EX-VIVO ANTIBACTERIAL PROPERTIES OF RUFLOXACIN COMPARED WITH THOSE OFNORFLOXACIN IN A STUDY WITH HEALTHY-VOLUNTEERS

Twelve adult males participated in a randomized crossover phase I clin ical trial comparing serum bactericidal titers (SBTs), urine bacterici dal titers (UBTs), and urine killing rates (UKRs) against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213, after the admini stration of single 400-mg doses of rufloxacin and norfloxacin at diffe rent times up to 72 h postdose. SBTs were significantly higher (P < 0. 05) against E. coli from 8 to 48 h and against S. aureus from 4 to 24 h with rufloxacin. UBTs for E. coli were higher (P < 0.05) for norflox acin at early sample times (0 to 8 h) but higher for rufloxacin (P < 0 .05) at sample times from 16 h on for both E. coli and S. aureus. Simi lar UKRs were obtained for both quinolones for 0 to 2 h and 8 to 12 h, but the UKR was maintained for 72 h with rufloxacin. The high and sus tained mean levels of rufloxacin in urine (>35 mu g/ml), median UBTs ( >32 for E. coli and 16 for S. aureus) and UKRs for E. coli suggest pro longed urine antibacterial activity (for at least 72 h) and its use as a single 400-mg dose in the treatment of uncomplicated cystitis.