Clarithromycin – a friend or foe in treating coronary heart disease?

This study investigated the safety of the drug, clarithromycin, in treating stable coronary heart disease.

Coronary heart disease, also known as coronary artery disease, is the narrowing or blockage of the coronary arteries that provide the heart with blood that it needs to function and survive.

Coronary arteries can become blocked due to atherosclerosis. This is the build up of cholesterol and fatty deposits (called plaques). These plaques can reduce the blood flow to the heart muscle, starving the heart of oxygen (called ischemia). This can cause chest pain called angina or result in a heart attack if the blood supply to a part of the heart is cut off completely. A patient with coronary heart disease is likely to experience ischemia when the heart demands extra oxygen, such as during physical activity, eating, excitement or stress.

Stable coronary heart disease is when ischemia can be resolved with rest or medication in less than 10 minutes. Unstable coronary artery disease occurs when a patient suffers from ischemia or angina at rest.

Treatment for stable coronary heart disease includes statin drugs, such as simvastatin (Zocor) or antibiotics, such as clarithromycin (Biaxin), which reduce atherosclerosis. However, clarithromycin was previously studied in a group of patients and was associated with a 27% increase in mortality after 2.6 years and 20% after 6 years. The reason behind this harmful effect of clarithromycin is unknown.

This study investigated the long-term effects and safety of clarithromycin (Biaxin) after 10 years.

A total of 4,373 patients with stable coronary heart disease were included in the study. Patients were either given 500 mg a day of clarithromycin or a placebo for 2 weeks. Patients were then followed up 10 years later.

The study found that clarithromycin increased the risk of death by 10%, compared to placebo, and patients who had taken clarithromycin were 19% more likely to die from cerebrovascular disease (disorders in which the circulation to the brain is disrupted).

However, the increased mortality seemed to only occur in patients who were not taking statins at the beginning of the study and seemed to be due to sudden cardiovascular death (sudden, unexpected death caused by loss of heart function). In this group of patients, clarithromycin was associated with a 2.3 fold (230%) increased the risk of death. 

The study concluded that clarithromycin increased the risk sudden cardiovascular death in stable coronary heart disease patients who were not taking statins at the beginning of the trial.

One draw back to the study is that patients who were already taking statin treatment were likely to stay on the treatment and patients not on statins were not likely to get start statin treatment. Therefore, the lower mortality rate in patients taking statins, compared to those who were not taking statins, may be due to the statin drug itself working to treat atherosclerosis and not because statins protect against clarithromycin.

If you or someone you know have coronary heart disease, talk to doctor about what treatments are safe and effective.