Pfizer's popular 'Z-Pak' carries increased fatal risk for some, FDA says

The "Z-Pak" is a convenient and so a popular antibiotic treatment that doctors prescribe for everything from ear infections to pneumonia. But in case anybody missed it earlier, the FDA wants to make clear that for a small group of people, there is a better than average chance it will mess with their heart rhythms and possibly kill them. 

The FDA on Tuesday said it had strengthened its warning on the risks of taking azithromycin, which is sold by Pfizer ($PFE) as Zithromax and also sold as a generic. The dangers have been noted on labels since March 2012, but the FDA provided more detail after reviewing a study that found the slightly elevated danger, as well as a follow-up study done by Pfizer, The New York Times reported. Those with a greater risk include people who naturally have a slower-than-normal heart rate or those being treated with drugs for arrhythmias, as well as people with low levels of potassium or magnesium. 

In a statement, Pfizer pointed out that the risks were already known and that it is a very small group with the potential for increased risk.

The findings come in the midst of elevated concern in the U.S. about antibiotic use and effectiveness. Many health professionals believe antibiotics are overprescribed, leading to resistance. That has brought along it own dangers because some infections can no longer be treated with common drugs, making them more lethal. About 40 million people in the U.S. were prescribed the popular 5-day Z-Pak treatment in 2011. According to IMS Health, azithromycin generated sales that year of $450 million, Reuters reported. 

Last year's study found that the risk of experiencing an irregular heart rhythm when taking azithromycin is higher than for patients who took antibiotics such as amoxicillin and ciprofloxacin. According to The New York Times, it was already known that two related antibiotics, erythromycin and clarithromycin, carried a higher chance of death, but it was previously believed that azithromycin did not.  

- here's the FDA notice
- read the New York Times story
- get more from WSJ (sub. req.)
- here's the Reuters story