Plenty of us either know someone or are that person who runs to the doctor to get a prescription for the antibiotic Zithromax (azithromycin) to combat anything from bronchitis to pneumonia. The Z-Pak is a common choice for the ill, as it is taken for fewer days than other meds. But the Food and Drug Administration says it’s adding a new warning label to Zithromax due to a risk for rare but deadly heart rhythms in some patients.

The FDA announced yesterday that it’s telling doctors and patients that Pfizer’s popular antibiotic — prescribed to 40 million people in 2011 — could be troublesome for some who take it, especially if they’re already at a risk for heart issues, reports the Associated Press.

Instead, the agency says, doctors should think about prescribing other antibiotics to any patients with existing heart problems like irregular heartbeats or low levels of potassium or magnesium in their blood. Zithromax also comes in generic form as well.

The new label comes after a Vanderbilt University study released last May that showed a slightly higher chance for deadly heart problems for patients taking Zithromax. The results indicated that there could be about 47 extra heart-related deaths per million courses of treatment than there would be for the same amount of amoxicillin courses.

The downside for users who don’t like being on meds for long is that taking amoxicillin or other antibiotics involves a 10 day commitment, as opposed to Z-Pak’s five or so days.

But then again, the other potential downside (ahem, death) could be a lot worse than having to take antibiotics for a few days longer.

FDA adds heart risk warning to Z-Pak [Associated Press]

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