FDA Warns Public About Zithromax (Z-pack) Heart Risks

The U.S. Food and Drug Administration (FDA) warned on Tuesday that the popular antibiotic azithromycin, sold as Zithromax, or Z-pack, could cause a potentially fatal irregular heart rhythm in some patients.

The New England Journal of Medicine released results of a study in May 2012 comparing the risks of cardiovascular death from different antibacterial drugs and found that the drug, manufactured by Pfizer Inc. and is also sold by generic drug makers, had a higher rate of death.

In its warning, the FDA said the drug can also cause abnormal changes in the electrical activity of the heart that may lead to a potentially fatal heart rhythm known as prolonged QT interval, in which the timing of the heart’s contractions become irregular.

The FDA said doctors should use caution when prescribing the popular antibiotic to patients known to have this condition or who have certain risk factors. Those who may be at increased risk include people with low levels of potassium or magnesium, a slower than normal heart rate, or people who take certain drugs used to treat abnormal heart rhythms or arrhythmias. The drug could also cause problems in people with torsades de pointes, a specific, rare heart rhythm abnormality.

However, the FDA noted that other drugs in the same class as azithromycin known as macrolides also have the potential for causing QT prolongation, as do non-macrolide antibiotics, such as fluoroquinolones, and doctors need to consider all of these risks when choosing an antibiotic.

Zithromax, Zmax or commonly called “Z-pack” is a popular choice because patients can take fewer doses over a shorter period as compared to most antibiotic regimens, which are taken for ten days. U.S. sales of the drug in 2011 exceeded $450 million, according to IMS Health.

Health care professionals should consider the risk of fatal heart rhythms with azithromycin when considering treatment options for patients who are already at risk for cardiovascular events. The FDA notes that the potential risks of QT prolongation with azithromycin should be placed in appropriate context when choosing an antibacterial drug. Alternative drugs in the macrolide class or non-macrolides such as the fluoroquinolones, also have the potential for QT prolongation or other significant side effects that should be considered when choosing an antibacterial drug.

FDA will update health care professionals and the public with any relevant information that becomes available about azithromycin and the risk of abnormal heart rhythms.

The FDA said it has updated the drug’s labels with information about the risk of QT interval prolongation and torsades de pointes.

“Zithromax has had a well-established benefit risk profile for more than 20 years and continues to be an effective treatment option for patients all over the globe suffering from many types of bacterial infections,” Pfizer said in the statement.

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