Phenindione and Apixaban: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Aug 8, 2026 · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Apixaban
Phenindione
No brand names on record
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.
Both of these medicines are blood thinners. Apixaban (Eliquis) blocks a clotting factor called factor Xa, and phenindione is an older anticoagulant that also thins the blood. Taking them together stacks one blood thinner on top of another, which can raise your risk of serious bleeding.
Watch for warning signs like unusual bruising, pink or red urine, black or bloody stools, nosebleeds that won't stop, or coughing or vomiting blood. If any of that happens, get medical help right away or go to the emergency room. The good news is your care team can manage this carefully, and there is even a medicine that can reverse apixaban's effect if needed. Talk with your doctor or pharmacist about why you are on both.
Mechanism: additive anticoagulation. Apixaban is a direct factor Xa inhibitor; phenindione is a vitamin K antagonist. Combined use produces additive antithrombotic effect and increased bleeding risk (neither drug is affected via prodrug activation here).
- Direction: increased anticoagulant effect / bleeding risk.
- Magnitude: PD interaction studies with apixaban plus enoxaparin showed a 50-60% rise in anti-FXa activity; expect additive risk with any anticoagulant.
- Evidence: probable. Severity: major.
- Management: avoid concurrent anticoagulants unless clearly indicated. Discontinue apixaban if active pathological bleeding occurs; PD effect persists at least 24 hours. Reversal agent available; PCC, aPCC, or rFVIIa may be considered. Routine PT/INR/aPTT or anti-FXa monitoring is not useful when PCC is used.
What happens
An increased risk of bleeding and can cause serious, potentially fatal bleeding
Interaction Deep Dive
Giving apixaban, a factor Xa inhibitor, together with another anticoagulant heightens the likelihood of bleeding. Pharmacodynamic drug interaction studies of apixaban showed a 50% to 60% rise in anti-factor Xa activity when apixaban was administered alongside enoxaparin. Should active pathological bleeding develop, apixaban should be stopped. There is an agent available to reverse apixaban's anti-factor Xa activity. Apixaban's pharmacodynamic effect can be anticipated to last for a minimum of 24 hours following the final dose. Patients should be counseled on the signs and symptoms of blood loss and instructed to report these immediately or present to an emergency room. Options that may be considered include prothrombin complex concentrate (PCC), activated prothrombin complex concentrate, or recombinant factor VIIa. If PCCs are administered, it is not helpful, and therefore not recommended, to monitor apixaban's anticoagulant effect via a clotting test (PT, INR, or aPTT) or anti-factor Xa (FXa) activity. The absorption of apixaban is decreased by activated oral charcoal, which consequently reduces apixaban exposure1.
Why it happens (mechanism)
Additive anticoagulation
How to manage this interaction
Keep taking both exactly as prescribed unless your prescriber tells you otherwise. Do not stop or change either medicine on your own.
- Your care team may keep a closer eye on you because using two anticoagulants together raises bleeding risk.
- Learn the signs of bleeding: unusual bruising, blood in urine or stool, black stools, prolonged nosebleeds, coughing or vomiting blood, severe headache, or dizziness.
- Report these immediately or go to an emergency room.
- Reassuringly, a reversal agent for apixaban exists, and its effect fades over about 24 hours after the last dose.
Ask your pharmacist or doctor whether you truly need both agents and how they plan to monitor you.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In investigations of pharmacodynamic drug interactions involving apixaban, an increase of 50% to 60% in anti-factor Xa activity was noted when apixaban and enoxaparin were given together 1.
Common questions
Can I take Phenindione and Apixaban together?
Apixaban and phenindione are both blood thinners, so together they meaningfully raise the risk of serious bleeding. Keep taking both as prescribed, watch closely for any bleeding, and seek help immediately if it occurs. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Phenindione and Apixaban 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 is the Phenindione and Apixaban interaction managed?
Keep taking both exactly as prescribed unless your prescriber tells you otherwise. Do not stop or change either medicine on your own. Your care team may keep a closer eye on you because using two anticoagulants together raises bleeding risk. Learn the signs of bleeding: unusual bruising, blood in urine or stool, black stools, prolonged nosebleeds, coughing or vomiting blood, severe headache, or di… Management is individual — always follow your own care team's guidance.
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 Phenindione or Apixaban 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)
- Product Information: ELIQUIS(R) oral film coated tablets, apixaban oral film coated tablets. Bristol-Myers Squibb Company (per Dailymed), Princeton, NJ, 2024. DailyMed
Keep reading about Apixaban
Keep reading about Phenindione
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:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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