The U.S. Food and Drug Administration has issued a warning stating that the commonly prescribed antibiotic azithromycin (Zithromax or Zmax) can cause irregular heart activity and result in a fatal heart rhythm.

Zithromax is widely prescribed to treat a series of infections such as pneumonia, bronchitis, wheezing and COPD.

Patients with preexisting heart problems or low blood levels of potassium or magnesium are at a particularly high risk of developing this side effect of the medication.

The FDA says that doctors should be aware of the risk of fatal heart rhythm associated with azithromycin and consider prescribing alternative antibiotics among their patients with existing heart conditions or low blood-potassium/magnesium levels.

Some other alternative drugs such as fluoroquinolones also increase the risk of QT prolongation.

A revised Warnings and Precautions box on the label of azithromycin will include information about the increased risk of QT interval prolongation and Torsades de Pointes - a rare heart rhythm problem.

The new warning comes following review of a study published in the New England Journal of Medicine conducted by researchers at Vanderbilt University. The study revealed that patients who took the antibiotic were at a higher risk of developing heart problems.

Researchers looked at the health risks of several different antibiotics (azithromycin, amoxicillin, ciprofloxacin ,and levofloxacin) by gathering data from over 540 million prescriptions made between 1992 to 2006. Of all the antibiotics prescribed, Zithromaz was found to cause the most heart problems.

According to the FDA statement:

"The study reported an increase in cardiovascular deaths, and in the risk of death from any cause, in persons treated with a 5-day course of azithromycin (Zithromax) compared to persons treated with amoxicillin, ciprofloxacin, or no drug. The risks of cardiovascular death associated with levofloxacin treatment were similar to those associated with azithromycin treatment."

Azithromycin is currently prescribed for the following conditions:
  • Acute bacterial exacerbations of chronic pulmonary disease
  • Acute bacterial sinusitis
  • Community-acquired pneumonia
  • Pharyngitis/tonsillitis
  • Uncomplicated skin and skin structure infections
  • Urethritis and cervicitis
  • Genital ulcer disease


Written by Joseph Nordqvist