COLON TARGETING APPROACHES: PAST, PRESENT AND FUTURE

The colon specific drug delivery system is gaining importance not only for local drug delivery of drugs but also for the systemic delivery of protein & peptide drugs. Colon was considered as black-box as most of the drugs are absorbed from upper part of the GI tract. Colon targeting was aimed mainly because of less enzymatic activity and longer transit time. It also has drawbacks like less water content and presence of fecal content. To achieve successful colon targeted drug delivery, a drug needs to be protected from degradation, release and absorption in the upper portion of the GI tract and then to be ensured controlled release in the proximal colon. The various approaches that can be exploited to target the release of drug to the colon including formulation approaches through pH sensitive system are microbial triggered systems i.e., prodrugs and polysaccharide based system, timed release system, osmotically controlled drug system, pressure dependent release system, programmed pulsatile release system and others.