(HealthDay News) — Patients using QT-prolonging drugs have an increased risk for cardiac events in association with azithromycin versus amoxicillin, according to a study published online in JAMA Network Open.

Haridarshan Patel, PharmD, PhD, from the University of Illinois at Chicago, and colleagues conducted a retrospective cohort study to compare the odds of cardiac events among new users of azithromycin versus amoxicillin. The final cohort included 4,282,570 patients with 2,141,285 episodes of each index therapy.

The researchers found that within 5 days after initiation of therapy, there were 1474 cardiac events (708 and 766 in the amoxicillin and azithromycin cohorts, respectively). The 2 most frequently reported events were syncope and palpitations (70 and 22.5%, respectively). At 5, 10, and 30 days, the odds of cardiac events were not significantly higher for azithromycin versus amoxicillin (odds ratios [95% confidence intervals]: 1.08 [0.98 to 1.20], 1.05 [0.97 to 1.15], and 0.98 [0.92 to 1.04], respectively). The odds of cardiac events were increased with azithromycin versus amoxicillin for patients receiving any concurrent QT-prolonging drug (odds ratio, 1.40; 95% confidence interval, 1.04 to 1.87). No increased risk for cardiac events was seen with azithromycin for patients aged 65 years or older and those with a history of cardiovascular disease and other risk factors.

“Our findings should give researchers and clinicians looking at azithromycin as a potential treatment for COVID-19 pause,” Patel said in a statement.

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Two authors disclosed financial ties to the biopharmaceutical industry.


Patel H, Calip GS, DiDomenico RJ, et al. Comparison of cardiac events associated with azithromycin vs amoxicillin. JAMA Netw Open. doi:10.1001/jamanetworkopen.2020.16864