Drug Interaction Report

Aspirin and Anisindione: Interaction Details

A pharmacist-reviewed analysis of the Aspirin and Anisindione interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Aspirin

Acuprin® Anacin Aspirin Regimen Anacin® Aspirin Regimen Ascriptin® Aspergum Aspergum® Aspi-Cor Aspidrox®
+

Anisindione

No brand names on record
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Jul 11, 2026
Editorial policy · Data sources
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Interaction severity
Major
Potentially serious — often needs a change or close monitoring.
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.

Of 465 documented Aspirin interactions, 327 are rated major — including this one.
Worried about symptoms right now? Contact your pharmacist or prescriber, or call Poison Control at 1-800-222-1222 (US). Call 911 for an emergency.
Onset
delayed
Evidence
established
Severity
Major

What happens

An increased risk of bleeding

Interaction Deep Dive

At high doses (more than 6 grams per day for a 70 kg man), aspirin has a direct hypoprothrombinemic effect2. At lower doses, impairment of platelet function occurs and is of primary concern 34.

Why it happens (mechanism)

Hypoprothrombinemia, inhibition of platelet aggregation, displacement of anisindione from protein binding sites

Literature reports

1 report — tap to read

a) Salicylates may displace coumarins from plasma protein binding sites and enhance the effects of the anticoagulants. More importantly, salicylates exert antiplatelet activity and greatly increase the risk of bleeding when used in conjunction with oral anticoagulants 1.

Common questions

Can I take Aspirin and Anisindione together?

An increased risk of bleeding Always confirm with your pharmacist or prescriber before making any change.

How serious is the Aspirin and Anisindione interaction?

It is rated major. Potentially serious — often needs a change or close monitoring.

How quickly could this interaction happen?

The documented onset is "delayed". Effects tend to build up gradually over days to weeks.

How strong is the evidence for this interaction?

The evidence is graded "established". Well documented — supported by controlled studies or strong clinical data.

Questions for your pharmacist

  • Does my dose of Aspirin or Anisindione 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 (4)

  1. Serlin MJ, Mossman S, Sibeon RG, et al: Interaction between diflunisal and warfarin. Clin Pharmacol Ther 1980; 28:493-498. PubMed
  2. Chan TYK: Adverse interactions between warfarin and nonsteroidal antiinflammatory drugs: mechanisms, clinical significance, and avoidance. Ann Pharmacother 1995; 29:1274-1283. DOI
  3. Chesebro JH, Fuster V, Elveback LR, et al: Trial of combined warfarin plus dipyridamole or aspirin therapy in prosthetic heart valve replacement: danger of aspirin compared with dipyridamole. Am J Cardiol 1983; 51:1537-1541. PubMed
  4. Barrow MV, Quick DT, & Cunningham RW: Salicylate hypoprothrombinemia in rheumatoid arthritis with liver disease. Report of two cases. Arch Intern Med 1967; 120:620-624. DOI
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Aspirin

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All Aspirin interactions (465) Aspirin drug information
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Anisindione

Keep reading about Anisindione

All Anisindione interactions (43)
Also serious with: Aspirin Rectal Danazol Fluoxymesterone Oxandrolone
Beyond drug–drug

These medications also interact with supplements

Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:

Aspirin + Activated Charcoal Asarabacca Beer Danshen Piracetam Siberian Cocklebur Wine Aconite + 234 more
Anisindione + Activated Charcoal Danshen Piracetam Aconite Allspice Aloe Alpha-lipoic Acid Andrographis + 210 more

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This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.