Colon Cancer and Specific Ways to Deliver Drugs to the Large Intestine

Background: It has been postulated that colon cancer is the third cause of cancer death worldwide. Recently, colon-targeted drug delivery systems have been developed for improving systemic drug delivery and treatment of local colon associated diseases. Using such drug delivery systems increases the drug's effectiveness and results in reduced systemic side effects. Drug delivery systems formulated for the colon requires that the triggering of drug release mechanism is designed based on the colon’s physiological conditions. However, improving the site specificity and drug release kinetics of colon-targeted drug delivery systems is desired and is currently under active research. Objective: This review discusses colon cancer along with various colon-targeted drug delivery systems such as pro-drug formation, pH-sensitive polymers, hydrogels, time-dependent release systems, bio-adhesive and nanoparticle systems. The aim is to understand the effect of using colon-targeted drug delivery systems on therapeutic effectiveness of the drug by improving its degradation and bioavailability. Colon targeting holds a great promise as a therapeutic approach but it still requires more innovation. Conclusion: The distribution of the drugs in the colon suffers from problems related to the pH, retention time, micro-flora, and degrading enzymes of gastrointestinal tract. Moreover, these drug delivery systems are capable of overcoming some of the limitations in common targeting approaches. A precise assessment of such systems needs the use of various assaying protocols in order to characterize their traits and clarify their design rationales.