Studies of guar gum compression-coated 5-aminosalicylic acid tablets for colon-specific drug delivery.

The aim of this study was to develop colon-specific delivery systems for 5-aminosalicylic acid (5-ASA) using guar gum as a carrier. Core tablets containing 5-ASA were prepared by wet granulation with starch paste and were compression coated with coating formulations containing different quantities of guar gum (300, 200, 150, and 125 mg). In vitro drug release studies were carried out in simulated gastric and intestinal fluids and in pH 6.8 buffer containing rat cecal contents. The application of 175 mg of coating formulation containing 150 mg of guar gum over 5-ASA core tablets resulted in the release of less than 2% drug in simulated gastric and intestinal fluids and about 93% of 5-ASA in pH 6.8 buffer containing rat cecal contents. Differential scanning calorimetric (DSC) studies showed the absence of any interaction between 5-ASA and the excipients on storage at 45 degrees C for 12 weeks. The study confirmed that selective delivery of 5-ASA to the colon can be achieved using guar gum as a carrier in the form of a compression coating over the drug core.