Azithromycin for acute lower respiratory tract infections

Acute lower respiratory tract infections (LRTI) range from acute bronchitis and acute exacerbations of chronic bronchitis to pneumonia. Approximately five million people die of acute respiratory tract infections annually. Among these, pneumonia represents the most frequent cause of mortality, hospitalization and medical consultation. Azithromycin is a new macrolide antibiotic, structurally modified from erythromycin and noted for its activity against some gram-negative organisms associated with respiratory tract infections, particularly Haemophilus influenzae (H. influenzae).

To compare the effectiveness of azithromycin to amoxycillin or amoxycillin/clavulanic acid (amoxyclav) in the treatment of LRTI, in terms of clinical failure, incidence of adverse events and microbial eradication.

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2007 Issue 2), MEDLINE (January 1966 to July 2007), and EMBASE (January 1974 to July 2007).

Randomized and quasi-randomized controlled trials, comparing azithromycin to amoxycillin or amoxycillin/clavulanic acid in participants with clinical evidence of acute LRTI: acute bronchitis, pneumonia, and acute exacerbation of chronic bronchitis were studied.

The criteria for assessing study quality were generation of allocation sequence, concealment of treatment allocation, blinding, and completeness of the trial. All types of acute LRTI were initially pooled in the meta-analyses. The heterogeneity of results was investigated by the forest plot and Chi-square test. Index of I-square (I(2)) was also used to measure inconsistent results among trials. Subgroup and sensitivity analyses were conducted.

Fifteen trials were analysed. The pooled analysis of all trials showed that there was no significant difference in the incidence of clinical failure on about day 10 to 14 between the two groups (relative risk (RR), random-effects 1.09; 95% confidence interval (CI) 0.64 to 1.85). Sensitivity analysis showed a reduction of clinical failure in azithromycin-treated participants (RR 0.55; 95% CI 0.25 to 1.21) in three adequately concealed studies, compared to RR 1.32; 95% CI 0.70 to 2.49 in 12 studies with inadequate concealment. Twelve trials reported the incidence of microbial eradication and there was no significant difference between the two groups (RR 0.95; 95% CI 0.87 to 1.03). The reduction of adverse events in the azithromycin group was RR 0.76 (95% CI 0.57 to 1.00).

There is unclear evidence that azithromycin is superior to amoxicillin or amoxyclav in treating acute LRTI. In patients with acute bronchitis of a suspected bacterial cause, azithromycin tends to be more effective in terms of lower incidence of treatment failure and adverse events than amoxicillin or amoxyclav. Future trials of high methodological quality are needed.