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Azithromycin treatment outcomes may differ based on antibiotic type

Patients with cystic fibrosis saw a greater increase in FEV₁ when given oral azithromycin in combination with certain IV antibiotics for the treatment of Pseudomonas aeruginosa, as well as an increased overall improvement of FEV₁, according to a study published in Annals of the American Thoracic Society.

Researchers, however, were unable to determine any association between treatment combinations analyzed in this study.

According to the study, patients treated with combination azithromycin and IV colistimethate saw a +3% relative FEV₁ recovery and a 2% overall improvement.

Those treated with combination azithromycin and IV tobramycin for P. aeruginosa experienced a –3% recovery of FEV₁ as well as a –2.64% overall improvement.

“Our findings, although inconclusive and unable to establish a causal relationship, suggest that concomitant azithromycin may be unhelpful when combined with intravenous tobramycin — a pattern of interaction that we have observed in vitro, in animal studies, and in the context of inhaled antipseudomonal therapies,” the researchers wrote.

In this retrospective cohort study, researchers analyzed the use of azithromycin in combination with IV colistimethate or tobramycin for the treatment of pulmonary exacerbation caused by P. aeruginosa in patients with cystic fibrosis.

The primary outcome was total lung function recovery as measured by FEV₁ following treatment.

According to the findings, 220 exacerbation events occurred in 121 patients in the tobramycin group, of which 47% of treatments included azithromycin. In the colistimethate group, 207 exacerbation events occurred in 86 patients, of which 59% were receiving treatment that included azithromycin.

“Our analyses, although inconclusive and unable to infer causality, suggest that chronic azithromycin treatment may provide modest additional benefit during intravenous antibiotics to treat a pulmonary exacerbation in those treated with a colistimethate-based drug regimen but not when intravenous tobramycin is used,” the researchers wrote. “Whether or not azithromycin use directly influenced the antimicrobial effects of intravenous colistimethate or intravenous tobramycin cannot be understood from these data.”

The investigators stated that more research is needed to determine whether azithromycin alters the efficacy of IV antibiotics used in the treatment of P. aeruginosa. – by Scott Buzby

Disclosure: Healio Pulmonology could not confirm relevant financial disclosures at the time of publication.