Characterization and Evaluation of the Release Kinetics of a Model Poorly Water-Soluble and Low Dose Drug from Matrix Tablets Composed of Blends of Swellable and Erodible Polymers: Implications for Controlled and Complete Release

The specific aim of this study was to prepare sustained release matrix tablets containing indapamide as a low dose and low water solubility model drug. The matrix formers were composed of blends of hydroxypropyl methylcellulose as a swellable polymer and methyl cellulose as an erodible polymer. The matrix tablets were prepared by the direct compression technique and they have shown robust and acceptable physical properties with a content uniformity within the acceptable limits. Lactose and microcrystalline cellulose were investigated as additives to these matrices in order to adjust and modulate the release of the drug from the matrices to achieve a release profile similar to that obtained from the reference commercial product, Natrilix. All matrix tablets prepared with these two additives have gave a release profile that is close to zero order kinetics, however, the matrix tablets prepared with lactose gave a release profile with closer resemblance to that of the reference product with a similarity factor (F2) of 86. This is attributed to the rapid water solubility of lactose which enhanced higher erosion of the tablets, and thus, higher dissolution and diffusion of the drug. Microcrystalline cellulose is a swellable polymer where it has resulted in delayed release of the drug with time as compared to the reference product. Investigation of the mechanism of release of the drug from the matrices indicated that erosion is the dominant mechanism of drug release from these matrices.