Three-month antibiotic treatment reduces risk of future heart attack

March 11, 2002

DALLAS, March 12 - An antibiotic prolonged life and reduced risk of future heart attacks in people hospitalized for heart attack or unstable angina, according to a report in today's rapid access issue of Circulation: Journal of the American Heart Association.

The antibiotic clarithromycin significantly lowered risk of death or serious cardiovascular events compared to those given a placebo. Clarithromycin is typically prescribed for respiratory infections.

"Patients with acute heart attacks or severe angina seem to benefit from treatment with a macrolide antibiotic," says lead author Juha Sinisalo, M.D., of Helsinki University Central Hospital in Helsinki, Finland. "The most likely mechanism of action is clarithromycin's antibacterial effect."

Infections are one cause of inflammation, and inflammation plays an important role in the development of coronary heart disease. Increasing evidence from animal and human studies indicates that several infections such as Chlamydia pneumoniae are associated with coronary heart disease.

Although the apparent advantage of clarithromycin likely stems from its antibacterial power, the drug may do double duty in coronary heart disease patients. Clarithromycin also has an anti-inflammatory action that is independent of its effect on bacteria, he says.

"There are only two ways to prove the connection between infections and coronary artery disease: vaccinations and antibiotic therapy," says Sinisalo. "Vaccinations to prevent heart disease are not available. Therefore, we conducted this study to find out if suppressing infections would decrease the rate of new heart attacks."

Researchers have published results from only a few studies that have tested antibiotics for patients with a high risk of heart attack. Trials in patients with stable heart disease have yielded differing results. In a previous randomized study, a macrolide antibiotic was used for one month to treat people with acute coronary problems. The antibiotic seemed to show some benefit when compared to a placebo, but that advantage disappeared within six months.

Sinisalo and his colleagues studied 148 patients, ages 18 to 80, who were admitted to nine hospitals in different parts of Finland between September 1998 and December 2000. These patients had either a serious heart attack or severe chest pain.

The team randomized 74 patients to receive the antibiotic and 74 to get a placebo. Each participant received one 500 milligram tablet of clarithromycin or an identical-looking placebo daily for 85 days. Neither the patients nor the researchers knew who was receiving the drug or the placebo.

Age, gender and cardiovascular risk factors were similar for both groups. There was also no significant difference between the two groups in the use of antibiotics during the study other than the one used in the trial.

During the three-month treatment, 11 of the antibiotic patients and 19 of the placebo patients died or suffered a nonfatal heart attack or unstable angina. Although these findings show a benefit to patients receiving clarithromycin, the difference between the two groups was not statistically significant.

Sinisalo says one reason for that result is that the number of patients in the trial was too small to show a significant benefit at only three months. The patients were followed for an average of 555 days after hospitalization, with follow-up times ranging from 138 to 924 days.

At the end of the study, 16 of the clarithromycin patients and 27 of the placebo patients had died, or suffered a nonfatal heart attack, unstable angina or a stroke. That difference was statistically significant. "The action of clarithromycin seems to be long-lasting," says Sinisalo.

Compared to the placebo group, people in the study who received clarithromycin had a 41 percent lower risk of myocardial infarction or of suffering another serious cardiovascular problem.

Although the results are encouraging, "this study must be interpreted with caution because of the small number of patients," he says.
Co-authors are Kimmo Mattila, M.D.; Ville Valtonen, M.D.; Olli Anttonen, M.D.; Jukka Juvonen, M.D.; John Melin, M.D.; Helena Vuorinen-Markkola, M.D.; and Markku S. Nieminen, M.D.

NR02 - 1034 (Circ/RAP/Sinisalo)

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