Amitriptyline and Lapatinib: 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
Lapatinib
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 (a medication often used for depression, nerve pain, or sleep) along with lapatinib (a cancer treatment). Both of these medicines can affect the timing of your heartbeat, causing a change called QT prolongation. When taken together, that effect can add up and, in rare cases, lead to an irregular heartbeat.
The good news is that this concern is based mostly on how these drugs work in theory, not on frequent real-world problems. Your care team can manage this easily by keeping an eye on your heart, sometimes with an EKG. Please keep taking both as prescribed, and let your pharmacist or doctor know if you feel dizzy, faint, or notice a fluttering heartbeat.
Effect: Additive QT interval prolongation with concurrent amitriptyline and lapatinib, increasing risk of serious ventricular arrhythmias (including torsades de pointes).
Mechanism: Pharmacodynamic (additive), not a PK interaction. Both agents independently prolong cardiac repolarization. Neither is a prodrug relevant here.
- Direction: Additive QT effect (increased combined risk).
- Onset: Unspecified.
- Evidence: Theoretical.
- Severity: Major.
Management: Use caution. Consider baseline and follow-up ECG, correct electrolytes (K+, Mg2+), review other QT-prolonging agents, and monitor for symptoms. Dosing may be individualized by the care team.
What happens
An increased risk of QT interval prolongation
Interaction Deep Dive
Concurrent administration of amitriptyline and lapatinib warrants caution, as these agents may exert additive effects on the QT interval and heighten the likelihood of serious cardiovascular effects1.
Why it happens (mechanism)
Additive effects on the QT interval
How to manage this interaction
Both drugs can lengthen the QT interval, so a care team's main goal is to watch your heart and reduce added risk.
- Keep taking both exactly as prescribed unless your prescriber tells you otherwise.
- Your team may monitor you more closely, sometimes with an EKG, and may check blood levels of potassium and magnesium.
- Doses may be adjusted and individualized by your care team.
- Tell your pharmacist about all other medicines you take, since some others also affect the QT interval.
- Report fainting, dizziness, or a pounding or irregular heartbeat right away.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Amitriptyline and Lapatinib together?
Amitriptyline and lapatinib can both prolong the QT interval, so together they may raise the risk of a dangerous heart rhythm. Keep taking both as prescribed and let your care team monitor your heart and manage the risk. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Amitriptyline and Lapatinib 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 Lapatinib interaction managed?
Both drugs can lengthen the QT interval, so a care team's main goal is to watch your heart and reduce added risk. Keep taking both exactly as prescribed unless your prescriber tells you otherwise. Your team may monitor you more closely, sometimes with an EKG, and may check blood levels of potassium and magnesium. Doses may be adjusted and individualized by your care team. Tell your pharmacist abou… 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 Lapatinib 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: TYKERB(R) oral tablets, lapatinib oral tablets. GlaxoSmithKline (per FDA), Research Triangle Park, NC, 2011. DailyMed
Keep reading about Amitriptyline
Keep reading about Lapatinib
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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