Ciprofloxacin in the treatment of Pseudomonas infection in cystic fibrosis patients.

Ten patients with cystic fibrosis received 19 therapeutic courses of ciprofloxacin at a dose of 750 mg orally twice daily. The length of therapy ranged from two to five weeks except for one patient who was treated for six weeks. The mean peak serum concentration of ciprofloxacin was 3.41 mg/l and the mean trough level was 1.11 mg/l. For comparison nine patients were treated with the combination of azlocillin at a dose of 350 mg/kg/day in four divided doses and tobramycin at an initial dose of 9 mg/kg/day in three divided doses. All patients were infected with Pseudomonas aeruginosa except for one patient in whom P. cepacia grew in the sputum cultures; the MICs of ciprofloxacin ranged from 0.05 to 1.56 mg/l. The results obtained with these two therapeutic regimens were comparable. The patient treated for P. cepacia infection developed resistance to ciprofloxacin (MIC greater than 6.24 mg/l) during the course of treatment. Ciprofloxacin appears to be an alternative treatment to the use of an aminoglycoside and a penicillin in cystic fibrosis patients.