Penetration of ciprofloxacin into bronchial secretions

The penetration of ciprofloxacin into bronchial secretions was evaluated in 21 patients after a single oral dose of 500 mg of ciprofloxacin. Ten successive serum samples were collected in the interval 0-12 h after administration, and bronchial samples were taken 2, 3, 4 and 6 h after administration. Concentrations were measured in all samples using a standard microbiological assay. The results showed that the kinetics in serum did not differ from those determined in previous studies, a peak level of 2.2 +/- 1.3 mg/l being achieved at 2 h followed by a slow decrease of the levels to 0.6 +/- 0.4 mg/l at 6 h. The bronchial concentrations reached about 0.5 mg/l at 2 h and remained stable until 6 h, ranging between 0.5 and 0.8 mg/l. The ratio between simultaneous bronchial and serum levels ranged from 0.19 at 2 h to 0.95 at 6 h. These data indicate that ciprofloxacin might be suitable for treatment of severe respiratory infections, especially pneumonia caused by Pseudomonas aeruginosa, since the MICs of ciprofloxacin for most bacteria involved in bronchopulmonary infections are very low and tissue diffusion of the drug in the respiratory tract is good.