The human gastrointestinal tract consists of a highly complex ecosystem of aerobic and anaerobic microorganisms that plays a significant role in the metabolism of nutrients as well as drugs. In the colon, bacteria ferment various types of substrates that are not susceptible to digestion in the small intestine. This arouses interest in specific drugs, drug delivery systems, and prodrugs that escape small bowel digestion, arrive intact, and are absorbed or degraded in the large bowel. For the past forty years, experience has been gained with the azo prodrug of 5-amino salicylic acid, salazopyrine, which is cleaved by colonic bacteria to its parent drug. Some laxative drugs were also reported to degrade into active metabolites in the colon. Lately equally interesting and more sophisticated microbial controlled delivery systems, have been developed based on similar principles.
KEY WORDS
Colon Targeting Bacteria Drug release Delivery systems 1. reduced incidence of undesired systemic adverse effects; 2. the ability to cut down on the required dose; 3. supply of drug to the biophase only when it is needed; 4. maintainence of the drug in its intact form as close as possible to the target site.' Since organs such as liver, spleen, bone marrow, and alveoli will normally sequester foreign particles from the bloodstream, it is relatively easy to specifically deliver drugs to the reticuloendothelial system. This is done by techniques such as liposomes, nanoparticles, loaded red blood cells, and recognition factors