Mesoridazine 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
Mesoridazine
No brand names on record
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), which is used for mood and sometimes nerve pain, and mesoridazine, an older antipsychotic, can each stretch out a part of your heartbeat called the QT interval. When you take them together, that effect can add up and, in rare cases, lead to a dangerous irregular heartbeat.
Because of this, taking these two together is generally not recommended. Please don't stop either one on your own. Reach out to your doctor or pharmacist, who can review your medicines and choose a safer plan for you.
Effect: Additive QT interval prolongation with increased risk of serious ventricular arrhythmias (including torsades de pointes).
Mechanism: Both agents independently delay cardiac repolarization; combining a TCA (amitriptyline) with mesoridazine (a phenothiazine with pronounced QT effects) produces additive QTc prolongation. This is a pharmacodynamic interaction, not a metabolic one; neither is a relevant prodrug here.
Evidence: Theoretical, but severity on file is contraindicated. Onset unspecified.
- Avoid concomitant use.
- If unavoidable, baseline and follow-up ECG/QTc, electrolytes (K+, Mg2+), and cardiac monitoring are warranted.
- Consider an alternative agent lacking QT liability.
What happens
An increased risk of QT interval prolongation
Interaction Deep Dive
Using mesoridazine together with agents known to prolong the QT interval is contraindicated, because such combined use may heighten the likelihood of QT prolongation and serious ventricular arrhythmias1.
Why it happens (mechanism)
Additive QT interval prolongation
How to manage this interaction
This combination is flagged as one to avoid because both drugs can lengthen the QT interval and, together, raise the risk of a dangerous heart rhythm.
- Keep taking both as prescribed for now, and do not stop either drug on your own.
- Contact your prescriber or pharmacist promptly so they can review this pairing.
- Your care team may switch one drug to a safer alternative, or if both are truly needed, monitor you more closely with ECGs and blood tests (like potassium and magnesium).
- Get urgent help if you feel fainting, a racing or irregular heartbeat, or dizziness.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Mesoridazine and Amitriptyline together?
Amitriptyline and mesoridazine can each prolong the QT interval, and using them together is considered contraindicated because of the risk of serious heart rhythm problems. Contact your doctor or pharmacist so they can adjust your regimen. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Mesoridazine and Amitriptyline interaction?
It is rated contraindicated. These should generally not be used together.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Mesoridazine and Amitriptyline interaction managed?
This combination is flagged as one to avoid because both drugs can lengthen the QT interval and, together, raise the risk of a dangerous heart rhythm. Keep taking both as prescribed for now, and do not stop either drug on your own. Contact your prescriber or pharmacist promptly so they can review this pairing. Your care team may switch one drug to a safer alternative, or if both are truly needed,… 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 Mesoridazine 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: SERENTIL(R) oral tablets, injection, oral solution, mesoridazine besylate oral tablets, injection, oral solution. Boehringer Ingelheim Pharmaceuticals,Inc, Ridgefield, CT, 2001.
Keep reading about Amitriptyline
Keep reading about Mesoridazine
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:
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