NEED OF COLON SPECIFIC DRUG DELIVERY SYSTEM: REVIEW ON PRIMARY AND NOVEL APPROACHES

The colon has gained attention on the delivery of drugs not only for the treatment of local diseases associated with the colon but also for its potential for the delivery of proteins and therapeutic peptides sensitive to the enzymes in both the stomach and small intestine. The proximal or ascendant colon is considered as the optimum site for colon-target delivery of drugs. The successful delivery to the colon requires the exploration of a unique feature of the colonic environment: consideration of tran- sit times in the digestive tract (e.g. formulation of timed release systems, drug with a carrier, bioadhesive system and osmotic con- trolled drug delivery systems), pH (e.g. coating with pH sensitive polymers) and enzymes produced by colonic bacteria (covalent linkage, i.e., exploitation of carriers that are degraded speci?cally by colonic bacteria) (Ashford and Fell, 1994; Basit, 2005; Asghar and Chandran, 2006). It follows that precise colon drug delivery requires that the triggering mechanism in the delivery system only respond to the physiological conditions particular to the colon