Comparative pharmacokinetics of ciprofloxacin and ofloxacin in cystic fibrosis patients.

The steady state pharmacokinetic properties of ciprofloxacin and ofloxacin were compared in cystic fibrosis patients. In a cross-over study eighteen adult patients with chronic Pseudomonas aeruginosa lung infection were given either oral ciprofloxacin 750 mg bid or oral ofloxacin 400 mg bid for two weeks. Three months later the alternative treatment was given. Concentrations were determined by a microbiological assay. Mean serum concentrations of ofloxacin (peak 5.9 mg/l) were higher than for ciprofloxacin (peak 4.0 mg/l). The time to reach maximal concentrations did not differ. The apparent total body clearance was significantly greater for ciprofloxacin, but renal clearances were similar. Relative to ofloxacin ciprofloxacin had a significantly shorter serum elimination half-life (3.4 vs. 6.4 h), showed less penetration into sputum (18% vs. 79%) and a lesser amount was recovered in urine (21% vs. 71% up to 12 h after dosing). No correlation was found between any pharmacokinetic parameter and change in pulmonary function.