The U.S. Food and Drug Administration issued a new warning for the antibiotic “azithromycin,” more commonly known as Zithromax or Z-Pak. The potential harm is that it interferes with normal heart electrical activity and may cause fatal heart rhythms. This risk is especially high for elderly patients and those with pre-existing heart conditions. Pfizer, the manufacturer of this particular antibiotic, has issued updated warnings on the drug label, but insists that the product is safe and FDA approved. A recent study showing the increase in cardiovascular deaths related to Zithromax prompted the new FDA warning. The FDA also warns that alternatives to this drug may pose serious risks as well, and that an antibiotic should only be taken when necessary, as decided by a physician.