FDA Investigating Data on Zithromax Z-Pak Heart Risks

Following a recent study that suggested side effects of Zithromax (azithromycin) may increase the risk of cardiovascular death, federal drug regulators have indicated that they are reviewing the potential heart risks associated with the popular antibiotic, which is also known as Z Pack, Z-Pak or Zmax. 

In a statement issued yesterday, the FDA indicated that they were aware of the Zithromax study published in the New England Journal of Medicine on May 17, which found an increased risk of death associated with 5 day Zithromax treatment when compared to amoxicillin, Cipro or no antibiotic therapy. The agency said it will communicate any new information once its review is complete.

The study was conducted by Vanderbilt University researchers, who found that patients taking Pfizer’s Zithromax (azithromycin) were 2.5 times more likely to die of a heart-related problem than those taking amoxycillin. The results of the study suggest that doctors should prescribe other antibiotics for patients who are already known to have heart problems, especially problems that affect their heart rhythms.

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Zithromax Z-Pak belongs to a class of antibacterial drugs known as macrolides, which have been known to cause abnormal heart rhythm problems, including QT interval prolongation. That can lead to a fatal heart condition known as torsades de pointes. Zithromax was the only macrolide tested in the study.

The Zithromax label already carries a heart rhythm warning, after the FDA investigated all macrolides due to the problem in 2011.

The FDA has indicated that patients prescribed a Z-Pak should not stop taking their medication without speaking to their doctor, and recommended that healthcare provides be aware of the potential for QT prolongation and heart arrythmias when prescribing Zithromax or other macrolides.

Zithromax sales brought in more than $450 million for Pfizer in 2011. It is used to treat respiratory system and urinary tract infections, tonsillitis and other bacterial infections. It is also available as a generic.


  • CandiceMarch 3, 2014 at 3:44 pm

    I was taking this medicine last year

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