The aim of present work is to develop colon specific matrix tablets of tramadol using natural almond gum as carrier. Matrix tablets of Tramadol HCl were prepared by using 30, 40, 50, 60 and 70% w/w of tablets of Almond gum as carrier by wet granulation technique. These tablets were compression coated with Eudragit S100 to prevent drug release in stomach. All formulations were evaluated for hardness, friability, weight variation, drug content, in vitro and in-vivo studies. The almond gum was

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... uated by viscosity measurement. Drug-excipient compatibility study was done by using FT-IR &DSC. The coated (FC1 to FC5) and uncoated tablets (F1 to F5) were evaluated for in vitro release of Tramadol HCl after sequential exposure to pH 1.2, pH 7.4 and pH 6.8 respectively for 2hr, 3hr and 19hr in the absence as well as presence of rat caecal content and the corresponding data was fitted to popular release kinetic equations in order to evaluate the release mechanisms-kinetics. The selected formulation was subjected to in vivo targeting efficacy studies by Roentgenography technique. In vivo studies were conducted using rabbits. In vitro release studies indicated that the matrix tablets (F1 to F5) failed to control the drug release in the physiological environment of stomach and small intestine. On the other hand, compression coated formulations were able to protect the tablet cores from premature drug release. Presence of rat caecal content enhances the drug release from the tablets. The release of tramadol from all the formulation followed zero order with non fickian diffusion. X-ray studies confirmed that the tablet successfully reached colon without getting disintegrated in upper G.I.T. The in vivo results confirmed that the drug release was initiated only after a lag time of 5 hrs. The bioavailability of drug was found to be improved (AUC 0-t* 481.82 in case of coated tablets). Based on the results, selective delivery of Tramadol HCl to the colon could be achieved using almond gum as release modifier.