Multiple-dose ciprofloxacin dose ranging and kinetics

We injected multiple doses of intravenous ciprofloxacin over 10 minutes every 12 hours for 1 week to nine healthy subjects, while three other subjects received placebo. Ciprofloxacin doses of 25, 50, and 75 mg were evaluated with a 1-week washout between each dose level. Mean (+/- SD) terminal excretion t1/2S were 3.56 +/- 0.66, 4.15 +/- 0.68, and 3.46 +/- 0.42 hours for the 25, 50, and 75 mg doses. Serum clearances were 35.4 +/- 6.8, 31.8 +/- 3.0, and 31.3 +/- 5.4 L/hr/1.73 m2 for these doses. Urine concentrations remained above the minimal inhibitory concentration of most urinary tract pathogens for the full 12-hour dosing interval at each dose. Renal clearance accounted for 65% to 70% of the serum clearance, but because biologically active renally excreted metabolites have been identified, our values exceed the true values. The doses of ciprofloxacin we intravenously injected were well tolerated and appeared adequate for treatment of urinary tract infections. For serious hospital-acquired sepsis, however, larger doses should be evaluated.