Antibacterial activity of ciprofloxacin administered intravenously in a pharmacodynamic in vitro model

The antibacterial activity of ciprofloxacin against Gram-positive and Gram-negative bacteria was evaluated in an in vitro model by simulating its pharmacokinetics following a single 100 or 200 mg administration intravenously. The one compartment open model described by Grasso and coworkers was used for these experiments. Ciprofloxacin concentrations in the model were reproduced by calculations based on the concentration-time curve in human volunteers as reported by Wise and others. The maximum reduction of viable cell count for Enterococcus faecalis and Staphylococcus aureus was from two-to three-orders of magnitude; for Pseudomonas aeruginosa and Enterobacter cloacae from four to seven orders. A rapid killing was recorded both for Gram-positive and Gram-negative bacteria, but the initial killing was more prolonged and more pronounced for the higher dosage. The last did not interfere with regrowth that occurred for all strains after eight hours.