Effect of formulation variables on drug and polymer release from HPMC-based matrix tablets

The objective of this work was to assess the effect of two formulation variables, hydroxypropylmethylcellulose (HPMC)/lactose ratio and HPMC viscosity grade, on the release of a model drug and HPMC, as well as the mechanism of drug release from HPMC-based matrix tablets. A water-soluble compound, adinazolam mesylate, was used as the model drug. Both drug and HPMC release were found to be a function of the formulation variables, with higher drug and HPMC release rates for formulations with lower HPMC/lactose ratios and lower HPMC viscosity grades. However, the K15M and K100M formulations had identical drug release profiles. All the drug release data fit well to the Higuchi expression. By comparing the drug and HPMC release data, it was concluded that diffusion of drug through the hydrated gel layer was the predominant drug release mechanism for most of the formulations studied.