MULTIPARTICULATE COMBINED APPROACHES FOR COLON SPECIFIC DRUG DELIVERY

In order to achieve a successful colon targeted drug delivery system, a drug needs to be protected from degradation, release and/or absorption in the upper portion of the gastrointestinal tract (GIT) and then ensure abrupt or controlled release in the proximal colon. Such a system can be formulated by utilizing microbial triggering degradation of polymer coating/ gastro intestinal (GI) transit time (time dependent)/ pH dependent approach etc. But unfortunately it has been found that colonic microflora, GI transit time and pH varies considerably inside a human system by several factors, in addition to this the native biodegradable polysaccharides which are used widely for the microbial triggering colonic drug delivery system (CDDS), are having high aqueous solubility on account of which a single unit colon targeted drug delivery systems may suffer from dose dumping due to overall catastrophic failure of the film around a monolith, which would then release the whole drug, that may lead to drastically compromised systemic drug bioavailability or loss of local therapeutic action in the colon. This review emphasizes some of the causes which make a single unit dosage form unsuitable for targeting to colon by using microbial triggering/GI transit time/pH dependent approach, and at the same time discusses researches which have been carried out to alleviate these problems by utilizing multiparticulate combined approaches.