Certain patients at risk for arrhythmias with azithromycin use, FDA warns

The U.S. Food and Drug Administration (FDA) is warning the public that azithromycin  can cause abnormal changes in the electrical activity of the heart that may lead to a potentially fatal irregular heart  rhythm. Patients at particular risk for developing this condition 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.