Azithromycin concentrations in serum and bronchial secretions of patients with cystic fibrosis

Objective: To measure azithromycin (AZM) concentrations in serum and bronchial secretions in patients with cystic fibrosis (CF) and chronic Pseudomonas aeruginosa pulmonary infection. Patients and Methods: 10 CF patients (four male, six female; mean age 29 +/- 10 years) with chronic P aeruginosa pulmonary infection were randomised to receive either 500 or 1000mg of AZM (five patients per group) orally once daily for 5 days. Concentrations of AZM in serum and bronchial secretions (obtained after physiotherapy) were evaluated every 24 hours for the 5 days of administration and the following 6 days. Main Outcome Measures and Results: High AZM concentrations were found in bronchial secretions, persisting after drug administration had ended. Mean concentrations were greater than or equal to4 mg/L for the 1000 mg/day dose from day 2 to 11 and >2 mg/L for the 500 mg/day dose from day 2 to day 10. Serum AZM concentrations were much lower (<0.4 mg/L for the 1000 mg/day, and <0.2 mg/L for the 500 mg/day, dosage). Conclusions: These data appear to indicate the possibility of obtaining in vivo AZM concentrations previously shown to inhibit production of virulence factors in Fl aeruginosa in vitro. We consider that clinical trials evaluating prolonged administration of AZM to CF patients would be both useful and justifiable.