Drug interactions
aspirin + warfarin
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Overview
Additive antithrombotic effects markedly increase bleeding risk (GI, intracranial). High-dose salicylates may also raise INR. Combination should be avoided unless a strong indication exists.
Mechanism of action
Pharmacodynamic: platelet inhibition plus anticoagulation and GI mucosal injury → bleeding. Pharmacokinetic: high-dose salicylates may displace warfarin/prolong INR.
Clinical management
Avoid routine coadministration. If required (e.g., mechanical valve, recent ACS), use low-dose aspirin (≤100 mg/day), consider PPI for GI protection, increase INR and CBC/hemoglobin monitoring, counsel on bleeding, avoid other NSAIDs/antithrombotics.
Drug reference
References
- Coumadin (warfarin sodium) Prescribing Information — FDA Label
- Warfarin: Drug Interactions — Lexicomp
- Warfarin and aspirin Interactions — Drugs.com
Frequently asked questions
Can I take aspirin with warfarin?
The interaction is rated: Major. Additive antithrombotic effects markedly increase bleeding risk (GI, intracranial). High-dose salicylates may also raise INR. Combination should be avoided unless a strong indication exists.
How serious is the interaction between aspirin and warfarin?
The interaction is rated: Major. Evidence level: High.
How is the interaction between aspirin and warfarin managed?
Avoid routine coadministration. If required (e.g., mechanical valve, recent ACS), use low-dose aspirin (≤100 mg/day), consider PPI for GI protection, increase INR and CBC/hemoglobin monitoring, counsel on bleeding, avoid other NSAIDs/antithrombotics.
Why do aspirin and warfarin interact?
Pharmacodynamic: platelet inhibition plus anticoagulation and GI mucosal injury → bleeding. Pharmacokinetic: high-dose salicylates may displace warfarin/prolong INR.
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