Bactericidal activity of ciprofloxacin in serum and urine against Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus and Streptococcus faecalis

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Abstract
Ten volunteers received three doses of 500 mg ciprofloxacin, orally every 12 hours. After the last dose, mean serum levels were (mg/1 ± sd) 2·4 ± 0·83 at 1 h; 0·91 ± 0·30 at4 h and 0·18 ± 0·04 at 12 h. At 1 h the median serum bactericidal activity was satisfactory only against the Echerichia coli (1:256) and Klebsiella pneumoniae (1:128). In urine collected from 0 to 4 h and 8 to 12 h after the last dose, the mean ciprofloxacin level was respectively 482·5 ± 324·7 and 80·9 ± 48·2 mg/1 ± SD. Bactericidal activity in urine was high even against the least susceptible species tested: Pseudomonas aeruginosa, Staphylococcus aureus and Streptococcus faecalis. A post antibiotic effect was demonstrated in 22 out of the 29 strains tested, ranging mainly from 1 to 3 h. Ciprofloxacin 500 mg orally twice a day is a bactericidal regimen against a wide range of urinary pathogens but has a limited systemic activity.