Bioadhesive microspheres as a potential nasal drug delivery system

The rapid mucociliary clearance mechanism in the nasal cavity can be considered as an important factor when low bioavailabilities are obtained for drugs given intranasally. A nasal delivery system in the form of bioadhesive microspheres has been developed. Studies in human volunteers using gamma scintigraphy showed great differences in clearance times between 3 microsphere systems and two controls. The half life of clearance for starch microspheres was found to be in the order of 240 min as compared to 15 min for the liquid and powder control formulations. The microspheres form a gel-like layer in contact with the nasal mucosa that is cleared slowly from the nasal cavity. In vitro studies using model compounds (cromoglycate and Rose bengal) showed high degrees of loading capacities for the various microsphere systems. Using various physical and chemical approaches, it was possible to a certain degree to control the release of the compounds from the microsphere systems.