Penetration of ciprofloxacin into human pleural fluid.

The concentrations of ciprofloxacin (1.5 mg/kg of body weight) in serum and in uninfected pleural exudates were studied after one and three intravenous injections had been given at 8-h intervals. The drug was assayed in serum and in pleural fluid by high-performance liquid chromatography. The peak concentrations in pleural fluid 1.5 h after one and three injections were (mean +/- standard error of the mean) 0.52 +/- 0.09 and 0.77 +/- 0.15 mg/liter, respectively; the corresponding 8-h concentrations were 0.19 +/- 0.05 and 0.39 +/- 0.10 mg/liter. At 1 and 8 h, the ratios of mean concentrations in pleural fluid to mean concentrations in serum were 112 and 158%, respectively, after one injection and 77 and 122% after three injections. This study suggested that there is a satisfactory pleural penetration of ciprofloxacin after intravenous injection.