Levomethadyl and Mefloquine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Mefloquine
Levomethadyl
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.
What happens
An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest)
Interaction Deep Dive
Levomethadyl can prolong the QT interval in some patients, which may result in ventricular tachycardia, ventricular fibrillation, and torsades de pointes. The concomitant treatment of levomethadyl with other drugs known to prolong the QT interval, such as mefloquine, is contraindicated12.
Why it happens (mechanism)
Additive cardiac effects
Common questions
Can I take Levomethadyl and Mefloquine together?
An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest) Always confirm with your pharmacist or prescriber before making any change.
How serious is the Levomethadyl and Mefloquine 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 strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Levomethadyl or Mefloquine 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: Orlaam(R), levomethadyl acetate. Roxane Laboratories, Columbus, OH, 2001.
- Davis TME, Dembo LG, & Kaye-Eddie SA: Neurological, cardiovascular and metabolic effects of mefloquine in healthy volunteers: a double-blind, placebo-controlled trial. Br J Clin Pharmacol 1996; 42:415-421. PubMed
Keep reading about Mefloquine
Keep reading about Levomethadyl
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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