Oral Micro-particulate Colon Targeted Drug Delivery System for the Treatment of Crohn's Disease: a Review

Crohn's disease is thought to be an autoimmune disease, in which the body's immune system attacks the gastrointestinal tract, causing inflammation, it is classified as a type of inflammatory bowel disease. The microspheres carrier for the delivery of the dosage form to the colon is composed of physiological and biodegradable natural polysaccharides and which in turn cause low systemic toxicity, low cytotoxicity and lesser side effects. Most of the polysaccharides used in the processing of pharmaceutical formulations have an approved status of generally accepted as safe which includes accepted food additives for human use or as excipients in various dosage forms. Their natural behaviour to release the entrapped drug moiety at neutral or slightly alkaline pH can enhance the absorption of the drug from the colon which has made them popular as a drug carrier to the colon. Furthermore, they provide the possibility to supply the active drug over a prolonged period of time and the microbial flora present in the colon can initiate the drug release from the delivery system containing polysaccharides. The colonic bacteria are predominantly anaerobic in nature and secrete enzymes that are capable of metabolizing both endogenous and exogenous substrates that escape digestion in the upper gastro intestinal tract. The microspheres when formulated into tablets and coated with pH sensitive enteric coated polymers avoid the problem of degradation of the drug by the gastric pH. Thus when the tablet enters into the small intestine the pH sensitive enteric coating does not dissolve completely at the pH of the small intestine (5.5-6.4). However, when the tablets reach the colonic region of the gastro intestinal tract the pH sensitive enteric coating dissolves at the pH of the colon (6.4-7.0) releasing the microspheres compressed tablets at the colon.