Changes in the pharmacokinetics of ciprofloxacin and fecal flora during administration of a 7-day course to human volunteers.
Twelve male subjects, aged 19 to 40 years, shown to be healthy by examination and laboratory tests, took 500 mg of ciprofloxacin every 12 h for 7 days. After the first and the last dose, blood and urine samples were taken and drug concentrations were determined by bioassay. There was a significant buildup in mean concentrations in serum from day 1 to day 7; mean peak levels (attained after 1 to 2 h) were 1.9 and 2.8 micrograms/ml, respectively. The terminal half-life was 3.5 to 4 h. About 40% of the drug was excreted into the urine during the 12-h period after dosing; minimum mean concentrations in urine were 105 micrograms/ml on day 1 and 174 micrograms/ml on day 7. Considerable amounts of ciprofloxacin were found in the feces on day 7 (185 to 2,220 micrograms/g). Marked changes in the aerobic part of the fecal flora were observed as a result of taking ciprofloxacin: coliforms were absent on day 7, and concentrations of streptococci and staphylococci were significantly reduced. There was no overgrowth by yeasts. One week later the fecal flora had returned to a state similar to that found before treatment. Anaerobes were little affected quantitatively but acquired resistance to ciprofloxacin. Side effects were mild and transient.
D000328:Adult; D000890:Anti-Infective Agents / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D002939:Ciprofloxacin; D004334:Drug Administration Schedule; D005243:Feces / Q000032:analysis / Q000382:microbiology*; D006801:Humans; D007700:Kinetics; D008297:Male; D011804:Quinolines / Q000009:adverse effects / Q000097:blood / Q000494:pharmacology* / Q000652:urine
D000890:Anti-Infective Agents; D011804:Quinolines; D002939:Ciprofloxacin