Many Patients on DOACs Receive Concurrent Nonindicated Aspirin Tied to Bleeding Risk

By Lisa Rapaport

April 23, 2021

(Reuters Health) - Up to about one in three patients on direct oral anticoagulants (DOACs) may receive concurrent treatment with aspirin without a clear indication, exposing them to increased bleeding risk, a recent study suggests.

Researchers examined data on 3,280 patients being treated with a DOAC for atrial fibrillation or venous thromboembolic (VTE) disease who had no recent history of myocardial infarction or history of heart valve replacement. Overall, 1,107 (33.8%) patients who had no clear indication for aspirin therapy were being treated with both aspirin and a DOAC.

After a mean follow-up period of 20.9 months, patients on concurrent aspirin and DOAC therapy had significantly more bleeding events than patients on DOAC monotherapy (31.6 v 26.0 per 100 patient-years, respectively).

"Studies have fairly consistently shown that taking a daily aspirin increases bleeding risk, and this is what we observed in our study of patients taking direct oral anticoagulants for atrial fibrillation and/or VTE, who did not have a clear indication for adding aspirin," said lead study author Dr. Jordan Schaefer, a hematologist at the University of Michigan in Ann Arbor.

When researchers looked at specific types of bleeding events, they found nonmajor bleeding was significantly more common with dual aspirin and DOAC therapy (26.1 events per 100 patient-years) than with DOAC monotherapy (21.7 events per 100-patient years). Major bleeding also appeared more common with dual therapy, but the difference wasn't statistically significant.

Dual therapy with aspirin and a DOAC also wasn't associated with a significant difference in thrombotic outcomes compared with DOAC therapy alone, researchers report in JAMA Internal Medicine.

"This could be because some patients don't really need the aspirin, especially if they do not have significant risk factors for thrombosis," Dr. Schaefer said by email. "However, it is important to note that we did not have very many clotting events in our study."

One limitation of the study is that aspirin use wasn't randomized and was only assessed once at the time of enrollment, the study team notes. Researchers may have also lacked data on nonprescription aspirin utilization in certain cases.

Even so, the results underscore the importance of clinicians doing periodic medication reviews for patients with cardiovascular disease, said Dr. Deborah Siegal of University of Ottawa and the Ottawa Hospital Research Institute in Canada.

"This should be done at regular intervals to confirm an ongoing indication for antithrombotic therapies and that the drug and dose are appropriate the patient's current clinical status and consistent with available evidence," Dr. Siegal, who wasn't involved in the study, said by email.

Clinicians must also keep current with best practices for pharmacological interventions, said Dr. Gregory Piazza, director of vascular medicine at Brigham and Women's Hospital and an associate professor at Harvard Medical School in Boston.

"The medical literature moves quickly and practices that have become tradition, such as primary prevention aspirin, can be proven to be obsolete from one day to the next," Dr. Piazza, who wasn't involved in the study, said by email. "The weight of the evidence and most recent guidelines recommend against primary prevention aspirin because the risk of bleeding outweighs any potential benefit."

SOURCE: JAMA Internal Medicine, online April 19, 2021.