Abstract
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.
Highlights
Oral administration of different dosage forms is the most commonly used method due to greater flexibility in design of dosage form and high patient acceptance
Ulcerative colitis, crohn’s disease and constipation etc., the optimal drug delivery system, is colonic drug delivery system, because it selectively delivers the drug to the colon, but not to the upper GIT6
1.1 Causes of variation of colonic microbe: The bioenvironment inside the human gastrointestinal tract (GIT) is characterized by presence of complex microflora, especially the colon is rich in microorganisms[19], consisting mainly of anaerobic bacteria, e.g. bacteroides, bifidobacteria, eubacteria, clostridia, enterococci, enterobacteria and ruminococcus etc[20]
Summary
Oral administration of different dosage forms is the most commonly used method due to greater flexibility in design of dosage form and high patient acceptance. Among oral dosage forms, increasing interest has currently turned to systems designed to achieve time specific and site specific delivery of drugs[1, 2]. Ulcerative colitis, crohn’s disease and constipation etc., the optimal drug delivery system, is colonic drug delivery system, because it selectively delivers the drug to the colon, but not to the upper GIT6 Large intestine is difficult to reach by peroral delivery, is still deemed to be the ideal site for the delivery of agents to cure the local diseases of the colon[12, 13] by using rectal dosage forms such as suppositories and enemas, which are always not effective since a high variability in the distribution of these forms is observed[14]. A single unit colon targeted drug delivery system may suffer from the disadvantage of unintentional disintegration of the formulation due to manufacturing deficiency or unusual gastric physiology that may lead to drastically compromised systemic drug bioavailability or loss of local therapeutic action in the colon[18]
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