Amitriptyline and Dicumarol: 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
Amitriptyline
Dicumarol
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.
Here's what's going on. Dicumarol is a blood thinner, and amitriptyline (Elavil) is an antidepressant that can also help with things like nerve pain and sleep. When you take them together, amitriptyline can cause your body to hold onto more dicumarol and absorb more of it. That means the blood thinner can build up and work more strongly than expected, which raises your risk of bleeding.
The good news is this is very manageable. Blood thinners are watched closely anyway with a simple blood test (the INR). Keep taking both exactly as prescribed, and let your pharmacist or doctor know you're on both so they can check your levels and adjust if needed.
Effect: TCAs may increase the half-life and bioavailability of oral anticoagulants, raising bleeding risk. Neither drug is a prodrug; amitriptyline increases dicumarol exposure directly.
Mechanism: decreased dicumarol metabolism plus increased dicumarol absorption.
- Direction: increased dicumarol effect (enhanced anticoagulation).
- Onset: delayed. Evidence: probable. Severity: moderate.
- Note: considerable interindividual variability. Dicumarol is a narrow-therapeutic-index agent, so small shifts matter.
Management: Monitor PT ratio/INR closely when starting or stopping amitriptyline, and reassess periodically during concurrent use. Individualize dicumarol dose to maintain target anticoagulation.
What happens
An increased risk of bleeding
Interaction Deep Dive
Oral anticoagulants may exhibit 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 dicumarol metabolism; increased dicumarol absorption
How to manage this interaction
This is manageable with monitoring. Your care team already tracks anticoagulation with the INR blood test, and that test is the key tool here.
- Keep taking both medications exactly as prescribed unless your doctor tells you otherwise.
- Expect closer INR checks when amitriptyline is started or stopped, and periodic checks while you take both.
- Your dicumarol dose may need to be adjusted and individualized by your care team to keep your anticoagulation in the right range.
- Watch for signs of bleeding (unusual bruising, nosebleeds, blood in urine or stool, gums bleeding) and report them promptly.
Tell your pharmacist and prescriber that you take both so they can plan the monitoring.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
3 reports — tap to read
a) In a trial involving healthy volunteers, taking nortriptyline or amitriptyline at the same time led to higher dicumarol concentrations and a longer plasma half-life of dicumarol, though this effect was not seen consistently across all participants 1. No such effect occurred with warfarin.
b) A single oral dose of bishydroxycoumarin given after eight days of nortriptyline produced a significantly extended half-life and a reduced volume of distribution of the coumarin anticoagulant in six healthy volunteers 2. The proposed mechanism was decreased bishydroxycoumarin metabolism and/or changed coumarin absorption.
c) Dosing of drugs was examined in 16 patients receiving long-term anticoagulant therapy who were also taking TCAs concurrently 3. TCAs disrupted the stability of anticoagulant control, resulting in frequent adjustments to anticoagulant doses. Suppression of coumarin metabolism was the suggested mechanism.
Common questions
Can I take Amitriptyline and Dicumarol together?
Amitriptyline can boost the blood-thinning effect of dicumarol and raise bleeding risk, so your team will monitor your INR closely and adjust the dicumarol dose as needed. Keep taking both as prescribed and report any unusual bleeding. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Amitriptyline and Dicumarol 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 Dicumarol interaction managed?
This is manageable with monitoring. Your care team already tracks anticoagulation with the INR blood test, and that test is the key tool here. Keep taking both medications exactly as prescribed unless your doctor tells you otherwise. Expect closer INR checks when amitriptyline is started or stopped, and periodic checks while you take both. Your dicumarol dose may need to be adjusted and individual… 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 Dicumarol 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 Amitriptyline
Keep reading about Dicumarol
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