The antibiotic erythromycin can cause a certain kind of heart problem. Researchers at Vanderbilt University and the Nashville Veterans Affairs Medical Center looked at whether it could kill you.

What the researchers wanted to know: Does taking oral erythromycin increase the risk of sudden cardiac death? What if it's combined with other drugs?

What they did: The researchers studied Medicaid enrollees in Tennessee. They were looking at what medications each person took and whether they died a sudden cardiac death—which is dying suddenly because your heart stops working. Besides erythromycin (and, for comparison, the antibiotic amoxycillin), they were interested in drugs that are known to inhibit so-called CYP3A isozymes, which metabolize erythromycin. A patient who's taking CYP3A inhibitors will have more erythromycin than usual in their blood, since they can't metabolize it as well. Those drugs include some calcium-channel blockers, some antidepressants, and some antifungal drugs.

What they found: People taking erythromycin were twice as likely to die a sudden cardiac death than people who weren't using any of the antibiotics the researchers looked at. The risk of sudden cardiac death was even higher for patients who were taking both erythromycin and one of the CYP3A-inhibiting drugs.

What the study means to you: It looks likes a good idea to avoid mixing erythromycin with drugs that are known to inhibit CYP3A—check with your doctor. The risk was only while patients were taking erythromycin; there was no evidence for an increased risk after they'd finished taking the drug.

Caveats: As always, when you're looking at the risk for a very rare event like sudden cardiac death, you aren't going to see very many of the event even if you start with a really big group of people. In this study, only three people who were taking erythromycin and a CYP3A inhibitor died suddenly of cardiac causes. But the risk is still statistically significant, meaning that those three deaths probably aren't a coincidence.

Find out more: Information on erythromycin from the National Library of Medicine's MedlinePlus.

Read the article: Ray, W.A. et al. "Oral Erythromycin and the Risk of Sudden Death from Cardiac Causes." New England Journal of Medicine. Sept. 9, 2004, Vol. 351, No. 11, pp. 1089–1096.