Chitosan and its derivatives as drug penetration enhancers

The review deals with the penetration enhancement properties of chitosan and its derivatives for oral, nasal, buccal and vaginal drug delivery applications. Penetration enhancement through the ocular epithelium and through the skin are beyond the scope of this paper. Extensive experimental evidence has been given of the absorption enhancement properties of chitosan with regard to hydrophilic molecules of different molecular weights. The mechanisms involved in the enhancement effect of chitosan are different depending on whether the epithelia are endowed with tight junctions (intestinal and nasal) or lack tight junctions (buccal and vaginal). Chitosan and its derivatives, when applied in solution to the mucosal site, are capable of facilitating the paracellular route by opening the tight junctions or by interacting with extra-cellular matrix components. The added value of chitosan nanocarriers in promoting drug absorption is also considered. Nanocarriers are capable of being internalized by cells in different areas, thus promoting drug transport. Moreover their mucoadhesive properties and their ability to protect macromolecular drugs from degradation indirectly contribute to enhancing absorption.