AIM\ The purpose is to optimize the preparation of sustained release
microspheres of erythromycin using the biodegradable
materials
polylactic acid (PDLLA) for lung targeting. METHEDS\ The orthogonal test design was used to optimize the technology of preparation with good reproducibility. The surface morphology of the
microspheres was observed by scanning electron microscope. The formation of the drug microspheres was confirmed with DSC. The mean diameter and the size distribution of microspheres, the drug loading,the incorporation efficiency,the reappearances of pharmaceutical technology,drug release \%in vitro\%, stability and tissue distribution after intravenous administration were examined. RESULTS\ Erythromycin polylactic acid microspheres were regular in their morphology. Drug was enveloped in microspheres but not physically mixed with PDLLA. The average particle size was 11.65 μm with over 94% of the microspheres being in the range of 5~20 μm;the drug loading and the encapsulated ratio were 18% and 60% respectively. The reappearance of pharmaceutical technology was good. The microspheres were stable for three months at 4℃ and room temperature. The \%in vitro\% release properties could be expressed by the Higuchi′s equation: \%y=28.067+3.8515t\+\{1/2\} (r\%=0.9834). Compared with injective solution, the drug in microspheres was more concentrated in lung tissue. CONCLUSION\ The technology of preparation was successful and erythromycin polylactic acid microspheres showed significant sustained release and lung targeting.