Objective: To compare the ratio of the area under the concentration-time curve at 24 hours to the minimum inhibitory concentration value (24-h AUC/MIC) of ciprofloxacin between 400 mg intravenously every 8 h and 400 mg intravenously every 12 h.
Material and method: A prospective, randomized, two-way crossover study of 10 patients with gram-negative bacilli bacteremia was conducted. All patients were randomized to receive ciprofloxacin in both regimens consecutively: (i) 400 mg intravenously every 8 h for four doses; (ii) 400 mg intravenously every 12 h for four doses. Ciprofloxacin pharmacokinetic studies were carried out after the start of both regimens.
Results: For the ciprofloxacin 400 mg intravenously every 8 h regimen, the 24-h AUC/MIC at MICs of 0.5 and 1 microg/ml were 218.63 +/- 78.75 and 109.31 +/- 39.37, respectively. For the ciprofloxacin 400 mg intravenously every 12 h regimen, the 24-h AUC/MIC at MICs of 0.5 and +/- microg/ml were 144.07 +/- 57.02 and 72.03 +/- 28.51, respectively. After 14 days of ciprofloxacin treatment, the gram-negative bacilli infections were eradicated in all patients. Moreover, during both regimens, no adverse events related to the use of ciprofloxacin were observed.
Conclusion: Both ciprofloxacin 400 mg every 8 h and 400 mg every 12 h regimens can provide good coverage for pathogens with the susceptibility breakpoint of ciprofloxacin with an MIC of 0.5 microg/ml. For pathogens with an MIC of 1.0 microg/ml, only ciprofloxacin 400 mg every 8 h regimen can provide a 24-h AUC/MIC ratio greater than 100.