Aspirin is an antiplatelet agent that binds irreversibly to COX-1 and COX-2 enzymes, which results in decreased prostaglandin and thromboxane A2 production and inhibition of platelet aggregation. Aspirin often is used for its antipyretic, analgesic, and antiplatelet properties. Its use in cardiovascular disease (CVD) has been studied extensively over the past few decades, and recent data are changing the framework for aspirin use in primary prevention of atherosclerotic cardiovascular disease (ASCVD). Primary prevention refers to efforts to prevent the incidence of cardiovascular events, whereas secondary prevention refers to efforts to prevent a cardiovascular event after one has occurred.1 This differentiation is important as it guides the course of treatment.
Three trials published in 2018 evaluated aspirin use in primary prevention of ASCVD. The ASCEND trial evaluated aspirin use for primary prevention of ASCVD in patients with diabetes mellitus (DM). This study concluded that although aspirin prevented serious vascular events in patients with DM, the benefit observed was largely counteracted by the bleeding hazard.2 The ARRIVE trial evaluated aspirin use for primary prevention in patients with a moderate CVD risk. The study concluded that aspirin use in patients at moderate risk of CVD could not be assessed due to the low incidence rate of CVD; however, the study concluded that aspirin did not reduce the incidence of cardiovascular events for patients at low CVD risk and that aspirin caused more mild gastrointestinal bleeds compared with placebo.3 The ASPREE trial evaluated aspirin use for primary prevention in patients aged > 70 years to determine whether its use prolonged a healthy lifespan. This trial concluded that patients who received daily aspirin were at a higher risk of major hemorrhage and that aspirin did not diminish CVD risk compared with placebo.4
These studies led to a paradigm shift in therapy to reevaluate aspirin use for primary prevention. Current indications for aspirin include secondary prevention of ASCVD (ie, myocardial infarction [MI], coronary artery bypass graft, transient ischemic attack [TIA], and stroke), venous thromboembolism prophylaxis in the setting of orthopedic surgery, or valvular disease with replacement and analgesia. It is important to note that certain clinical circumstances may warrant aspirin use for primary prevention of ASCVD on a patient-specific basis, and this decision should be made using a risk/benefit analysis with the patient.
In April 2022, the US Preventive Services Task Force (USPSTF) recommended against using low-dose aspirin for primary prevention of ASCVD in individuals aged ≥ 60 years. The USPSTF noted that for patients who have a ≥ 10%, 10-year CVD risk, the decision to initiate aspirin should be based on a risk/benefit discussion and may be beneficial in certain patient populations.5A 2019 National Heart, Lung, and Blood Institute survey found that 29 million Americans used aspirin for primary prevention of ASCVD, and 6.6 million of these Americans used aspirin for primary prevention without the recommendation of a health care professional (HCP). Almost half of these individuals were aged > 70 years and, therefore, at an increased risk for bleeding.6 With the recent studies and changes in guidelines highlighting a higher risk rather than benefit with the use of aspirin for primary prevention, the current use of aspirin for primary prevention in the United States needs to be readdressed.
HCPs should assess the appropriateness of aspirin use in their patients to ensure that the risks of aspirin do not outweigh the benefits. Pharmacists can play a vital role in the assessment of aspirin for primary prevention during patient visits and make recommendations to primary care practitioners to deprescribe aspirin when appropriate.