Evaluation of the clearance characteristics of bioadhesive systems in humans

This paper describes the characterisation, radiolabelling and clearance cha racteristics of three bioadhesive nasal delivery systems; starch microspher es, chitosan microspheres and chitosan solution. The time taken for 50% of these bioadhesive materials and a control to be cleared from the nasal cavi ty, after nasal administration to human volunteers, was evaluated using gam ma scintigraphy. The data show that the control was cleared rapidly, with a half life of 21 min, whereas the bioadhesive delivery systems had much lon ger half lives. The clearance of the chitosan solution almost doubled to 41 min, whilst the half life of clearance for the starch microspheres more th an tripled to 68 min and for the chitosan microspheres the half life of cle arance quadrupled to 84 min. From the results reported in this study it is possible to determine that both chitosan systems and the starch microsphere s have good bioadhesive characteristics. The results have supported the hyp othesis that chitosan delivery systems can reduce the rate of clearance fro m the nasal cavity, thereby increasing the contact time of the delivery sys tem with the nasal mucosa, providing the potential for increasing the bioav ailability of drugs incorporated into these systems. (C) 1999 Elsevier Scie nce B.V. All rights reserved.