Isoflurane and Mefloquine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Isoflurane
Mefloquine
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
Isoflurane has been associated with prolongation of the QT interval1. Even though no formal drug interaction studies have been done, the coadministration of mefloquine with other drugs which can prolong the QTc interval, such as isoflurane is not recommended 2, as it may increase risk of QT interval prolongation with rare instances of torsade de pointes. Hence if coadministered, monitor QT interval 3.
Why it happens (mechanism)
Additive QT interval prolongation
Common questions
Can I take Isoflurane 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 Isoflurane and Mefloquine 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 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 Isoflurane 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 (3)
- Owens R: Risk assessment for antimicrobial agent-induced QTc prolongation and torsades de pointes. Pharmacother 2001; 21(3):310-319.
- Product Information: Lariam(R), mefloquine. Roche Laboratories, Nutley, NJ, 1999. DailyMed
- Product Information: FORANE inhalation liquid, isoflurane inhalation liquid. Baxter Healthcare Corporation (per FDA), Deerfield, IL, 2024. DailyMed
Keep reading about Isoflurane
Keep reading about Mefloquine
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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