In vitro characterization of ciprofloxacin distribution in rat lung

The binding of ciprofloxacin to both lung homogenate and isolated subcellular fractions, as well as the washout kinetics from lung homogenate of rats, was studied in vitro. Differences in the binding capacity of ciprofloxacin to subcellular fractions and total lung homogenate were observed. In vitro mean partition coefficient values (+/- SD) for nuclear, mitochondrial and microsomal fractions were 2.84 +/- 0.82, 2.32 +/- 0.69 and 2.72 +/- 0.75, respectively, with no statistical differences among these values. On the other hand, the partition coefficient obtained with lung homogenate showed a mean value (+/- SD) of 1.39 +/- 0.31, statistically lower than the values corresponding to the different cellular fractions. These results reveal a great affinity of ciprofloxacin for intracellular structures that may condition the distribution characteristics of the quinolone in lung and other body tissues, In washout studies, washout of ciprofloxacin from lung homogenate proved to be a monoexponential and first-order kinetic process.