Twelve volunteers received a single oral dose of 1,000 mg extended-release (XR) ciprofloxacin versus 500 mg levofloxacin to assess urinary bactericidal titers (UBTs) against common uropathogens. Areas under UBT-time curves were significantly larger for Proteus mirabilis with XR ciprofloxacin and for staphylococci with levofloxacin.Complicated urinary tract infections (UTIs) are caused by gram-negative and -positive uropathogens (25). Fluoroquinolones are among the drugs of choice for empirical antibiotic therapy. They differ, however, in pharmacokinetic properties (11) and in antibacterial activity, and their antibacterial activity in urine is reduced significantly depending on urine pH and contents (6, 15). Extended-release (XR) ciprofloxacin and levofloxacin are given once daily (12,23). The purpose of this study was to compare the ex vivo pharmacokinetic/pharmacodynamic properties, including urinary bactericidal titers (UBTs) of a single oral dose of 1,000 mg extended-release ciprofloxacin versus 500 mg levofloxacin against common uropathogens. The pharmacokinetic aspects of this study were recently published (24).Twelve healthy volunteers successively received one oral dose of 1,000 mg extended-release ciprofloxacin (Bayer Vital GmbH, Wuppertal, Germany) or 500 mg levofloxacin (SanofiAventis, Berlin, Germany) in a crossover design at an interval of 7 days according to the randomization schedule. All voided urine samples were collected over a 12-h interval prior to drug administration (to obtain antibiotic-free urine from each individual) and at the following time intervals after administration of the drug: 0 to 4, 4 to 8, 8 to 12, 12 to 16, 16 to 24, 24 to 28, 28 to 32, and 32 to 36 h. All samples were stored at Ϫ20°C. Levofloxacin and ciprofloxacin were analyzed in one chromatographic run by high-pressure liquid chromatography. The drug concentrations in serum and urine samples were measured by comparison with a serum and urine calibration row, respectively (24). MICs, minimal bactericidal concentrations (MBCs), and urinary bactericidal titers were determined as published previously (17,26).The bacterial strains used in this study and ciprofloxacin and levofloxacin MICs are depicted in Table 1. The MBCs of levofloxacin and ciprofloxacin were similar to the corresponding MICs for all strains tested. The area under the 24-h UBTversus-time curve (AUBC) (13) was calculated as the sum of the reciprocal UBT values and the respective time intervals for each test organism and for each drug. Laboratory, UBT, and AUBC data for the two drugs were compared for each individual by the paired t test. The application of the paired t test appears adequate according to our previous analysis of the respective residuals (16). An ␣ value of 0.05 was determined to be statistically significant. Due to the high number of tests performed, the results are of descriptive nature only. The clinical significance of the statistical results, however, should be evaluated. Statistical calculations were performed using the Microsoft Excel 97...
