A wrod of warning for some. http://vitals.nbcnews.com/_news/201...e-fatal-irregular-heart-rhythm-fda-warns?lite The FDA said doctors should use caution when giving the popular antibiotic to patients known to have this condition or who have certain risk factors. Those who may be at risk include people with low levels of potassium or magnesium, a slower than normal heart rate, or people who take certain drugs used to treat abnormal heart rhythms, or arrhythmias. The drug could also cause problems in people with torsades de pointes, a specific, rare heart rhythm abnormality. However, the FDA noted that other drugs in the same class as azithromycin known as macrolides also have the potential for causing QT prolongation, as do non-macrolide antibiotics, such as fluoroquinolones, and doctors need to consider all of these risks when choosing an antibiotic.