Popular Antibiotic May Be Responsible For Sudden Cardiac Death

Lawrence LeBlond for RedOrbit.com

Azithromycin, a common antibiotic used for treatment of bronchitis, pneumonia, and sexually transmitted diseases (STDs), appears to also boost the risk of sudden cardiac death when compared with no antibiotic treatment, according to a US study on Wednesday.

Azithromycin has been available worldwide since the 1980s, but the new study, published in the New England Journal of Medicine (New England Journal of Medicine), is the first to document serious heart risks with the use of the popular antibiotic.

Researchers at Vanderbilt University compared about 348,000 prescriptions of azithromycin to millions of records from people who were not treated with any antibiotics or who received the common antibiotic amoxicillin, which is considered heart safe.

Compared with no antibiotic treatment, the hazard ratio for cardiovascular death during a 5-day course of azithromycin was 2.88, according to Wayne A. Ray, PhD, of Vanderbilt University in Nashville, and colleagues. And when compared to amoxicillin, azithromycin showed a 2.49 hazard ratio.

The comparisons were made based on patient records in Tennessee from 1992 to 2006.

The analysis found 47 more deaths per million in those taking azithromycin compared to those taking amoxicillin. When the researchers examined patients already at high risk for heart problems, the chance increased to 245 more deaths per million in the azithromycin group compared to the amoxicillin group.

While the increased odds of death are small, the researchers note they are significant enough to get the attention of medical experts and also urge them to consider prescribing a different drug to those patients who are already at high risk of heart problems.

People at high risk include those with heart failure, diabetes or who have had a previous heart attack, and for those who have undergone bypass surgery or have had stents implanted. In such patients, the drug may cause fatal abnormal heart rhythms.

Ray said the concerns should not apply to children as they have very little risk of heart disease.

Azithromycin is commonly used for a number of illnesses, and is most familiarly used as the “Z-Pak,” taken for five days. It is considered a convenient treatment option because most other antibiotics need to be taken for at least 10 days.

More than 55.3 million prescriptions for azithromycin were written last year in the US, and sales topped $464 million, according to medical information and services firm IMS Health. Global sales topped $1.8 billion.

“We believe this study adds important information on the risk profile for azithromycin,” Ray told AFP. “For patients with elevated cardiovascular risk and infections for which there are alternative antibiotics, the cardiovascular effects of azithromycin may be an important clinical consideration.”

“I´m inclined to agree with Dr. Ray,” Dr. John G. Bartlett,  professor of medicine at Johns Hopkins University School of Medicine and a former president of the Infectious Diseases Society of America, told the New York Times.

He said the study convinced him because it included data on a huge number of patients and because the findings were biologically plausible, given that related drugs had also been found capable of disrupting heart rhythm.

Bartlett said he would consider prescribing a different drug to patients at high risk. There are plenty of alternatives, he noted.

Bartlett also noted that the study provided another reason to halt the overuse of antibiotics, which are often prescribed to illnesses they cannot treat. Overuse of these antibiotic drugs has contributed to the emergence of dangerous, drug-resistant bacteria strains.

“We use azithromycin for an awful lot of things, and we abuse it terribly,” Bartlett told New York Times writer Denise Grady. “It´s very convenient. Patients love it. ℠Give me the Z-Pak’. For most of where we use it, probably the best option is not to give an antibiotic, quite frankly.”

Dr. Lori Mosca, director of preventive cardiology at New York-Presbyterian Hospital/Columbia University Medical Center, said azithromycin´s benefits may outweigh the small risks suggested by the study.

She noted that the study was observational rather than clinical, meaning the researchers looked back at medical records, rather than setting up experiments in which patients were assigned random treatments and then monitored. Even the most careful observational study can be misleading, Mosca said.

She said a more rigorous study should be done to verify the findings.

“It would be crazy to think we can´t use azithromycin. It´s bad to undertreat infections,” she told Grady

Dr. Roy M. Gulick, the chief of infectious diseases at New York-Presbyterian/Weill Cornell, also said that more research was needed. But, he said: “In someone with significant cardiovascular risks or documented disease, the results of this study would be one factor that would help you choose among the antibiotics.”

“Any antibiotic is going to have risks and benefits,” Ray said. “We think this is an important piece of information about risks.”

The authors acknowledged they had potential difficulties with confounding in the study, relating to various factors such as underlying cardiovascular disease and behavioral risk factors such as smoking and diet. They addressed this by choosing controls that were matched according to propensity scores, they explained.

A second source of potential confounding was the direct effect of infections, but they limited this by having the additional control group of patients being treated with amoxicillin, which is used for similar indications as azithromycin.

Azithromycin is a macrolide antibiotic that works by stopping the growth of bacteria. Side effects may include skin rashes, itching, swelling, difficulty breathing or swallowing and rapid, pounding or irregular heartbeats, according to the American Hospital Formulary Service.

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