The FDA is warning the public that the pills can cause abnormal changes in the heart’s electrical activity that may lead to a fatal heart rhythm. Not everyone is at risk. Patients with known risk factors such as existing QT interval prolongation, low blood levels of potassium or magnesium, a slower than normal heart rate, or those who use  certain drugs to treat abnormal heart rhythms, or arrhythmias face the greatest risk.

“Health care professionals should consider the risk…