Is aspirin (acetylsalicylic acid) 81 mg twice daily (BID) effective for deep vein thrombosis (DVT) prophylaxis?

Aspirin 81 mg BID for DVT Prophylaxis: Efficacy Assessment

Aspirin 81 mg twice daily is not recommended as an effective regimen for deep vein thrombosis (DVT) prophylaxis in most clinical settings, with very limited exceptions. 1

Evidence Against Aspirin for DVT Prophylaxis

• According to the National Comprehensive Cancer Network (NCCN) guidelines, aspirin is not considered to be effective for venous thromboembolism (VTE) prophylaxis in most clinical settings 1
• Aspirin (81-325 mg/d) is only considered an option for VTE prophylaxis in a select group of patients with multiple myeloma who are at low risk for VTE (≤1 individual or multiple myeloma risk factor) 1
• In the Women's Health study, a 10-year study of healthy women randomly assigned to aspirin (100 mg) or placebo on alternate days, no significant differences in the incidence of VTE were observed between the arms 1

Limited Evidence Supporting Aspirin Use

• In orthopedic surgery settings, particularly after total knee arthroplasty (TKA) and total hip arthroplasty (THA), some evidence suggests aspirin may be effective for VTE prophylaxis 2, 3, 4
• A 2018 study found that low-dose aspirin (81 mg BID) was not inferior to high-dose aspirin (325 mg BID) for VTE prevention after TKA 2
• Similarly, a 2019 study showed no difference in symptomatic VTE incidence between low-dose (81 mg BID) and standard-dose (325 mg BID) aspirin after THA 3

Dosing Considerations

• When aspirin is used for cardiovascular indications, the American College of Cardiology/American Heart Association recommends a daily aspirin dose of 81 mg (range 75-100 mg) 1
• There is no established evidence supporting the specific regimen of aspirin 81 mg BID for DVT prophylaxis in general medical patients 1

Special Populations

• In mechanically ventilated ICU patients, one retrospective study suggested aspirin may reduce DVT risk (OR 0.39,95% CI 0.16-0.94), but this is insufficient evidence to recommend routine use 5
• For patients with multiple myeloma at low risk for VTE, aspirin 81-325 mg daily (not twice daily) may be considered 1
• In orthopedic surgery, particularly after joint replacement, aspirin may be an option for extended prophylaxis after initial anticoagulation 4

Preferred Alternatives for DVT Prophylaxis

• Low molecular weight heparins (LMWH) are generally preferred over aspirin for DVT prophylaxis in high-risk patients 1, 6
• For patients who cannot receive anticoagulation, intermittent pneumatic compression (IPC) devices are recommended as they have no associated bleeding risk 1
• For patients with cancer, aspirin cannot be recommended for VTE prophylaxis or extended treatment of VTE 1

Clinical Pitfalls to Avoid

• Do not rely on aspirin as the sole agent for DVT prophylaxis in most hospitalized patients or those with significant VTE risk factors 1
• Avoid assuming that aspirin's cardiovascular benefits automatically translate to effective VTE prevention 1, 6
• Be cautious with aspirin use in patients with acquired von Willebrand disease who have an increased risk of bleeding 1
• Do not use graduated compression stockings alone for DVT prophylaxis, as they have been shown to be ineffective for VTE prevention in certain populations 1

In conclusion, while aspirin 81 mg BID may have limited utility in specific orthopedic settings, it is not broadly recommended for DVT prophylaxis in most clinical scenarios. Standard anticoagulants remain the preferred option for most patients requiring pharmacologic DVT prophylaxis.