Amitriptyline and Lofexidine: 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
Lofexidine
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.
You've been prescribed amitriptyline (Elavil) and lofexidine. Both of these medicines can affect your heart's rhythm in a similar way. They can each stretch out a part of your heartbeat called the QT interval. When you take them together, that effect can add up, which in rare cases could lead to an irregular heartbeat.
The good news is that this is very manageable. Your care team can keep an eye on your heart with a simple test called an ECG and adjust things if needed. Please keep taking both as prescribed, and let your doctor or pharmacist know if you feel dizzy, faint, or notice a fluttering heartbeat.
Effect: Additive QT interval prolongation with concurrent amitriptyline and lofexidine.
- Mechanism: Both agents independently prolong cardiac repolarization; effects are additive (PD interaction). Neither is a prodrug relevant here.
- Magnitude: Lofexidine added to other QT-prolonging agents increased QTcF by ~9 to 15 msec in trials (buprenorphine/methadone); expect comparable additive risk with a TCA.
- Evidence: Probable. Severity: Major. Onset: Unspecified.
- Management: Baseline and follow-up ECG; monitor QTc, electrolytes (K+, Mg2+), and cardiac symptoms. Individualize dosing and consider alternatives if QTc rises significantly.
What happens
Increased risk of QT interval prolongation
Interaction Deep Dive
Lofexidine therapy has the potential to lengthen the QT interval. When lofexidine was introduced in patients already receiving buprenorphine or methadone (both of which can prolong the QT interval), QTcF rose by 15 and 9.1 milliseconds, respectively. ECG monitoring is advised for patients using concurrent QT prolonging agents1.
Why it happens (mechanism)
Additive QT interval prolongation
How to manage this interaction
This combination can add to each drug's effect on your heart rhythm, so your care team will typically manage it proactively.
- Keep taking both exactly as prescribed unless your doctor tells you otherwise.
- Your team may order an ECG (heart tracing) before starting and periodically afterward.
- They may check your potassium and magnesium levels, since low levels raise the risk.
- Your doses may be adjusted and individualized, or an alternative considered, based on your results.
Call your pharmacist or prescriber if you notice dizziness, fainting, palpitations, or a racing/irregular heartbeat.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) In an investigation involving 18 patients kept on methadone (80 to 120 mg/day), concurrent use of lofexidine (2.88 mg/day) produced a maximum mean rise in QTcF of 9.1 milliseconds compared with the methadone-alone baseline 1.
b) In an investigation involving 21 patients kept on buprenorphine (16 to 24 mg/day), concurrent use of lofexidine (2.88 mg/day) produced a maximum mean rise in QTcF of 15 milliseconds compared with the buprenorphine-alone baseline 1.
Common questions
Can I take Amitriptyline and Lofexidine together?
Amitriptyline and lofexidine can both prolong the QT interval, and together the effect adds up, so your care team will likely monitor your heart with an ECG. Keep taking both as prescribed and report any fainting or irregular heartbeat. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Amitriptyline and Lofexidine 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 Lofexidine interaction managed?
This combination can add to each drug's effect on your heart rhythm, so your care team will typically manage it proactively. Keep taking both exactly as prescribed unless your doctor tells you otherwise. Your team may order an ECG (heart tracing) before starting and periodically afterward. They may check your potassium and magnesium levels, since low levels raise the risk. Your doses may be adjust… 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 Lofexidine 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: LUCEMYRA(TM) oral tablets, lofexidine oral tablets. US WorldMeds LLC (per FDA), Louisville, KY, 2018. DailyMed
Keep reading about Amitriptyline
Keep reading about Lofexidine
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