Researchers are warning against overuse of macrolides after their analysis found clarithromycin was associated with an increased risk of myocardial infarction, arrhythmia, and cardiac mortality.

The analysis of cardiac events in almost 110,000 patients taking clarithromycin found it was associated with 1.9 extra myocardial infarctions 0.95 extra cardiac deaths and 0.2 extra arrhythmias for every 1000 patients treated compared to amoxycillin.

The study involving patients taking the macrolide for Helicobacter pylori eradication showed an almost fourfold higher risk with clarithromycin compared with amoxycillin in the 14 days after starting antibiotic treatment.

However the risk returned to zero after the drug was stopped and there were no long-term effects, reported the study authors in the BMJ.

The findings added to growing literature showing that the risks of macrolides were “not negligible” said epidemiologists at the Johns Hopkins Bloomberg School of Public Health in Baltimore US in an accompanying editorial.

“Given that as many as a quarter to half of all antibiotics prescribed are not clinically indicated, the opportunities to use these products more judiciously without compromising quality of care are manifold.

“Clinicians and patients should consider these potentially serious adverse events when prescribing macrolides, especially to those at highest baseline risk,” they advised.