Amitriptyline and Tamoxifen: 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
Tamoxifen
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 amitriptyline (Elavil) and tamoxifen (Nolvadex) can each have a small effect on your heart's electrical rhythm, something called QT prolongation. When two medicines that do this are taken together, that effect can add up, which may slightly raise the chance of an abnormal heartbeat.
I want to be clear that this is a theoretical concern based on how these drugs behave, not something proven to happen often. Please don't stop either medicine on your own. Just let your pharmacist or doctor know you take both so they can keep an eye on things and make sure this is a safe combination for you.
Effect: Additive risk of QT interval prolongation with concurrent amitriptyline and tamoxifen.
Mechanism: Pharmacodynamic (additive), not a metabolic/PK interaction. Both agents are independently associated with QTc prolongation.
Evidence: Theoretical. Severity: Major. Onset: Unspecified.
- Assess baseline and cumulative QT risk factors (electrolytes, bradycardia, other QT-prolonging drugs, hepatic function, family history).
- Consider ECG monitoring and periodic electrolyte checks (K+, Mg2+), particularly at initiation or dose changes.
- Correct hypokalemia/hypomagnesemia; dosing should be individualized by the care team.
What happens
An increased risk of QT interval prolongation
Interaction Deep Dive
Taking tamoxifen alongside medications known to prolong the QT interval may raise the likelihood of QT interval prolongation1.
Why it happens (mechanism)
Additive QT interval prolongation
How to manage this interaction
Good news: this is a manageable combination, and many patients take both safely under supervision.
- Keep taking both exactly as prescribed unless your care team tells you otherwise.
- Your team may monitor you more closely, which can include an ECG (heart tracing) and blood tests to check potassium and magnesium.
- Doses may be adjusted and individualized by your care team based on your overall heart risk.
- Tell your pharmacist about any other medicines you take, since some also affect heart rhythm.
Contact your doctor promptly if you feel fainting, dizziness, or a pounding or irregular heartbeat.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Amitriptyline and Tamoxifen together?
Amitriptyline and tamoxifen can each nudge your heart rhythm (QT interval), and together the effect may add up, so your care team may check an ECG and electrolytes. Keep taking both as prescribed and report any fainting or irregular heartbeat. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Amitriptyline and Tamoxifen 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 Amitriptyline and Tamoxifen interaction managed?
Good news: this is a manageable combination, and many patients take both safely under supervision. Keep taking both exactly as prescribed unless your care team tells you otherwise. Your team may monitor you more closely, which can include an ECG (heart tracing) and blood tests to check potassium and magnesium. Doses may be adjusted and individualized by your care team based on your overall heart r… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
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 Tamoxifen 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: Tamoxifen Citrate oral tablets, tamoxifen citrate oral tablets. Teva Pharmaceuticals (per DailyMed), Parsippany, NJ, 2025. DailyMed
Keep reading about Amitriptyline
Keep reading about Tamoxifen
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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