Ulifloxacin is a new
quinolone antibiotic and it is effective against
pneumonia. We previously showed that it is highly distributed into the epithelial lining fluid (ELF) in rats, which might be resulting from certain active transport. The transport system has not been, however, clarified yet. In this study, we attempted to characterize the distribution mechanism of
ulifloxacin into the rat ELF. We also aimed to elucidate the feature of
ulifloxacin uptake in rat lung and human
lung adenocarcinoma cells (Calu-3). In infusion studies,
ulifloxacin concentrations in the ELF and lung were higher than that in the plasma, and decreased by co-administration of
sparfloxacin or
azithromycin to the level of plasma concentration. Integration plot analysis showed that active uptake of
ulifloxacin from the plasma to lung was also inhibited by
sparfloxacin and
azithromycin. In in vitro studies, time and temperature-dependent uptake into Calu-3 was observed, and this uptake was inhibited by
sparfloxacin and
azithromycin as observed in the rat lung. Additionally
sparfloxacin inhibited the active uptake of
ulifloxacin into Calu-3 more strongly than
levofloxacin as observed in the rat lung. These results suggest that active uptake of
ulifloxacin from the plasma to lung controls the distribution of
ulifloxacin from the plasma to ELF, and that the uptake of
ulifloxacin into Calu-3 has partly similar characteristics to its uptake into the rat lung. We believe our study will contribute to much better understanding of
antibiotic efficacy against pathogens which cause
pneumonia.