Cardiovascular diseases still remain the biggest killer in Europe / Rex Features

More research urgently needed, scientists say

One of the most commonly prescribed antibiotics has been linked with an increased risk of death from heart disease, researchers have said.

Clarithromycin, which is used in the treatment of many bacterial infections, is given to millions of people every year. Its use is already discouraged in patients with certain heart conditions, but in a new analysis of patient data carried out by Danish researchers, the drug was found to cause 37 potentially avoidable deaths compared to similar antibiotics for every one million courses of the antibiotic prescribed.

Although this level of risk is small, they said that the fact that clarithromycin is prescribed to so many people meant that “urgent confirmation” of their findings was required. However, they did not recommend any immediate changes to prescribing practice.

Clarithromycin belongs to a group of antibiotics known as macrolides. These antibiotics are known to affect the rhythm of the heart muscle’s electrical activity – known as the QT interval – and are therefore thought to increase the risk of potentially fatal heart rhythm problems.

Doctors already know to exercise caution when prescribing the drugs to patients with a rare condition called Long QT syndrome, which causes episodes of rapid heart rhythm, or arrhythmia.

However, the new findings, if confirmed in separate studies, could lead doctors to take further precautions. Last year, clarithromycin was prescribed 2.2m times in England, according to the Health and Social Care Information Centre.

The Danish researchers, from the Statens Serum Institut in Copenhagen, analysed more than five million patients treated with three different antibiotics to determine the differing risks of each. Individuals with serious disease were excluded from the analysis.

They said that because the absolute risk was so small, it was unlikely that prescribing practice would have to change. However, they said “clarithromycin is one of the more commonly used antibiotics in many countries and many millions of people are prescribed this drug each year; thus, the total number of excess cardiac deaths may not be negligible”.

After adjusting for factors such as age, sex, cardiac risk and use of other medication, ongoing use of clarithromycin was associated with a 76 per cent higher risk of death from heart disease compared with use of penicillin V – a similar antibiotic. The study was published in the British Medical Journal  today.

Mike Knapton, associate medical director at the British Heart Foundation, said: “All medications can come with side effects, which is why your doctor will always weigh up the risks before prescribing drugs to patients.

“Health professionals already know to exercise caution when prescribing clarithromycin in patients who have, or may be predisposed to Long QT syndrome - a condition that can cause sudden cardiac death. This study shows that they should continue to follow that advice.

“More research is now needed to understand the effect of this antibiotic on the wider population. The bottom line is no one should be taking antibiotics unless they absolutely have to and doctors should give careful consideration before prescribing them. If you are taking clarithromycin at the moment, you should not stop without discussing this further with your GP.”

The authors of the study said that “confirmation in independent populations is an urgent priority given the widespread use of macrolide antibiotics”.