Effects of fleroxacin on HeLa cell functions and topoisomerase II.

The effects of fleroxacin and other new 4-quinolones on cellular functions and topoisomerase II of HeLa cells were investigated. The potency of cytotoxicity increased in the order fleroxacin less than nalidixic acid less than ofloxacin less than norfloxacin less than ciprofloxacin. The cytotoxicity was well correlated with inhibitory effects of 4-quinolones on topoisomerase II. However, the cytotoxicity did not correlate with antibacterial activity, and cytotoxicity was observed only at greater than 100-fold higher concentrations than the minimum inhibitory concentrations of new 4-quinolones for Enterobacteriaceae. Judging from the serum levels attainable after oral administration, new 4-quinolones, especially fleroxacin, will have little effect on topoisomerase in eukaryotic cells.