Popular antibiotic gets cardiac warning

An antibiotic prescribed for a wide variety of infections may pose heart risks, the US Food and Drug Administration has warned. Azithromycin, sold as Zithromax or the "Z-Pak," may cause abnormal changes in the heart's electrical activity, the FDA said. Those changes may lead to a potentially deadly irregular heart rhythm, the agency added. Patients at risk include those with low blood levels of magnesium or potassium and heart rates that are slower than normal, the FDA said. People who take certain drugs for abnormal heart rhythms are at risk as well. Pfizer, which makes Zithromax, updated the drug's label about the rare heart rhythm abnormality in some patients. "It is important to note that other macrolide antibiotics are similarly labeled," the pharmaceutical company said. "It is also important to note that the majority of patients treated with Zithromax (azithromycin) are not affected by this label update." Zithromax is used to treat infections in the ear, lungs, reproductive organs, sinuses, skin and throat. Zithromax can be taken as a tablet or liquid. It may cause side effects, such as abdominal pain, diarrhea, nausea and vomiting