The objective of the present investigation is to prepare and evaluate the sustained release matrix tablets of Diltiazem hydrochloride. In this investigation, sustained release matrix tablets of Diltiazem hydrochloride were prepared using a natural polymer, is Gum karaya. Total twelve formulations (DK1-DK12) were prepared by using different proportions of drug and Gum karaya (1:0.5, 1:1, 1:1.5, 1:2) with the aid of granulating fluids such as distilled water, ethanol and isopropyl alcohol. The tablets were evaluated for various quality control parameters like hardness, weight variation, friability and assay. The drug release studies were performed by using USP Dissolution apparatus Type II method, in distilled water. From 12 formulations DK4, DK8 and DK12 were optimized based on results from physicochemical evaluation and drug release studies. These formulations have composition of 1:2 ratio of drug and Gum karaya & they have shown more than 95% drug release at 12 hours. Hence based on studies, DK10 was selected for further studies by employing electrolytes in different concentrations (25mg, 50mg and 75mg). These electrolytes were employed to examine matrix swelling and gel properties. These were tested for release studies and to signify the influence of electrolytes type (Sodium carbonate, Calcium carbonate, Magnesium carbonate) in sustaining the release of drug. Based on results the formulation DKE8 was found to extend the drug release over extended period of time. The results signified that the drug released at a sustained rate, owing to differential swelling rate and matrix rigidity, and provides a uniform gel layer.
