Evaluation of guar gum as a compression coat for drug targeting to colon

Colon-specific drug delivery systems based on a polysaccharide, guar gum, were evaluated using in vitro and in vivo methods. In vitro drug release studies have shown that guar gum in the form of compression coat applied over indomethacin core tablets protects the drug from being released under conditions mimicking mouth to colon transit. Studies in pH 6.8 phosphate buffered saline (PBS) containing 4% w/v rat caecal contents have demonstrated the susceptibility of guar gum to the colonic bacterial enzyme action with consequent drug release, gamma-scintigraphic studies in human volunteers with technetium-99m-DTPA as a tracer in sodium chloride core tablets compression coated with guar gum have shown that the gum coat protect the drug (tracer in the present study) from being released in the stomach and small intestine. On entering the ascending colon, the tablets commenced to release the tracer indicating the breakdown of the gum coat by the enzymatic action of colonic bacteria. The tablets disintegrated in the ascending colon of all the volunteers, except one, resulting in the distribution of released tracer across the entire colon. The study clearly established that guar gum, in the form of compression coat, is a potential carrier for drug targeting to colon. (C) 1998 Elsevier Science B.V. All rights reserved.