Selpercatinib and Amitriptyline: 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
Selpercatinib
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.
You've been prescribed amitriptyline (for mood, sleep, or nerve pain) along with selpercatinib (Retevmo), a cancer medicine. Both of these can affect your heart's electrical timing, something called the QT interval. When two medicines that do this are taken together, the effect can add up and, in rare cases, lead to an abnormal heartbeat.
This concern is based on how the drugs work rather than a lot of real-world reports, so please don't be alarmed. Your care team can manage this well by checking your heart rhythm with an EKG, keeping your minerals (like potassium and magnesium) in a healthy range, and adjusting doses if needed. Keep taking both as prescribed and talk with your doctor or pharmacist.
Effect: Additive QTc prolongation from concomitant amitriptyline (a TCA with known QT-prolonging effects) and selpercatinib.
- Mechanism: Pharmacodynamic (additive), not a metabolic/prodrug interaction. Neither direction reversal applies.
- Direction: Increased combined QTc effect; increased torsades risk.
- Evidence: Theoretical; severity rated major.
- Onset: Unspecified.
- Management: Assess QTc, electrolytes, and TSH at baseline and periodically (increase frequency with risk factors such as diarrhea). Correct hypokalemia, hypomagnesemia, and hypocalcemia before and during therapy. Withhold, dose-reduce, or discontinue selpercatinib per severity of QTc changes.
What happens
Increased risk of QT interval prolongation
Interaction Deep Dive
When selpercatinib is given together with agents that lengthen the QT interval, the QTc-prolonging action of selpercatinib may be additive. Measure the QT interval, electrolytes, and TSH before starting therapy and at intervals throughout treatment, with the timing of these checks tailored to risk factors such as diarrhea. Any hypokalemia, hypomagnesemia, and hypocalcemia should be corrected both before selpercatinib is begun and while it is being taken. Depending on the severity, selpercatinib should be withheld and the dose reduced, or the drug stopped permanently1.
Why it happens (mechanism)
Additive QT interval prolongation
How to manage this interaction
The good news is this is a manageable situation. Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. Here is what your team typically does:
- Checks an EKG (QT interval) and blood levels of potassium, magnesium, and calcium, plus thyroid (TSH), before starting and periodically during treatment.
- Corrects any low mineral levels and monitors more closely if you have risk factors like diarrhea.
- May adjust or pause the selpercatinib dose depending on your results.
Tell your doctor or pharmacist right away if you feel fainting, dizziness, or a fluttering or pounding heartbeat. Your dose can be individualized by your care team.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Selpercatinib and Amitriptyline together?
Taking amitriptyline with selpercatinib can add to the risk of QT prolongation (a heart rhythm effect), so your team will monitor your EKG and electrolytes and adjust as needed. Keep taking both as prescribed and report any fainting, dizziness, or palpitations. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Selpercatinib and Amitriptyline 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 Selpercatinib and Amitriptyline interaction managed?
The good news is this is a manageable situation. Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. Here is what your team typically does: Checks an EKG (QT interval) and blood levels of potassium, magnesium, and calcium, plus thyroid (TSH), before starting and periodically during treatment. Corrects any low mineral levels and monitors more closely if you h… 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 Selpercatinib or Amitriptyline 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: RETEVMO(R) oral capsules, tablets, selpercatinib oral capsules, tablets. Lilly USA LLC (per FDA), Indianapolis, IN, 2024. DailyMed
Keep reading about Amitriptyline
Keep reading about Selpercatinib
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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