Warfarin and Carboplatin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Warfarin
Carboplatin
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
An elevated INR, trace guaiac-positive black stools, and bruising at the site of blood draws occurred 16 days after a cycle of CARBOplatin and etoposide were reported in a male on warfarin1. Monitor the INR (international normalized ratio) closely and monitor for signs of bleeding when warfarin is used concomitantly with etoposide and CARBOplatin. Warfarin dosage may require adjustment to maintain the desired level of anticoagulation.
Why it happens (mechanism)
Unknown
Literature reports
1 report — tap to read
a) A 74-year-old male stabilized on warfarin for atrial fibrillation had an elevated INR of 12.6, a decreased hemoglobin, and experienced trace guaiac-positive black stools and bruising at the site of blood draws 16 days after a cycle of CARBOplatin and etoposide. His INR (1.15 to 2.11) had been stable for 8 months while on warfarin 5 mg every other day alternating with 7.5 mg every other day. He subsequently required CARBOplatin 180 mg/m(2) IV on day 1 plus etoposide 150 mg/m(2) IV on days 1 to 3 for secondary mediastinal metastases. His baseline INR was 2.11, hemoglobin 12.6 g/dL, and platelets 228 x 10(3)/mm(3). On his follow-up visit, 11 days post-chemotherapy, there was no evidence of bleeding or symptoms of nausea, vomiting, fever, or chills. An INR at the time was not measured but his hemoglobin was 11.1 g/dL. On post-chemotherapy day 16, the patient was admitted to the hospital with fever, diarrhea, nausea, and vomiting. His INR was 12.6, hemoglobin 10.5 g/dL, and platelets 348 x 10(3)/mm(3). He had trace guaiac-positive black watery stools and bruises at the site of blood draws. Warfarin was stopped for 2 days and he was administered phytonadione IV and fresh frozen plasma. Due to suspected gastrointestinal bleeding, decreased hemoglobin, and his history of cardiac and pulmonary disease, packed red blood cells were administered. All subsequent INRs were below 2. The patient refused further chemotherapy 1.
Common questions
Can I take Warfarin and Carboplatin together?
Increased risk for elevated INR and subsequent bleeding Always confirm with your pharmacist or prescriber before making any change.
How serious is the Warfarin and Carboplatin 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 "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 Warfarin or Carboplatin 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 (1)
- Le AT, Hasson NK, & Lum BL: Enhancement of warfarin response in a patient receiving etoposide and carboplatin chemotherapy. Ann Pharmacother 1997; 31(9):1006-1008. PubMed
Keep reading about Warfarin
Keep reading about Carboplatin
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Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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