Comparative activities of pefloxacin and ciprofloxacin in the treatment of chronic respiratory tract infections.

To determine the efficacy in vivo of pefloxacin and ciprofloxacin in the treatment of acute infectious bronchopneumopathies, 90 patients, suffering from acute exacerbation of chronic bronchitis and with no known allergies to quinolones, were admitted to the study. Patients were randomly divided into three groups of 30; the first group was dosed with pefloxacin 800 mg i.v. every 24 hours; the second group with pefloxacin 800 mg per os every 24 hours and the third with 500 mg per os of ciprofloxacin every 12 hours. Blood and bronchial secretion samples were simultaneously collected 2, 4, 8, 12, 14 and 24 hours after the first daily dose of antibiotic. Serum and bronchial secretion concentrations of pefloxacin and ciprofloxacin were determined by using a microbiological agar disk diffusion assay, employing Escherichia coli Kp 712 as test organism. Eradication of responsible microorganisms (Staphylococcus aureus, Haemophilus influenzae, Moraxella catarrhalis) were achieved in 98% of patients around 72 hours post treatment. Generally, both antibiotics expressed similar bactericidal properties when orally administered, while intravenous administration of pefloxacin displays a more rapid antibacterial action in comparison with the oral administration schedules. Maximal concentrations of both drugs in bronchial secretion were recorded at the same time after treatment (4 hours), with concentrations of about 2.5 micrograms/ml. Pefloxacin, having a longer half-life, was found 24 hours post-treatment with plasma concentrations of 1.5 micrograms/ml following a single oral dose of 800 mg. Ciprofloxacin, having a shorter half-life, showed a peak of about 1 microgram/ml, 12 hours after administration (500 mg/12 hours/os).