Common antibiotic may increase heart death risk

The use of a common antibiotic is linked to an increased risk of heart deaths, a new study suggests.

Researchers looked at more than five million cases of antibiotic treatment in Danish adults ages 40-74 from 1997 to 2011. They found that people in the study who had been treated with an antibiotic called clarithromycin had a 76 percent higher risk of cardiac death compared with people who had been treated with a type of penicillin.

"For every million courses of clarithromycin there were 37 additional cardiac deaths‎," Dr. Wayne Ray, a professor of health policy at Vanderbilt University, told CBS News.

Clarithromycin is used in the treatment of common bacterial infections, and it belongs to a group of antibiotics called macrolides that can interfere with the electrical activity of the heart muscle and increase the risk of potentially fatal heart rhythm problems.

The researchers decided to assess the risk of cardiac death related to the use of clarithromycin and another macrolide antibiotic called roxithromycin, compared with penicillin V, an antibiotic with no known cardiac risk.

Researchers observed an increased risk of cardiac death only in patients who received clarithromycin, but not those who took roxithromycin.

The results showed "[a] significantly increased cardiac risk with clarithromycin and the relative cardiac safety of roxithromycin," the authors wrote in the study, published Wednesday on the website for The BMJ, formerly known as the British Medical Journal.

However, the investigators also stressed that the absolute increase in risk is small and doctors should not change the way they prescribe this particular antibiotic until the new findings are confirmed.

"Patients with heart problems are the ones who should be most aware of this adverse effect, and for these patients it will become more important in deciding which antibiotic to use," Ray said.