Approximately five million people die annually from acute respiratory tract infections (eg, acute bronchitis, acute exacerbations of chronic bronchitis), with pneumonia being the most frequent cause of death, hospitalization, and medical consultation. In a new review published in the Cochrane Library, researchers sought to compare the effectiveness of the macrolide antibiotic azithromycin to the broad-spectrum penicillin amoxicillin or amoxicillin/clavulanic acid (broad-spectrum penicillin + beta-lactamase inhibitor) for the treatment of lower respiratory tract infections. Microbial eradication, clinical failure, and adverse events were assessed for all therapies.

Fifteen trials, involving 2496 patients, were included in the assessment (12 trials compared azithromycin to amoxicillin-clavulanic acid; three studies compared azithromycin to amoxicillin). The following is a summary of the findings:

Pooled analysis:

  • Incidence of clinical failure on day 10–14: azithromycin group 10.1% vs. amoxicillin or amoxicillin-clavulanic acid 10.3%; no statistical significance between the two groups (risk ratio [RR]:1.09)
  • Microbial eradication: azithromycin group: 66.4% vs. amoxicillin or amoxicillin-clavulanic acid 67.6%; no significant difference between the groups
  • Overall incidence of adverse events: azithromycin group: 17.9% vs. amoxicillin or amoxicillin-clavulanic acid: 23.6% (RR: 0.76)

Subgroup analysis:

  • No significant difference in effect between the two groups with regards to age
  • For acute bronchitis, incidence of clinical failure significantly lower in the azithromycin group (RR:0.63)

The authors conclude that while evidence may be unclear as to whether azithromycin is superior to amoxicillin or amoxicillin-clavulanic acid in treating acute lower respiratory tract infections, for patients with acute bronchitis with suspected bacterial cause, azithromycin appears to be the more effective choice for lowering incidence of clinical failure. Also, the incidence of adverse events seems lower with azithromycin.  For clinicians treating acute lower respiratory tract infections, other factors such as cost, convenience, and treatment adherence should be taken into consideration.