Warfarin plus aspirin increases bleeding risk
Adding aspirin to warfarin therapy without a therapeutic indication increased the risk for bleeding and related hospitalization, according to findings published in JAMA Internal Medicine.
“It is not clear how often patients receive aspirin (acetylsalicylic acid) while receiving oral anticoagulation with warfarin sodium without a clear therapeutic indication for aspirin, such as a mechanical heart valve replacement, recent percutaneous coronary intervention, or acute coronary syndrome,” Jordan K. Schaefer, MD, from the University of Michigan, Ann Arbor, and colleagues wrote. “The clinical outcomes of such patients treated with warfarin and aspirin therapy compared with warfarin monotherapy are not well defined to date.”
Schaefer and colleagues conducted a registry-based cohort study to determine how often patients with atrial fibrillation or venous thromboembolism are prescribed aspirin in addition to warfarin without an apparent therapeutic indication, as well as its clinical impact.
At 1, 2 and 3 years, the researchers measured rates of any bleeding, major bleeding events, ED visits, hospitalizations and thrombotic events.
The cohort included 6,539 patients (50.9% men; mean age, 66.1 years). Of those, 37.5% were receiving warfarin and aspirin therapy without a clear indication.
The researchers’ propensity score-matched 3,688 patients, with half receiving warfarin and aspirin and the other half receiving warfarin only.
At 1 year, rates of overall bleeding (cumulative incidence, 26% vs. 20.3%), major bleeding (5.7% vs. 3.3%), ED visits for bleeding (13.3% vs. 9.8%) and hospitalizations for bleeding (8.1% vs. 5.2%) were statistically higher among patients receiving combination warfarin and vs. those receiving warfarin alone.
The two groups demonstrated similar rates of thrombosis at 1 year. The cumulative incidence of thrombosis was 2.3% (95% CI, 1.6-3.1) for those receiving both warfarin and aspirin therapy compared with 2.7% (95% CI, 2-3.6) for those receiving warfarin only.
These findings were consistent during 3 years of follow-up and in sensitivity analyses.
“Similar to other studies published for more than a decade, we did not observe any clinical benefit of aspirin being prescribed with warfarin therapy,” Schaefer and colleagues concluded.
“Unfortunately, the rate of combined warfarin and aspirin use has not declined as a result of those findings, emphasizing the need for greater awareness of this issue and efforts to discontinue aspirin therapy in these patients, especially low-risk patients,” they added. “Further research is needed to help clinicians better stratify which patients should receive combination warfarin and aspirin therapy instead of warfarin monotherapy for venous thromboembolism or atrial fibrillation.” – by Alaina Tedesco
Disclosures: Schaefer reports no relevant financial disclosures. Please see study for all other authors’ relevant financial disclosures.