Should a patient at high risk for Deep Vein Thrombosis (DVT) who is already taking aspirin (acetylsalicylic acid) and Plavix (clopidogrel) continue these medications when initiating heparin for DVT prophylaxis?

Should Patients Continue Aspirin and Plavix When Using Heparin for DVT Prophylaxis?

No, patients should suspend both aspirin and Plavix (clopidogrel) when initiating heparin for DVT prophylaxis, as the combination significantly increases major bleeding risk without providing additional benefit. 1, 2

The Evidence Against Combining Antiplatelet Therapy with Anticoagulation

The American Society of Hematology 2020 guidelines provide a conditional recommendation to suspend aspirin when anticoagulation therapy is initiated, based on evidence showing increased bleeding risk. 1 Specifically:

• Combining anticoagulation with aspirin increases major bleeding events by 7 more per 1,000 patients (95% CI: 2 fewer to 21 more) compared to anticoagulation alone. 1

• The combination provides no additional thrombotic protection beyond what anticoagulation alone achieves. 2

• This recommendation applies to both aspirin and dual antiplatelet therapy (aspirin plus clopidogrel), as both agents already provide antithrombotic effects that compound bleeding risk when combined with heparin. 3

Clinical Algorithm for Managing Antiplatelet Therapy During DVT Prophylaxis

Step 1: Assess the Indication for Antiplatelet Therapy

For stable cardiovascular disease (primary or secondary prevention):

• Suspend both aspirin and clopidogrel for the duration of heparin prophylaxis 1, 2
• The anticoagulant provides adequate cardiovascular protection during this period 1

For recent acute coronary syndrome or recent coronary intervention (within weeks):

• This recommendation does NOT apply to these patients 1
• These patients require continued dual antiplatelet therapy despite increased bleeding risk
• Use mechanical DVT prophylaxis (sequential compression devices) as the primary strategy 3
• If pharmacologic prophylaxis is absolutely necessary, accept the increased bleeding risk and monitor closely

Step 2: Implement Alternative DVT Prophylaxis Strategy

For patients on dual antiplatelet therapy who cannot safely suspend medications:

• Use mechanical prophylaxis (intermittent pneumatic compression) as the primary method 3, 4
• Avoid adding pharmacologic anticoagulation unless VTE risk is extremely high and outweighs bleeding risk 3
• The American College of Chest Physicians specifically recommends mechanical methods for patients at high bleeding risk 4

For patients who can suspend antiplatelet therapy:

• Initiate standard heparin prophylaxis (unfractionated heparin 5,000 units subcutaneously every 8-12 hours or LMWH) 4
• Resume antiplatelet therapy only after completing the period requiring DVT prophylaxis 1

Important Distinctions: Prophylaxis vs. Treatment

This guidance applies to DVT prophylaxis. If a patient develops acute DVT requiring therapeutic anticoagulation:

• Therapeutic anticoagulation is mandatory and aspirin/clopidogrel must be suspended 2, 5
• Aspirin has no role in acute DVT treatment and would constitute treatment failure 2, 5
• The bleeding risk is even higher with therapeutic-dose anticoagulation plus antiplatelet agents 1

Common Pitfalls to Avoid

Pitfall #1: Assuming antiplatelet therapy provides adequate DVT prophylaxis

• Antiplatelet agents reduce PE risk by only about one-half, while heparins reduce it by two-thirds 3
• The American College of Chest Physicians explicitly recommends against using aspirin as sole thromboprophylaxis (Grade 1A recommendation) 3, 4

Pitfall #2: Continuing "just aspirin" while holding clopidogrel

• Even aspirin monotherapy increases bleeding risk when combined with anticoagulation 1
• Both agents should be suspended unless there is a recent acute coronary event 1

Pitfall #3: Failing to reassess the indication for antiplatelet therapy

• Many patients are on aspirin for primary prevention without clear indication 1
• Use the initiation of anticoagulation as an opportunity to critically review whether antiplatelet therapy is truly necessary 1

Special Considerations

For patients with drug-eluting stents:

• If within the critical period (3-6 months for sirolimus, 6-12 months for paclitaxel), continue dual antiplatelet therapy and use mechanical prophylaxis 1
• After this critical period, the approach follows standard recommendations above 1

For patients undergoing orthopedic surgery:

• Some orthopedic guidelines suggest aspirin for prophylaxis, but this is controversial and not universally accepted 3
• For patients already on dual antiplatelet therapy undergoing orthopedic procedures, mechanical prophylaxis remains the primary approach 3