Zithromax May Increase Heart Risks When Used With Other Drugs That Affect Heart Rhythm: Study

The findings of a new study suggest that side effects of the antibiotic Zithromax may increase the risk of serious heart problems when combined with QT-prolonging medications.

As the global COVID-19 pandemic has worsened, recent attention has focused on Zithromax as a possible treatment. However, this research highlights the potential cardiovascular side effects, including increased risk of death.

In a study published in the journal JAMA Network Open on September 15, researchers from the University of Illinois at Chicago focused on side effects of Zithromax (azithromycin) and amoxicillin. Both drugs are antibiotics used to treat infections. However, Zithromax has been touted by some as a possible treatment for COVID-19.

Researchers used data from the Truven Health Analytics MarketScan database of more than 4 million patients. Data was collected from January 1, 2009, to June 30, 2015. Patients using Zithromax were matched to those using amoxicillin.

Within five days of taking the antibiotics there were nearly 1,500 episodes of cardiac events, including fainting, heart palpitations, and cardiac arrest, researchers found. There were 708 events among the amoxicillin group and 766 in the Zithromax group.

The risk of suffering cardiac events with Zithromax compared with amoxicillin were not significantly higher at 5, 10, or 30 days after taking the drug compared to the amoxicillin group. Even among patients 65 years and older those with a history of cardiovascular disease and other risk factors, there was no increased risk of cardiac events if they were taking Zithromax. However, researchers noticed an increased risk of cardiac side effects among patients taking Zithromax together with QT-prolonging drugs.

QT-prolonging drugs are medications that affect the electrical impulses of the heart. They affect the electrical rhythm call the QT interval. These drugs include some antidepressants, anti-malaria drugs like hydroxychloroquine, also suggested as a COVID-19 treatment, and blood pressure medications such as ACE inhibitors and beta-blockers.

Patients who were taking QT-prolonging drugs and Zithromax had a 40% increased risk of suffering a cardiac event compared to patients taking amoxicillin.

The two most frequent cardiac events were syncope, or fainting, and heart palpitations.

These findings may be in line with another study published in 2017, which indicated there was no increased risk of heart rhythm side effects in patients taking Zithromax. That may be because the increased risk only occurs when concurrently taken with other drugs.

While overall, the risk of heart attack or other heart side effects was the same between the two antibiotic drugs, the risk of cardiac side effects increased if the patient was taking QT-prolonging drugs.

“This study found no association of cardiac events with azithromycin compared with amoxicillin except among patients using other QT-prolonging drugs concurrently,” wrote study authors. “Although azithromycin is a safe therapy, clinicians should carefully consider its use among patients concurrently using other QT-prolonging drugs.”