Researchers have explained why commonly used antibiotics like clarithromycin can lead to an increased risk of heart attacks, opening up the possibility of precision prescribing based on a patient's genes.

In recent years, it has been suggested that patients taking clarithromycin rather than alternative antibiotics are more likely to suffer a serious cardiovascular event, but research into this association had proved inconclusive. For the results, the research team from the University of Dundee in the UK took a different approach to previous studies. Taking advantage of the extensive electronic database compiled locally, they explored both medical prescribing records and genetic data to determine whether clarithromycin use is indeed linked to an increased risk of heart problems.

Their study showed that compared to patients prescribed amoxicillin, those taking clarithromycin are 31 percent more likely to be admitted to the hospital with a heart problem within 14 days of starting the prescription and 13 percent more likely to be admitted to the hospital with a heart problem up to a year after the conclusion of the prescription. In addition, they found that patients taking certain types of medications, such as statins, at the same time are even more likely to have a heart issue if given clarithromycin rather than amoxicillin.

Medications such as statins and clarithromycin work in the body using a pathway controlled by a protein called P-glycoprotein. Using genetic data, the researchers found that patients with a genetic predisposition to lower P-glycoprotein activity are also at 40 percent higher risk of heart problems up to a year after taking clarithromycin rather than amoxicillin. Taken together, these results suggest that patients should be prescribed alternative antibiotics if they are taking P-glycoprotein inhibitors such as statins, or if they have a particular genotype.

"We set out to examine whether this association might be mediated via P-glycoprotein, a major pathway for clarithromycin metabolism," said study author Ify Mordi from the University of Dundee. "We found that clarithromycin use was associated with an increased risk of cardiovascular hospitalisation up to a year post-prescription compared to amoxicillin," Mordi added.