May 18, 2012 — A study published in the New England Journal of Medicine has linked the 5-day course of the popular antibiotic Zithromax (azithromycin) to a higher risk of cardiovascular death, compared to people treated with amoxicillin, ciprofloxacin, or no drug. In response, the FDA has issued a notice to doctors and the public. Although the increased risk of death is small, researchers are advising doctors to consider prescribing other antibiotic treatments to patients who have a high risk of death from cardiovascular disorders.
Azithromycin is one of the most widely-prescribed antibiotics in the United States. The popular “Z-pack” is a 5-day regimen, which is more convenient than the 10-day regimen with most other antibiotics. It is prescribed to people who have bacterial infections, such as bronchitis, pneumonia, sore throats, and earaches. In 2011, doctors wrote 55.3 million prescriptions for the drug, and global sales exceeded $1.8 billion.
The researchers analyzed data on more than 540,000 people in Tennessee between the ages of 30-74, from 1992 to 2006. The researchers looked for cardiovascular deaths that occurred while a patient was taking an antibiotic (azithromycin, ciprofloxacin, or amoxicillin) compared to comparable periods when the patient was not taking a drug.
The researchers found that azithromycin was associated with an excess 64.6 deaths per million courses of treatment, compared with 22 deaths for amoxicillin and 24 deaths during non-treatment periods. People who had a history of cardiovascular disorders were at highest risk of death during azithromycin treatment. These high-risk patients include those with a medical history of heart attack, heart failure, diabetes, and also people who have had heart surgery or a stent placed inside the heart.
Zithromax (azithromycin) belongs to a class of drugs known as macrolides, which may cause irregular heart rhythm in some patients. Risk factors for a sudden, severely irregular heart rhythm include a prolonged QT interval. Zithromax is known to prolong the QT interval, and the FDA updated the warning label to include this information in March 2012. Now, the FDA will be updating the label on Zithromax (azithromycin) and other drugs in its class to warn of the risk of cardiovascular side effects, including the risk of death.