Piperacillin and tobramycin in the treatment of Pseudomonas lung infections in cystic fibrosis.

Fourteen children with cystic fibrosis and pulmonary lung infection due to Pseudomonas aeruginosa were treated with piperacillin (300 mg/kg/day) alone or piperacillin and tobramycin (7 mg/kg/day) iv. The outcome with respect to clinical state, chest X-ray and lung function tests was better with combination therapy than with piperacillin alone. Bacteriological response was the same with both regimens: leucocyte content of the sputum decreased, non-mucoid Ps. aeruginosa strains were eliminated, but mucoid strains were only suppressed (11 children). Peak serum levels of piperacillin averaged 102 mg/l, the overall serum elimination was 0.75 h and the mean sputum concentrations ranged from 1.07 to 2.2 mg/l. Peak serum levels of tobramycin averaged 5.15 mg/l, the half life was 1.25 h and the mean sputum concentrations ranged from 0.57 to 0.68 mg/l. The clearance of piperacillin and tobramycin was increased significantly. Drug-resistance did not develop during therapy.