Objective: The objective of the present study was to formulate and evaluate the floating in-situ gelling system of diltiazem hydrochloride.Methods: Sodium alginate based diltiazem hydrochloride floating in situ gelling systems were prepared by dissolving hydroxyl propyl methyl cellulose (HPMC) in 25% of water, to which calcium carbonate and diltiazem hydrochloride were added with stirring to form, a proper and a homogenous dispersion of diltiazem hydrochloride. Meanwhile, 30% of water was heated to 60 ˚C on a hot plate to dissolve sodium alginate and cooled to 40 ˚C. The resulting solution was added to HPMC solution and mixed well. To 5% of water at 60 ˚C, sodium methyl paraben was added and dissolved and cooled to 40 ˚C and was added to the above mixture and mixed well. The volume was adjusted finally to 100% with distilled water. Prepared formulae were evaluated for physicochemical properties, drug content, pH, in vitro gelling capacity, in vitro buoyancy, viscosity, water uptake and in vitro drug release.Results: Formulation variables such as type and concentration of viscosity enhancing polymer (sodium alginate) and HPMC affected the formulation viscosity, gelling properties, floating behavior, and in vitro drug release. Formulation F5 and F6 showed the floating time of 5 min and more than 20 h respectively. A significant decrease in the rate and extent of the drug release was observed with the increase in polymer concentration in in-situ gelling preparation. Formulation F4, F5, F6 were shown to have extended drug release until the end of 7 h.Conclusion: The prepared in situ gelling formulations of diltiazem hydrochloride could float in the gastric conditions and released the drug in a sustained manner. The present formulation was non-irritant, easy to administer along with good retention properties, better patient compliant and with greater efficacy of the drug.

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