Amitriptyline and Lacosamide: 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
Lacosamide
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 electrical timing. Lacosamide (Vimpat) can slow the signal that tells your heart to beat, and amitriptyline (Elavil) can affect heart rhythm too. When you take them together, those effects can add up. In some people this could lead to a slower heartbeat or an uneven rhythm.
The good news is this is mostly a theoretical concern, not something that happens to everyone. Your care team can manage it easily, often by checking an ECG (a quick heart tracing) and keeping an eye on how you feel. Please don't stop either medicine on your own. Just talk with your pharmacist or doctor about the best plan.
Mechanism: additive PR-interval prolongation. Lacosamide dose-dependently prolongs the PR interval; amitriptyline (a TCA) also affects cardiac conduction. Neither is a prodrug relevant here; this is a pharmacodynamic, not metabolic, interaction.
Direction/risk: increased risk of PR prolongation, AV block, bradycardia, and ventricular tachyarrhythmia.
- Evidence: theoretical; severity: major; onset: unspecified.
- Management: use concomitantly with caution. Obtain a baseline ECG before starting lacosamide and again at steady-state maintenance dose. Monitor especially closely with IV lacosamide.
- Assess for other conduction-affecting agents and cardiac risk factors.
What happens
An increased risk of PR interval prolongation, AV block, bradycardia, and ventricular tachyarrhythmia
Interaction Deep Dive
Prolongation of the PR interval has been reported with lacosamide. For this reason, using lacosamide together with drugs that influence cardiac conduction, including those that prolong the PR interval, requires caution because of the potential for AV block, bradycardia, and ventricular tachyarrhythmia. An ECG should be recorded prior to starting lacosamide and again once the drug has been titrated to its steady-state maintenance dose12. Furthermore, careful monitoring is warranted when lacosamide is given intravenously2.
Why it happens (mechanism)
Additive PR interval prolongation
How to manage this interaction
The main goal is keeping an eye on your heart's rhythm. This concern is theoretical, but because both drugs can affect cardiac conduction, your care team takes sensible steps:
- They may order an ECG before starting lacosamide and again once you reach your steady maintenance dose.
- They may watch you more closely if lacosamide is given through an IV.
- Your doses may be adjusted and individualized by your care team based on how you respond.
What you should do: keep taking both medicines exactly as prescribed. Tell your pharmacist or doctor if you feel dizzy, faint, unusually slow-heartbeat, or notice palpitations, and mention any other heart medicines you take.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Amitriptyline and Lacosamide together?
Taking amitriptyline with lacosamide can add up to slow or disturb your heart rhythm, so your care team may check an ECG and monitor you; keep taking both as prescribed and report any dizziness, fainting, or palpitations. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Amitriptyline and Lacosamide 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 Lacosamide interaction managed?
The main goal is keeping an eye on your heart's rhythm. This concern is theoretical, but because both drugs can affect cardiac conduction, your care team takes sensible steps: They may order an ECG before starting lacosamide and again once you reach your steady maintenance dose. They may watch you more closely if lacosamide is given through an IV. Your doses may be adjusted and individualized by y… 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 Lacosamide 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 (2)
- Product Information: Motpoly XR oral extended-release capsules, lacosamide oral extended-release capsules. Aucta Pharmaceuticals, Inc, Piscataway, NJ, 2023. DailyMed
- Product Information: VIMPAT(R) oral tablets, intravenous injection, oral solution, lacosamide oral tablets, intravenous injection, oral solution. UCB Inc (per FDA), Smyrna, GA, 2018. DailyMed
Keep reading about Amitriptyline
Keep reading about Lacosamide
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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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