Azithromycin, often marketed as Zithromax, or Z-Pak is an antibiotic taken by over 60 million people in the U.S. every year. Wednesday the FDA issued a warning on the possible deadly side-effects of the popular antibiotic.
The warning is the result of a study done by the New England Journal of Medicine last May. The results of the study suggested that there would be 47 heart-related deaths per one million courses of treatment with Azithromycin, compared with another antibiotic, amoxicillin.
A usual treatment course for Azithromycin is about five days, where as for amoxicillin it takes an estimated 10 days for full treatment.
The FDA warns that the antibiotic can cause changes in the heart's electrical activity and could lead to a fatal heart arrhythmia.
Patients with known risk factors such as people with existing QT interval prolongation, existing low blood levels of potassium or magnesium, a slower than normal heart rate, or those who use certain drugs to treat abnormal heart rhythms.
The elderly also face an increased risk of a fatal heart arrhythmia because they so often are prescribed multiple medications, some having an unwanted affect on the heart rate.
Pfizer, the maker of Zithromax, said the sale of the drug last year generated $453 million for the pharmaceutical company.