Amitriptyline and Acenocoumarol: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 2, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Acenocoumarol
No brand names on recordAmitriptyline
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.
Here's what's going on. Acenocoumarol is a blood thinner, and amitriptyline (Elavil) is an antidepressant. When you take them together, the amitriptyline can slow down how your body clears the blood thinner and let more of it get absorbed. That means the blood thinner can build up and work a little too strongly, which raises your chance of bleeding or bruising.
The good news is your care team can manage this easily. They may check your INR (a simple blood test that measures how thin your blood is) more often and fine-tune your blood thinner dose. Watch for unusual bruising, nosebleeds, or bleeding that won't stop, and let your pharmacist or doctor know if you notice anything.
Effect: TCAs (amitriptyline) may increase the half-life and bioavailability of acenocoumarol, enhancing its anticoagulant effect and raising bleeding risk. Neither agent is activated to its effect by the other, so inhibition here means more active anticoagulant.
- Mechanism: decreased acenocoumarol metabolism plus increased GI absorption.
- Direction: increased acenocoumarol exposure and effect.
- Onset: delayed; Evidence: probable; Severity: moderate.
- NTI drug (acenocoumarol): even small shifts matter; wide interindividual variability.
Management: Monitor INR closely when starting or stopping amitriptyline and periodically during co-therapy. Anticipate anticoagulant dose adjustments to maintain target INR.
What happens
An increased risk of bleeding
Interaction Deep Dive
Oral anticoagulants may experience a prolonged half-life and enhanced bioavailability when combined with tricyclic antidepressants (TCAs)23. The extent of this effect can vary substantially from one individual to another1.
Why it happens (mechanism)
Decreased acenocoumarol metabolism; increased acenocoumarol absorption
How to manage this interaction
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. This combination is manageable with monitoring.
- Expect more frequent INR checks, especially when amitriptyline is started, stopped, or its dose changes.
- Your acenocoumarol dose may need to be adjusted and individualized by your care team to keep your INR in the target range.
- Watch for and report any unusual bleeding, bruising, blood in urine or stool, or nosebleeds that won't stop.
- Ask your pharmacist before adding any new medicines, including over-the-counter pain relievers.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
3 reports — tap to read
a) In an investigation involving healthy volunteers, the simultaneous administration of nortriptyline or amitriptyline produced a rise in dicumarol concentrations along with a longer plasma half-life of dicumarol, though this response was not uniform across all participants 1. No such effect was seen with warfarin.
b) Administration of a single oral dose of bishydroxycoumarin following 8 days of nortriptyline led to a markedly extended half-life and a reduced volume of distribution of the coumarin anticoagulant in 6 healthy volunteers 2. The proposed mechanism was decreased metabolism of bishydroxycoumarin and/or a change in coumarin absorption.
c) Drug dosing was examined in 16 patients receiving long-term anticoagulant therapy who concurrently took TCAs 3. The TCAs disturbed the consistency of anticoagulant control, resulting in repeated adjustments to anticoagulant doses. The suggested mechanism was inhibition of coumarin metabolism.
Common questions
Can I take Amitriptyline and Acenocoumarol together?
Amitriptyline can strengthen acenocoumarol and raise bleeding risk, so your team will monitor your INR closely and adjust your blood thinner dose as needed. Keep taking both as prescribed and report any unusual bleeding or bruising. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Amitriptyline and Acenocoumarol interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How is the Amitriptyline and Acenocoumarol interaction managed?
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. This combination is manageable with monitoring. Expect more frequent INR checks, especially when amitriptyline is started, stopped, or its dose changes. Your acenocoumarol dose may need to be adjusted and individualized by your care team to keep your INR in the target range. Watch for and report any unusual bleedi… 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 Amitriptyline or Acenocoumarol 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 anything you'd monitor while I'm on both?
References (3)
- Pond SM, Graham GG, Birkett DJ, et al: Effects of tricyclic antidepressants on drug metabolism. Clin Pharmacol Ther 1975; 18:191-199. PubMed
- Vesell ES, Passananti GT, & Greene FE: Impairment of drug metabolism in man by allopurinol and nortriptyline. N Engl J Med 1970; 283:1484-1488. PubMed
- Williams JR, Griffin JP, & Parkins A: Effect of concomitantly administered drugs on the control of long term anticoagulant therapy. Q J Med 1976; 45:63-73. DOI
Keep reading about Acenocoumarol
Keep reading about Amitriptyline
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