CardioExchange Archive

A large observational study found no increased risk for cardiovascular events associated with azithromycin (Zithromax, Pfizer) in a general population of young and middle-age adults. In a paper published in the New England Journal of Medicine, Danish investigators report the results of a large national observational study comparing people who took azithromycin with matched controls who took no antibiotics and with controls who took penicillin V for similar indications.

Although there was a significant increase in the risk for death from cardiovascular causes in people taking azithromycin compared with people taking no antibiotics (RR 2.85, CI 1.13 – 7.24), there was no increase in risk when compared with people taking penicillin V (RR 0.93, CI 0.56 to 1.55). The findings, write the authors, indicate “that the increased risk that was observed in the comparison with no antibiotic use was entirely attributable to the risk of death associated with acute infection (or some other adverse health characteristic in persons receiving antibiotic treatment, as compared with those not treated with antibiotics) rather than with its treatment.”

The current study appears to contrast with an earlier study by Ray et al. which found a small increase in risk with azithromycin in people at high initial risk for cardiovascular disease. This was followed in March of this year by an FDA statement warning that QT prolongation associated with azithromycin can result in a potentially fatal arrhythmia. But, the Danish investigators write, their study provides “a clinically relevant complement to, rather than a contrast with, the findings of Ray et al.” They propose that azithromycin may increase risk in a population already at high cardiovascular risk but “this effect is not present in the general population.” They conclude:

 The implications of these findings for clinical decision making are reassuring; they indicate that for the general population of patients seen in office practice, azithromycin can be prescribed without concern about an increased risk of death from cardiovascular causes, whereas the benefits of therapy need to be weighed against the risk of death from cardiovascular causes among patients with a high baseline risk of cardiovascular disease.

In an accompanying perspective, FDA officials review the currently available evidence regarding the cardiovascular risk of azithromycin and other antibiotics. They recommend that “clinicians pause when they’re considering prescribing antibacterial drugs, especially for patients with preexisting cardiovascular risk factors or clinical conditions in which antibacterial drug therapy has limited benefits.”