Colon Targeting Guar Gum Microspheres of 5-Aminosalicylic Acid: Evaluation of Various Process Variables, Characterization and In-vitro Drug Release

Background and objectives: 5-Amino salicylic acid (5-ASA), a drug of choice for the treatment of crohn's disease and ulcerative colitis, rapidly absorbs from the small intestine and there is little localization of 5-ASA in the colon. Thus, we have developed a colon-specific delivery cargo of 5-ASA to release the maximum drug in colon. Methods and Results: 5-ASA loaded guar gum microspheres were prepared by emulsion polymerization technique and optimized for particle size, entrapment efficiency and in-vitro drug release in colonic environment. FTIR, PXRD and DSC were used as the techniques to characterize the drug-polymer interaction. 5-ASA-loaded microspheres offer high entrapment efficiency of 82.39 +/- 1.06% with a mean particle size of 150.32 +/- 11.8 mu m. In-vitro release of optimized formulation indicated 9.32 +/- 0.63 % release of drug in SGF (pH 1.2; without pepsin); 13.93 +/- 0.90 % in SIF (pH 7.5), 32.11 +/- 2.80 % in SCF (pH 7.0; without rat caecal contents) while a significant increase in drug release (94.62 +/- 4.50%) was observed in SCF (pH 7.0) medium containing 4% rat caecal content after 6 days of enzyme induction. Conclusion: 5-ASA loaded guar gum microspheres can be used as therapeutic agent for the treatment of ulcerative colitis.