FORMULATION AND EVALUATION OF A GASTRO-PROTECTED BILAYER TABLET OF TRAMADOL AND INDOMETHACIN

AbstractThe present study aimed to develop and evaluate a gastro-protected bilayer tablet containingTramadol Hydrochloride and Indomethacin to provide combined analgesic and antiinflammatory therapy through sustained and site-specific drug delivery. TramadolHydrochloride, a highly water-soluble analgesic, was incorporated into a sustained-releaselayer, whereas poorly water-soluble Indomethacin was formulated into a gastro-protectedlayer designed to restrict drug release in acidic gastric conditions and promote release aftertransition to intestinal pH. Preformulation studies confirmed the identity and physicochemicalcharacteristics of both drugs. FTIR analysis indicated retention of characteristic drugfunctional groups without major evidence of chemical incompatibility. UV-visible calibrationcurves demonstrated satisfactory linearity over 2–20 µg/mL for both drugs. Five bilayerformulations (F1–F5) were prepared by varying HPMC K100M and ethyl cellulose in theTramadol layer and sodium starch glycolate in the Indomethacin layer. Pre-compressionparameters indicated acceptable flow and compressibility of the powder blends. The preparedtablets exhibited satisfactory physical characteristics, including adequate hardness, friabilitybelow 1%, uniform weight, and consistent drug content. Tramadol Hydrochloridedemonstrated polymer-dependent sustained release over 12 h, while Indomethacin showedeffective gastro-protection, with only 2.91–3.76% drug release during the initial 2 h in 0.1 NHCl, followed by rapid release in phosphate buffer pH 6.8. Among the formulations, F3exhibited the most desirable dissolution profile, releasing 96.28 ± 1.39% TramadolHydrochloride at 12 h and 99.14 ± 1.06% Indomethacin at 4 h. Overall, F3 was identified asthe optimized formulation, demonstrating the feasibility of bilayer technology for combinedsustained and gastro-protected drug delivery.