Amitriptyline and Mavorixafor: 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
Mavorixafor
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.
These two medicines are not meant to be taken together. Amitriptyline (Elavil) is broken down in your body by a liver enzyme called CYP2D6. Mavorixafor (Xolremdi) slows that enzyme down, so amitriptyline can build up to much higher levels than intended.
That extra amitriptyline can cause more of its usual side effects, like drowsiness, dry mouth, constipation, and dizziness. More importantly, both drugs can affect your heart's rhythm, and together they raise the risk of a dangerous heartbeat problem. The good news is your care team knows how to handle this. Please don't change anything on your own, just talk with your doctor or pharmacist so they can make a safe plan.
Contraindicated combination. Mavorixafor is a CYP2D6 inhibitor; amitriptyline is a CYP2D6 substrate (active drug, not a prodrug), so inhibition reduces its clearance and raises exposure.
- Direction: increased amitriptyline exposure and CYP2D6-related adverse effects (anticholinergic, sedation, cardiac).
- Magnitude: with the probe substrate dextromethorphan, mavorixafor 400 mg increased Cmax ~6-fold and AUC ~9-fold.
- Additive risk: both prolong QT, raising risk of TdP, serious arrhythmia, sudden death.
- Evidence: probable.
- Management: obtain ECGs, correct modifiable QT risk factors (electrolytes, other QT drugs), monitor closely; mavorixafor dose reduction or discontinuation may be required.
What happens
Increased CYP2D6 substrate exposure, increased risk of CYP2D6-related adverse events and an increased risk of QT interval prolongation and torsade de pointes
Interaction Deep Dive
Because mavorixafor acts as a CYP2D6 inhibitor, it must not be given together with agents whose clearance relies heavily on CYP2D6. When mavorixafor is used alongside CYP2D6 substrates, the exposure to those substrates can rise, thereby heightening the potential for adverse reactions linked to CYP2D6. In cases where the CYP2D6 substrate also prolongs the QT interval, combining it with mavorixafor further elevates the likelihood of QT prolongation, encompassing torsade de pointes, additional serious arrhythmias, and sudden death. Clinicians should think about performing electrocardiograms, addressing any correctable risk factors for QT prolongation, and keeping patients under observation while the drugs are taken together. It may become necessary to lower the mavorixafor dose or stop the drug. A drug interaction study in healthy subjects found that giving mavorixafor 400 mg together with the CYP2D6 substrate dextromethorphan produced a 6-fold rise in Cmax and a 9-fold rise in AUC1.
Why it happens (mechanism)
Inhibition of CYP2D6-mediated metabolism by mavorixafor; additive QT interval prolongation
How to manage this interaction
This pairing is flagged as one to avoid, but your care team can manage the situation safely. Keep taking both exactly as prescribed until you speak with them, and don't stop anything on your own.
- Your care team may check an ECG to watch your heart rhythm.
- They may correct things that add to QT risk, such as low potassium or magnesium, and review other medicines you take.
- They may adjust or individualize your therapy, and a mavorixafor dose reduction or stopping it may be needed.
Tell your pharmacist or prescriber right away if you feel faint, dizzy, have a racing or irregular heartbeat, or unusual drowsiness.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In a study evaluating drug interactions, giving mavorixafor (a CYP2D6 inhibitor) 400 mg together with dextromethorphan (a CYP2D6 substrate) to healthy subjects produced a 6-fold rise in Cmax and a 9-fold rise in AUC, respectively 1.
Common questions
Can I take Amitriptyline and Mavorixafor together?
Combining amitriptyline with mavorixafor is contraindicated because mavorixafor blocks CYP2D6 and lets amitriptyline build up, raising side-effect and dangerous heart-rhythm risk. Do not change either medicine yourself; contact your doctor or pharmacist promptly to arrange a safe plan. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Amitriptyline and Mavorixafor 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 Amitriptyline and Mavorixafor interaction managed?
This pairing is flagged as one to avoid, but your care team can manage the situation safely. Keep taking both exactly as prescribed until you speak with them, and don't stop anything on your own. Your care team may check an ECG to watch your heart rhythm. They may correct things that add to QT risk, such as low potassium or magnesium, and review other medicines you take. They may adjust or individ… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
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 Mavorixafor 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: XOLREMDI(TM) oral capsules, mavorixafor oral capsules. X4 Pharmaceuticals, Inc. (Per FDA), Boston, MA, 2024. DailyMed
Keep reading about Amitriptyline
Keep reading about Mavorixafor
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