Warfarin and Aspirin Rectal: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Warfarin
Aspirin Rectal
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Increased risk of bleeding, prolongation of both bleeding and prothrombin time
Interaction Deep Dive
Concomitant use of warfarin (an anticoagulant) with aspirin (an antiplatelet agent) may increase the risk of bleeding. If coadministration is required, monitor closely3. Use concurrently for the shortest duration possible based on indication, and consider initiating a proton pump inhibitor if clinically appropriate 4. In patients with DVT and/or pulmonary embolism (PE) and stable cardiovascular disease receiving aspirin for cardiovascular risk modification, suspending aspirin for the duration of anticoagulation therapy for DVT and/or PE is suggested (conditional recommendation based on very low certainty in the evidence of effects); however, this suggestion does not apply to patients with a recent acute coronary event or coronary intervention 1.
Why it happens (mechanism)
Additive effects on hemostasis; displacement of warfarin from protein binding sites
Literature reports
2 reports — tap to read
a) In patients receiving warfarin for atrial fibrillation or VTE, treatment with aspirin without a clear therapeutic indication compared with no aspirin significantly increased 1-year cumulative incidence of overall bleeding (26% vs 20.3%), major bleeding (5.7% vs 3.3%), emergency department (ED) visits for bleeding (13.3% vs 9.8%), and hospitalizations for bleeding (8.1% vs 5.2%) in a propensity score-matched study (n=3688, 1844 patients per group); these results persisted for at least 3 years of follow up. There were no significant differences with aspirin versus no aspirin in the 1-year rates of mortality (4.4% vs 3.7%) and thrombosis (2.3% vs 2.7%; ischemic stroke, TIA , VTE, acute coronary syndrome or myocardial infarction, ED visits, hospitalizations for thrombosis); the type of thrombotic event and rate of CNS bleeding were similar between groups. Low-dose aspirin (100 mg or less per day) was used by 84% of patients receiving aspirin 5.
b) In a meta-analysis of six randomized clinical trials, the use of aspirin with warfarin was associated with more than double the frequency of intracranial hemorrhage. The trials included 3874 patients with 31 diagnosed intracranial hemorrhages. The frequency of intracranial hemorrhage was not dependent on the dose of aspirin used or on the range of anticoagulation. These data suggest that even low doses of aspirin should be used cautiously in anticoagulated patients with a high risk of intracranial hemorrhage, such as the elderly 2.
Common questions
Can I take Warfarin and Aspirin Rectal together?
Increased risk of bleeding, prolongation of both bleeding and prothrombin time Always confirm with your pharmacist or prescriber before making any change.
How serious is the Warfarin and Aspirin Rectal interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "established". Well documented — supported by controlled studies or strong clinical data.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Warfarin or Aspirin Rectal need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (5)
- Ortel TL, Neumann I, Ageno W, et al: American Society of Hematology 2020 guidelines for management of venous thromboembolism: treatment of deep vein thrombosis and pulmonary embolism. Blood Adv 2020; 4(19):4693-4738. PubMed
- Hart RG, Benavente O, & Pearce LA: Increased risk of intracranial hemorrhage when aspirin is combined with warfarin: a meta-analysis and hypothesis. Cerebrovasc Dis 1999; 9:215-217. DOI
- Product Information: WARFARIN SODIUM oral tablets, warfarin sodium oral tablets. Teva Pharmaceuticals (per Dailymed), Parsippany, NJ, 2023. DailyMed
- Mar PL, Gopinathannair R, Gengler BE, et al: Drug interactions affecting oral anticoagulant use. Circ Arrhythm Electrophysiol 2022; 15(6):e007956. PubMed
- Schaefer JK, Li Y, Gu X, et al: Association of adding aspirin to warfarin therapy without an apparent indication with bleeding and other adverse events. JAMA Intern Med 2019; 179(4):533-541. PubMed
Keep reading about Warfarin
Keep reading about Aspirin Rectal
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