Abstract
The objective of the study was to evaluate the effect of dissolution media pH on the release of highly water soluble drug diltiazem HCl from sustained release (SR) formulations. For this purpose marketed capsules and prepared hydrophilic matrix tablets of diltiazem HCl SR were utilized. Different kinetic models were applied to drug dissolution data for the determination of release kinetics and mechanisms. Accelerated stability studies were further conducted. Decrease in diltiazem HCl release was observed with increase in the pH of the media. Kinetics of drug release from all formulations was best explained by Baker and Lonsdale model (R-2 = 0.9406 - 0.9951). First order kinetics was also followed by marketed capsules (R-2 = 0.9657 - 0.9964). Release mechanism of all formulations was non-fickian. Similarity factor f(2) was calculated using drug release in water as a reference for each formulation. Accelerated stability studies indicated no significant changes in physico-chemical properties and cumulative percentage drug release.