Author(s): Srikant Bhaargava
Oral route is the most convenient and preferred route but other routes for CDDS may be used. Rectal administration offers the shortest route for targeting drugs to the colon. However, reaching the proximal part of colon via rectal administration is difficult. Rectal administration can also be uncomfortable for patients and compliance may be less than optimal. Administration of glucocorticoids namely dexamethasone by oral route produce systemic side effects including adenosuppression, immunosuppression, cushinoid symptoms, and bone resorption. Thus selective delivery of drugs to the colon could not only lower the required dose but also reduce the systemic side effects caused by high doses. The aim of the present investigation was to prepare colon targeted microspheres of Dexamethasone using a combination of time and pH dependent polymer that offer protection to the drug until it leaves the stomach which is provided by pH dependent polymethacrylate polymer, Eudragit S 100 and major drug release in small intestine is avoided by providing pH independent coating of Chtosan. For preparation of colon targeted microspheres the Microspheres of dexamethasone were first prepared with pH independent polymer Chitosan then with outer layer of a pH dependent polymer Eudragit L100.