Zithromax, Levaquin Linked to Heart Rhythm Problems: Study

Side effects of the antiobiotics Zithromax and Levaquin may both be linked to an increased risk of heart problems, according to the findings of new research.  

In a study published in the March/April issue of the Annals of Family Medicine, researchers from the University of South Carolina found that the two antibiotics were associated with a statistically significant increased risk of death and cardiac arrhythmia.

The findings appear to confirm previous concerns about the side effects of Zithromax, which is more commonly known as Z-Pak or ZMax, but raises new questions about Levaquin.

Researchers looked at data from the U.S. Veterans Affairs medical centers involving nearly 1.8 million individuals given Zithromax, Levaquin or amoxicillin, which they used as a control. They found that ZMax was typically dispensed for five days, while Levaquin and amoxicillin were prescribed for 10 days on average.

Use of Zithromax was found to carry a significantly increased the risk of mortality and arrhythmia on days 1-5, but did not increase risks on days 6-10, when it was given as a 10 day treatment. Levaquin more than doubled the risk of death and arrhythmia throughout the entire 10 days it was prescribed.

Antibiotic Heart Risks

Zithromax (azithromycin) is a member of a class of antibacterial drugs known as macrolides, which have been known to cause abnormal heart rhythm problems, including QT interval prolongation. These side effects can lead to a fatal heart condition, known as torsades de pointes.

In May 2012, a study published in the New England Journal of Medicine first warned about the potential heart risks. Researchers found patients were 2.5 times more likely to die due to heart related problems on a five day Zithromax treatment when they compared it to treatment with other antibiotics or no antibiotic therapy.

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.