The challenge of targeting drugs speciﬁcally to the colon has been embraced by scientists over the past two decades. Previously thought of as a Black Box, the colon is recently being explored as an increasingly important site for drug delivery. Research interest in the area of colonic drug delivery has been fuelled by the need to treat debilitating pathologies of the colon like amaebiosis, inflammatory bowel diseases and colon carcinoma, in a better way. Targeted drug delivery to colon would ensure direct treatment at the disease site, lower dosing and reduction in systemic side effects. Colon can also be utilized as a portal for the entry of drugs into the blood for systemic therapy. Drugs that are degraded and/or poorly absorbed in the upper gut may be preferentially absorbed from the colon because of the lower luminal and mucosal digestive enzymes and more residing time, as compared to small intestine. Colonic drug delivery may also be used as a means of achieving chronotherapy of asthma and arthritis that are sensitive to circadian rhythms.
To achieve successful colonic delivery, a drug needs to be protected from absorption and /or the environment of the upper GIT and then be abruptly released into the proximal colon, which is considered the optimum site for delivery of drugs.
Potential candidates for colon-specific delivery are antimicrobials, immunosupressants, aminosalicylates, proteins and peptides. The various strategies for targeting orally administered drugs to the colon include prodrugs, coating with pH-sensitive polymers, timed release systems, exploitation of carriers that undergo colon- specific degradation or plant polysaccharides such as amylose, inulin, pectin and guar gum that remain unaffected by gastrointestinal enzymes, bioadhesive and osmotic controlled drug delivery systems.
My power point presentation deals with challenges, merits, demerits and future trends of colon-specific drug delivery in details.