Azlocillin and gentamicin in respiratory tract infections with Pseudomonas aeruginosa in patients with cystic fibrosis

Azlocillin, 200 mg/kg bodyweight every 8 h, and gentamicin, 2.5-4 mg/kg bodyweight every 12 h, in combination were given intravenously to 10 patients with cystic fibrosis for at least 10 days. The patients were colonized with Pseudomonas aeruginosa and were hospitalized due to symptoms of lower respiratory tract infections. Using an agar well diffusion method the antibiotic concentrations were followed in serum and sputum. The individual sputum concentration of azlocillin varied during 4 h after administration from less than 1.5 to 38 micrograms/ml. The sputum concentration of gentamicin varied from 0.3 to 1.1 micrograms/ml. P. aeruginosa was apparently eliminated in 3 patients. The concentration of the antibiotics in sputum could not predict the outcome of treatment. All patients improved subjectively. No adverse effect was seen.