Common heart drug may raise bleeding risk when paired with two blood thinners

Older adults who took the heart medication diltiazem alongside either apixaban or rivaroxaban experienced more serious bleeding than similar patients using metoprolol with the same anticoagulants, according to a large study.

The research was observational and focused on people with atrial fibrillation, a type of irregular heartbeat. It points to a possible drug interaction, but it does not prove that diltiazem by itself caused the higher bleeding rate.

Apixaban and rivaroxaban are anticoagulants, commonly known as blood thinners. They help prevent clots and stroke in people with atrial fibrillation, although bleeding is a known side effect of this treatment.

Diltiazem and metoprolol are both used to control heart rate. Diltiazem is also prescribed for high blood pressure and certain other heart conditions.

In the study, researchers reviewed records for 204,155 U.S. Medicare beneficiaries age 65 and older who had atrial fibrillation and started one of the two anticoagulants. They compared those who also began diltiazem with those who started metoprolol.

Serious bleeding was defined as a hospitalization for bleeding or death with recent evidence of bleeding. The diltiazem group had an estimated 21% higher relative rate of serious bleeding than the metoprolol group.

That translated to about 10.6 additional serious bleeding events per 1,000 person-years of follow-up. Person-years reflect the total time patients were observed, not the share of patients who had a bleed.

The difference was especially clear at diltiazem doses above 120 milligrams per day. Researchers did not find a significant difference between the groups in the combined outcome of stroke or systemic embolism.

The findings were published in JAMA. One possible explanation is that diltiazem may affect how the body handles anticoagulants and raise their levels, though the study did not directly prove that mechanism for individual patients.

Even though the researchers adjusted for many differences between the groups, medical records cannot capture every factor that may influence treatment decisions or bleeding risk. The results apply to the drugs and patient group studied, not to every blood pressure medicine or blood thinner.

The study compared two ways of managing heart rate in patients taking specific anticoagulants. It did not compare people taking diltiazem with people taking no heart-rate medicine.

A higher relative rate describes a difference between groups, not the chance that any one person will bleed. Absolute risk can vary depending on age, dose, other medicines, and overall health.

The results add to the information clinicians can use when weighing treatment combinations. Stopping an anticoagulant or heart medicine without medical advice can create other serious risks.

If you are interested in this topic, please read articles about A heart-healthy diet: tips for managing heart rhythm disorders, and Why coffee may affect your heartbeat.

For more information, please see articles about The Mediterranean diet could protect heart health in people with heart disease, and Omega-3 fatty acids and heart health: What you need to know.

Source: Vanderbilt University Medical Center.