Colon specific drug delivery systems-different systems and approaches: A review

Colon-specific drug delivery systems (CDDS) are desirable for the treatment of a range of local diseases such as ulcerative colitis, Crohn's disease, irritable bowel syndrome, chronic pancreatitis, and colonic cancer. Conventional treatment of these diseases is comprised of drug (chemotherapeutic agents) administration by parenteral route which leading to numerous undesirable effects. Drug targeting is delivery of drug to receptor, organ or to any other specific part of body exclusively. The targeted delivery to the colon can be a potential site for the systemic absorption of several drugs to treat non-colonic conditions and an increase in the availability of drugs at the targeted region and there by reducing the amount of drug required for same therapeutic effect, thus reducing the incidents of adverse effects. Drugs such as proteins and peptides that are known to degrade in the extreme gastric pH, if delivered to the colon intact, can be systemically absorbed by colonic mucosa. Several formulation approaches have been explored in the development colon-targeted drug delivery systems. These approaches involve the use of formulation components that interact with one or more aspects of gastrointestinal (GI) physiology, such as the difference in the pH along the GI tract, the presence of colonic microflora, and enzymes, to achieve colon targeting. New systems and technologies have also been developed for colon targeting and to overcome pervious method's limitations. Colon targeting holds a great potential and still need more innovative work. This article highlights the factors influencing colon-specific drug delivery and colonic bioavailability and provides a systematic discussion of various conventional, as well as updated research on different approaches for formulation and evaluation currently being utilized for the development of CDDS.