Ann Arbor, MI—Concurrent use of aspirin (ASA) by patients who are also taking a direct oral anticoagulant (DOAC) for atrial fibrillation (AF) and/or venous thromboembolism should be weighed very carefully to make sure the risks don’t outweigh the benefits, according to a new study.

A report in JAMA Internal Medicine notes that, in a registry-based cohort study, a third of patients treated with DOACs were also taking ASA. Yet, those patients on combination therapy had significantly higher rates of bleeding and hospitalizations for bleeding without observed difference in thrombosis rates, study authors advise, after comparing two propensity score–matched groups of 1,047 patients without a history of heart-valve replacement or recent acute coronary syndrome,

University of Michigan–led researchers conclude that many patients using DOAC therapy might be using concomitant ASA, increasing their risk of bleeding without certain therapeutic benefit.

“The combination of ASA with oral anticoagulation can be indicated for patients with certain devices (e.g., left ventricular assist devices) as well as for patients with nonvalvular atrial fibrillation and/or venous thromboembolism (VTE) who experience an acute coronary syndrome (ACS) and/or undergo percutaneous coronary intervention (PCI),” the authors pointed out. “Aside from these situations and select other clinical scenarios, there is evidence that the combination of ASA and an oral anticoagulant may increase bleeding, without a significant reduction in thrombotic outcomes. Recent guidelines recommend against prophylactic ASA use for patients at an increased risk of bleeding with concurrent use of anticoagulants.”

The study took place at four anticoagulation clinics in Michigan from January 2015 to December 2019. Included were adults undergoing treatment with a DOAC for AF or VTE, without a recent myocardial infarction (MI) or history of heart-valve replacement, with at least 3 months of follow-up. In the study cohort of 3,280 patients, 51% men with a mean age of 68 years, 33.8% were using ASA without clear indication along with DOACs.

Researchers were tracking rates of bleeding (any, nonmajor, major), rates of thrombosis (stroke, VTE, MI), emergency-department visits, hospitalizations, and death.

The study team analyzed two propensity score–matched cohorts, each with 1,047 patients; one included patients taking DOACs plus ASA and the other was DOACs only. Patients were followed up for a mean of 20.9 months.

Results indicated that patients taking a DOAC and ASA experienced more bleeding events compared with DOAC monotherapy (26.0 bleeds vs. 31.6 bleeds per 100 patient years, P = .01). Researchers reported that, specifically, patients undergoing combination therapy had significantly higher rates of nonmajor bleeding (26.1 bleeds vs. 21.7 bleeds per 100 patient years, P = .02) compared with DOAC monotherapy.

On the other hand, major bleeding rates were found to be similar between the two cohorts, as were thrombotic event rates (2.5 events vs. 2.3 events per 100 patient years for patients treated with DOAC and ASA compared with DOAC monotherapy, P = .80).

Still, patients were more often hospitalized while undergoing combination therapy (9.1 vs. 6.5 admissions per 100 patient years, P = .02), the authors emphasized.

Researchers called for future research to identify and deprescribe ASA for patients when the risk exceeds the anticipated benefit, adding, “With hundreds of thousands of patients on combination therapy with an anticoagulant and antiplatelet medication, it is critical to develop a better understanding of which patients treated with oral anticoagulation should also receive ASA.”

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