ABSTRACT
New enrofloxacin microspheres were formulated, and their physical properties, lung-targeting ability, and tissue distribution in rats were examined. The microspheres had a regular and round shape. The mean diameter was 10.06 microm, and the diameter of 89.93% of all microspheres ranged from 7.0 microm to 30.0 microm. Tissue distribution of the microspheres was evaluated along with a conventional enrofloxacin preparation after a single intravenous injection (7.5 mg of enrofloxacin/kg bw). The results showed that the elimination half-life (t(1/2beta)) of enrofloxacin from lung was prolonged from 7.94 h for the conventional enrofloxacin to 13.28 h for the microspheres. Area under the lung concentration versus time curve from 0 h to infinity (AUC(0-infinity)) was increased from 11.66 h.microg/g to 508.00 h.microg/g. The peak concentration (Cmax) in lung was increased from 5.95 microg/g to 93.36 microg/g. Three lung-targeting parameters were further assessed and showed that the microspheres had remarkable lung-targeting capabilities.