Doxorubicin and Warfarin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Warfarin
Doxorubicin
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 for elevated INR and subsequent bleeding
Interaction Deep Dive
Elevated prothrombin time and subconjunctival hemorrhage were experienced within 1 day in a patient treated with a DOXOrubicin chemotherapy regimen and concomitant warfarin2. The manufacturers do not identify cyclophosphamide, etoposide, methotrexate, DOXOrubicin, mechlorethamine, vincristine, or procarbazine as drugs that interact with warfarin 345678910. Monitor the INR closely and monitor for signs of bleeding when warfarin is used concomitantly with DOXOrubicin chemotherapy regimens. The warfarin dosage may require adjustment to maintain the desired level of anticoagulation. Although no formal drug interaction studies have been done with DOXOrubicin hydrochloride liposome injection, it may interact with drugs known to interact with the conventional formulation of DOXOrubicin 1.
Why it happens (mechanism)
Unknown
Literature reports
1 report — tap to read
a) After starting warfarin, a 62-year-old man treated with cyclophosphamide, DOXOrubicin, etoposide, mechlorethamine, vincristine, procarbazine, methotrexate, and prednisone for lymphoma experienced elevated prothrombin times (PT) on days 1 and 8 and subconjunctival hemorrhage on day 1. His PT ranged from 18 to 20 seconds with a stable warfarin dose. The PT increased to 45, 30, and 36 seconds, respectively, on 3 subsequent cycles after day 1 and 8 of chemotherapy. The PT returned to normal within 1 week of discontinuation of warfarin 2.
Common questions
Can I take Doxorubicin and Warfarin together?
Increased risk for elevated INR and subsequent bleeding Always confirm with your pharmacist or prescriber before making any change.
How serious is the Doxorubicin and Warfarin interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Doxorubicin or Warfarin 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 (10)
- Product Information: DOXIL(R) intravenous injection, doxorubicin HCl liposome intravenous injection. Janssen Products, LP (per FDA), Horsham, PA, 2012. DailyMed
- Seifter EJ, Brooks BJ, & Urba WJ: Possible interactions between warfarin and antineoplastic drugs. Cancer Treat Rep 1985; 69(2):244-245.
- Product Information: COUMADIN(R) oral tablets, IV injection, warfarin sodium oral tablets, IV injection. Bristol-Myers Squibb Company, Princeton, NJ, 2007. DailyMed
- Product Information: CYTOXAN(R) injection, oral tablets, cyclophosphamide injection, oral tablets. Bristol-Myers Squibb Company, Princeton, NJ, 2005.
- Product Information: ETOPOPHOS(R) injection, etoposide phosphate. Bristol-Myers Squibb Company, Princeton, NJ, 2004. DailyMed
- Product Information: methotrexate oral tablets, methotrexate oral tablets. Roxane Laboratories,Inc, Columbus, OH, 2006. DailyMed
- Product Information: MATULANE(R) capsules, procarbazine hydrochloride capsules. Sigma-Tau Pharmaceuticals Inc. Gaithersburg, MD, 2004. DailyMed
- Product Information: vincristine sulfate injection, vincristine sulfate injection. Mayne Pharma (USA) Inc. Paramus, NJ, 2004. DailyMed
- Product Information: MUSTARGEN(R) injection, mechlorethamine hcl injection. Merck & Co. Whitehouse Station, NJ, 2004. DailyMed
- Product Information: RUBEX(R) injection, doxorubicin hydrochloride injection. Mead Johnson, Princeton, NJ, 2001. DailyMed
Keep reading about Warfarin
Keep reading about Doxorubicin
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