Spray-Drying, Solvent-Casting and Freeze-Drying Techniques: a Comparative Study on their Suitability for the Enhancement of Drug Dissolution Rates

Abstract

Purpose Solid dispersions (SDs) represent the most common formulation technique used to increase the dissolution rate of a drug. In this work, the three most common methods used to prepare SDs, namely spray-drying, solvent-casting and freezedrying, have been compared in order to investigate their effect on increasing drug dissolution rate. Methods Three formulation strategies were used to prepare a polymer mixture of polyvinyl-alcohol (PVA) and maltodextrin (MDX) as SDs loaded with the following three model drugs, all of which possess a poor solubility: Olanzapine, Dexamethasone, and Triamcinolone acetonide. The SDs obtained were analysed and compared in terms of drug particle size, drug-loading capacity, surface homogeneity, and dissolution profile enhancement. Physical-chemical characterisation was conducted on pure drugs, as well as the formulations made, by way of thermal analysis and infrared spectroscopy. Result The polymers used were able to increase drug saturation solubility. The formulation strategies affected the drug particle size, with the solvent-casting method resulting inmore homogenous particle size and distribution when compared to the other methods. The greatest enhancement in the drug dissolution rate was seen for all the samples prepared using the solvent-casting method. Conclusion All of the methods used were able to increase the dissolution rate of the pure drugs alone, however, the solventcasting method produced SDs with a higher surface homogeneity, drug incorporation capability, and faster dissolution profile than the other techniques.