In vitro and in vivo activity of antifungal agents in combination with fleroxacin, a new quinolone.

The in vitro and in vivo interaction of fleroxacin with amphotericin B (Amph B), flucytosine (5-FC) and azoles against Candida albicans strains was tested. In vitro the interaction between fleroxacin and various antifungals was not dependent on the incubation time. Fleroxacin neither enhances nor antagonizes the in vitro activity of Amph B at high concentration (50-100 micrograms/ml). Fleroxacin has a synergistic effect with ketoconazole (KETO), but this is not observed with itraconazole (ITRA) or fluconazole (FLU). In no instance antagonism was observed. The activity of 5-FC was antagonized by fleroxacin being generally reduced by 2-4 dilution steps. In murine candidosis the efficacies of all antifungal drugs were not influenced by addition of 100 mg/kg fleroxacin. Therefore, the effects seen in in vitro tests are most probably not relevant for the clinical use of a combination of fleroxacin with antifungal drugs.