Urinary pharmacodynamics of low-dose ciprofloxacin and ofloxacin

The incidence of resistant uropathogens to the fluoroquinolones is increasing, but their effectiveness in the urine against these strains is unknown. In this investigation, we studied the urinary pharmacodynamics of ciprofloxacin (100 mg) and ofloxacin (200 mg) against urinary isolates that were moderately resistant to ciprofloxacin (Escherichia coli, MIC = 4; Klebsiella pneumoniae, MIC = 4. Staphylococcus saprophyticus, MIC = 8) and ofloxacin. Seven healthy female volunteers received three doses (one dose every 12 h) of ciprofloxacin and ofloxacin in a randomized, crossover design with a 1-week washout period between regimens. Urine bactericidal activity was determined after the first and third dose of each drug. Both ciprofloxacin and ofloxacin exhibited prolonged (> or = 6 h) urine bactericidal activity against the E. coli and K. pneumoniae isolates after the first dose. No bactericidal activity was demonstrated for ciprofloxacin against the S. saprophyticus strain. In contrast, ofloxacin exhibited urine bactericidal activity for 8 h against this isolate. Similar findings were observed after the third dose, with the exception that ciprofloxacin exhibited a short period (4 h) of bactericidal activity against the S. saprophyticus strain. In summary, low-dose regimens of ciprofloxacin and ofloxacin exhibited prolonged bactericidal activity against moderately resistant strains of common bacterial uropathogens. Only ofloxacin demonstrated bactericidal activity in the urine during the first dosing interval against a moderately resistant isolate of S. saprophyticus.