Amitriptyline and Vandetanib: 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
Vandetanib
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 can affect your heart's rhythm. Amitriptyline (Elavil) is an older antidepressant, and vandetanib (Caprelsa) is a cancer medicine. Each one can stretch out a part of your heartbeat called the QT interval. When you take them together, that effect can add up, which can raise the small chance of a dangerous irregular heartbeat.
This concern is based on how the drugs work rather than lots of real-world reports, but it is taken seriously. The good news is your care team can manage this. Please don't stop either medicine on your own. Talk with your doctor or pharmacist, who may check your heart with an ECG and tailor your doses to keep you safe.
Additive QT prolongation risk. Amitriptyline and vandetanib both independently prolong the QTc interval; concurrent use produces additive PD effects and increases the risk of torsades de pointes and serious ventricular arrhythmias.
- Direction: additive PD interaction (not enzyme/prodrug based).
- Evidence: theoretical; mechanism-based.
- Severity: major; combination not recommended.
- Onset: unspecified.
Management: if co-administration is unavoidable, perform more frequent ECG monitoring plus electrolytes (K+, Mg2+). If QTcF exceeds 500 ms, hold therapy until QTcF is below 450 ms, then resume at a reduced dose. Consider a non-QT-prolonging antidepressant alternative where feasible.
What happens
An increased risk of QT interval prolongation
Interaction Deep Dive
Because both amitriptyline and vandetanib lengthen the QT interval, taking them together is discouraged, since their effects on QT prolongation may combine and heighten the likelihood of dangerous ventricular arrhythmias. When concurrent administration cannot be avoided, ECG monitoring should be carried out more often. Should the corrected QT interval (Fridericia; QTcF) exceed 500 milliseconds, treatment should be halted until the QTcF falls below 450 milliseconds, after which it can be restarted at a lower dose1.
Why it happens (mechanism)
Additive effects on QT interval prolongation
How to manage this interaction
Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. Because this combination is generally not recommended, your doctor may look at whether an alternative antidepressant is a better fit.
If both must be used together, your team will typically:
- Check your heart rhythm with more frequent ECGs.
- Watch your QT measurement and pause or lower a dose if it rises too high, then resume carefully.
- May check blood minerals like potassium and magnesium.
Call your doctor right away if you feel fainting, dizziness, palpitations, or an irregular heartbeat. Ask your pharmacist before adding any new medicine.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Amitriptyline and Vandetanib together?
Amitriptyline and vandetanib can both prolong the QT interval, so combining them raises the risk of a dangerous heart rhythm and is generally not recommended. Don't stop either drug on your own; ask your care team, who may use ECG monitoring or an alternative medication. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Amitriptyline and Vandetanib 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 Vandetanib interaction managed?
Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. Because this combination is generally not recommended, your doctor may look at whether an alternative antidepressant is a better fit. If both must be used together, your team will typically: Check your heart rhythm with more frequent ECGs. Watch your QT measurement and pause or lower a dose if it rises too… 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 Vandetanib 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: CAPRELSA(R) oral tablets, vandetanib oral tablets. AstraZeneca Pharmaceuticals LP (Per Manufacturer), Wilmington, DE, 2011. DailyMed
Keep reading about Amitriptyline
Keep reading about Vandetanib
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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