form from the carrier, in addition to improved wetting and solubilization. All carriers showed comparable degree of drug particle size reduction, whereas mixing ratio and method of preparation substantially affected the particle size. Intermolecular association of drug with the carrier led to inhibition of drug recrystallization.