Data on the effects of long-term treatment with azithromycin (AZM) on inflammatory markers in cystic fibrosis patients chronically infected with Pseudomonas aeruginosa are scarce. So far there is no pharmacokinetic and clinical data on once-weekly dosage of AZM in CF patients.

In a randomised double-blind, placebo-controlled trial, patients received AZM or placebo 1 per week for 8 weeks (AZM dosage – 20–29kg: 500mg, 30–39kg: 750mg, 40–49kg: 1000mg and ≥50kg: 1250mg) after a course of intravenous antipseudomonal antibiotics. Pulmonary function tests, the serum markers LPS-binding protein (LBP), interleukin-8 (IL-8), CRP, P. aeruginosa alginate in sputum samples and quality of life scores were evaluated.

Thirty-eight patients (21 AZM/17 placebo) (mean age: 23.7 years; mean FEV₁: 62% of predicted) were recruited. After treatment (mean dose of 21.2mg/kg body weight once a week) pulmonary function declined in both groups compared to baseline (i.e. after cessation of IV antibiotics). The AZM group was significantly better for mean changes in serum CRP (AZM: +0.9mg/l, placebo: +21.6mg/l, p=0.019), lipopolysaccharide binding protein in serum, LBP (AZM: +0.9μg/ml, placebo: +7.0μg/ml, p=0.015), serum interleukin-8 (AZM: −3.1pg/ml, placebo: +2.9pg/ml, p=0.001) and alginate in sputum (AZM: +85μg/ml, placebo: +353μg/ml, p=0.048). Quality of life was significantly better after AZM and there was no increase in treatment-related adverse events.

Once-weekly azithromycin ameliorated inflammatory reactions and improved quality of life. A decline of pulmonary function after cessation of IV antibiotics could not be prevented.