Long-term benefits of inhaled tobramycin in adolescent patients with cystic fibrosis

Study objective: To determine the effect of long-term suppression of Pseudomonas aeruginosa on lung function and other clinical end points in adolescent patients with cystic fibrosis (CF). Design: Two identical, randomized, placebo-controlled trials followed by three open-label follow-on trials. Setting: Sixty-nine CF study centers in the United States. Interventions: Active drug consisting of a 300-mg tobramycin solution for inhalation (TSI). Patients: One hundred twenty-eight adolescent CF patients (aged 13 to 17 years) with P aeruginosa and mild-to-moderate lung disease (FEV1 percent predicted greater than or equal to 25% and less than or equal to 75%). Measurements: Pulmonary function, P aeruginosa colony forming unit density, incidence of hospitalization and IV antibiotic use, weight gain, and aminoglycoside toxicity were monitored. Results: At the end of the first three 28-day cycles of TSI treatment, patients originally randomized to TSI and placebo treatments exhibited improvements in FEV1 percent predicted of 13.5% and 9.4%, respectively. FEV1 percent predicted was maintained above the value at initiation of TSI treatment in both groups. At the end of the last "on-drug" period (92 weeks), patients originally randomized to TSI and placebo treatments showed improvements of 14.3% and 1.8%, respectively. Improvement in pulmonary function was significantly correlated with reduction in P aeruginosa colony forming unit density (p = 0.0001). The average number of hospitalizations and IV antibiotic courses did not increase over time. TSI treatment was associated with increased weight gain and body mass index. P aeruginosa susceptibility to tobramycin decreased slightly over time, but this was not correlated with clinical response. Conclusions: TSI treatment improved pulmonary function and weight gain in adolescent patients with CF over a 2-year period of long-term, intermittent use.