Warning on irregular heart rhythms with azithromycin

Azithromycin (Zithromax or Zmax) can cause abnormal changes in the electrical activity of the heart that may lead to a potentially fatal irregular heart rhythm, the FDA warned last week.

The warning was based on an FDA review of a study released last spring, which found higher risk of cardiovascular death in patients on azithromycin therapy compared to those taking no antibiotics, as well as new data from the manufacturer. Patients at particular risk for these adverse effects include those with known risk factors such as existing QT interval prolongation, low blood levels of potassium or magnesium, a slower-than-normal heart rate, or use of certain drugs used to treat arrhythmias.

The FDA recommends that clinicians consider the risk of torsades de pointes and fatal heart rhythms with azithromycin when choosing treatments for patients who are already at risk for cardiovascular events. The potential risk 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, according to an agency press release.