If you’re already taking one blood thinner, mounting research suggests you might not need to take a second one – in fact, found a Michigan Medicine study, when patients on a commonly prescribed blood thinner stop taking aspirin, their risk of bleeding complications drops significantly.
Researchers analysed more than 6 700 people treated at anticoagulation clinics across Michigan, US, for venous thromboembolism, or blood clots, as well as atrial fibrillation, an irregular heart rhythm that can cause stroke. Patients were treated with the common blood thinner warfarin but also took aspirin, despite not having history of heart disease.
“We know that aspirin is not a panacea drug as it was once thought to be and can, in fact, lead to more bleeding events in some of these patients, so we worked with the clinics to reduce aspirin use among patients for whom it might not be necessary,” said Dr Geoffrey Barnes, senior author of the study and a cardiologist at the University of Michigan Health Frankel Cardiovascular Centre.
Over the course of the study intervention, aspirin use among patients decreased by 46.6%. With aspirin used less commonly, the risk of a bleeding complication dropped by 32.3% – amounting to one major bleeding event prevented per every 1 000 patients who stop taking aspirin. The results were published in JAMA Network Open.
‘When we started this study, there was already an effort by doctors to reduce aspirin use, and our findings show that accelerating that reduction prevents serious bleeding complications which, in turn, can be lifesaving for patients,” said Barnes, who is also an associate professor of internal medicine at University of Michigan Medical School. “It’s really important for physicians and health systems to be more cognisant about when patients on a blood thinner should and should not be using aspirin.”
This de-escalation of aspirin use is based on several studies that found concerning links between concurrent aspirin use and different blood thinners.
One study reported that patients taking warfarin and aspirin for atrial fibrillation and VTE experienced more major bleeding events and had more ER visits for bleeding than those taking warfarin alone. Similar results occurred for patients taking aspirin and direct oral anticoagulants – who were found more likely to have a bleeding event but not less likely to have a blood clot.
“While aspirin is an incredibly important medicine, it has a less widely used role than it did a decade ago,” Barnes said. “But with each study, we are seeing far fewer cases in which patients who are already on an anticoagulant are seeing benefit by adding aspirin on top of that treatment. The blood thinner they are taking is already providing some protection from clots forming.”
For some people, aspirin can be lifesaving. Many patients who have a history of ischaemic stroke, heart attack or a stent placed in the heart to improve blood flow – as well as those with a history of cardiovascular disease – benefit from the medication.
The challenge comes when some people take aspirin without a history of cardiovascular disease and are also prescribed an anticoagulant, said first author Dr Jordan Schaefer, a haematologist at U-M Health and clinical associate professor of internal medicine at U-M Medical School.
“Many of these people were probably taking aspirin for primary prevention of heart attack or stroke, which we now know is less effective than once believed, and no one took them off it when they started warfarin,” Schaefer said. “These findings show how important it is to only take aspirin under the direction of your doctor and not to start taking over-the-counter medicines like aspirin until you review with your care team if the expected benefit outweighs the risk.”
Study details
Assessment of an Intervention to Reduce Aspirin Prescribing for Patients Receiving Warfarin for Anticoagulation.
Jordan Schaefer, Josh Errickson, Xiaokui Gu, Tina Alexandris-Souphis, Mona Ali, Brian Haymart, Scott Kaatz, Eva Kline-Rogers, Jay Kozlowski, Gregory Krol, Vinay Shah, Suman Sood, James Froehlich, Geoffrey Barnes.
Published in JAMA Network Open on 19 September 2022.
Key Points
Question Is it possible to reduce excess aspirin (acetylsalicylic acid) use among patients treated with warfarin, and is reducing excess aspirin use associated with improved clinical outcomes?
Findings This multicentre quality improvement study of 6 738 adults taking warfarin for atrial fibrillation and/or venous thromboembolism without an apparent indication for concomitant aspirin found that an anticoagulation clinic–based aspirin deimplementation intervention was associated with a significant acceleration of a preexisting decrease in excess aspirin use. Reducing aspirin use was associated with significantly less bleeding and healthcare use; no increase in thrombotic outcomes was observed.
Meaning This study suggests it is possible to reduce aspirin use without a clear indication and that this effort may be associated with improved clinical outcomes.
Abstract
Importance
For some patients receiving warfarin, adding aspirin (acetylsalicylic acid) increases bleeding risk with unclear treatment benefit. Reducing excess aspirin use could be associated with improved clinical outcomes.
Objective
To assess changes in aspirin use, bleeding, and thrombosis event rates among patients treated with warfarin.
Design, Setting, and Participants
This pre-post observational quality improvement study was conducted from 1 January 2010 to 31 December 2019, at a six-centre quality improvement collaborative in Michigan among 6 738 adults taking warfarin for atrial fibrillation and/or venous thromboembolism without an apparent indication for concomitant aspirin. Statistical analysis was conducted from 26 November 2020, to 14 June 2021.
Intervention
Primary care professionals for patients taking aspirin were asked whether an ongoing combination aspirin and warfarin treatment was indicated. If not, then aspirin was discontinued with the approval of the managing clinician.
Main Outcomes and Measures
Outcomes were assessed before and after intervention for the primary analysis and before and after 24 months before the intervention (when rates of aspirin use first began to decrease) for the secondary analysis. Outcomes included the rate of aspirin use, bleeding, and thrombotic outcomes. An interrupted time series analysis assessed cumulative monthly event rates over time.
Results
A total of 6 738 patients treated with warfarin (3 160 men [46.9%]; mean [SD] age, 62.8 [16.2] years) were followed up for a median of 6.7 months (IQR, 3.2-19.3 months). Aspirin use decreased slightly from a baseline mean use of 29.4% (95% CI, 28.9%-29.9%) to 27.1% (95% CI, 26.1%-28.0%) during the 24 months before the intervention (P < .001 for slope before and after 24 months before the intervention) with an accelerated decrease after the intervention (mean aspirin use, 15.7%; 95% CI, 14.8%-16.8%; P = .001 for slope before and after intervention). In the primary analysis, the intervention was associated with a significant decrease in major bleeding events per month (preintervention, 0.31%; 95% CI, 0.27%-0.34%; postintervention, 0.21%; 95% CI, 0.14%-0.28%; P = .03 for difference in slope before and after intervention). No change was observed in mean percentage of patients having a thrombotic event from before to after the intervention (0.21% vs 0.24%; P = .34 for difference in slope). In the secondary analysis, reducing aspirin use (starting 24 months before the intervention) was associated with decreases in mean percentage of patients having any bleeding event (2.3% vs 1.5%; P = .02 for change in slope before and after 24 months before the intervention), mean percentage of patients having a major bleeding event (0.31% vs 0.25%; P = .001 for change in slope before and after 24 months before the intervention), and mean percentage of patients with an emergency department visit for bleeding (0.99% vs 0.67%; P = .04 for change in slope before and after 24 months before the intervention), with no change in mean percentage of patients with a thrombotic event (0.20% vs 0.23%; P = .36 for change in slope before and after 24 months before the intervention).
Conclusions and Relevance
This quality improvement intervention was associated with an acceleration of a pre-existing decrease in aspirin use among patients taking warfarin for atrial fibrillation and/or venous thromboembolism without a clear indication for aspirin therapy. Reductions in aspirin use were associated with reduced bleeding. This study suggests that an anticoagulation clinic–based aspirin deimplementation intervention can improve guideline-concordant aspirin use.
See more from MedicalBrief archives:
Major bleeding risk with warfarin and aspirin together
Aspirin not increasing heart failure events in heart failure patients – WARCEF trial
Two-medicine regime after stenting safer than current regime