Effect of short-term treatment with azithromycin on recurrent ischaemic events in patients with acute coronary syndrome in the Azithromycin in Acute Coronary Syndrome (AZACS) trial: a randomised controlled trial

Background There is serological and epidemiological evidence of an association between Chlamydia pneumoniae infection and coronary artery disease. Results of previous smaller studies have indicated a reduction of recurrent ischaemic events in patients with acute coronary syndrome when given macrolide antibiotics. We aimed to assess whether short-term treatment with the macrolide antibiotic azithromycin reduces recurrent ischaemic events in patients admitted for unstable angina or myocardial infarction. Methods We assessed the effect of azithromycin in a multicentre, double-blind randomised trial in 1439 patients with unstable angina or acute myocardial infarction. Patients were randomly allocated to receive 500 mg azithromycin on the first day after randomisation, followed by 250 mg daily for 4 days or placebo. Patients were followed up for 6 months. The primary endpoints were death, recurrent myocardial infarction, or recurrent ischaemia necessitating revascularisation. Analysis was done by intention to treat. Findings Treatment with azithromycin did not result in reduction of either individual endpoints or any of the primary endpoints. Of the 716 patients in the azithromycin group, 23 (3%) died, 17 (2%) developed myocardial infarction, 65 (9%) had recurrent ischaemia needing revascularisation, and 100 (14%) had one or more of these endpoints. In the placebo group (n=723) the corresponding numbers of patients were 24 (4%), 22 (3%), 59 (8%), and 106 (15%), respectively (p=0.664, 95% CI 0.72-1.24). 62 (9%) of patients in the azithromycin group and 59 (8%) in the placebo group reached the secondary endpoint of ischaemia or congestive heart failure necessitating admission (difference 0.5%, 95% CI 0.75-1.53; p=0.707). We recorded few side-effects. Interpretation Short-term treatment with azithromycin does not reduce development of recurrent events in patients with acute coronary syndrome.