Drug Interaction Report

Quinidine and Mefloquine: Interaction Details

A pharmacist-reviewed analysis of the Quinidine and Mefloquine interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Mefloquine

Lariam®
+

Quinidine

Cardioquin® Cin-Quin® Duraquin® Quinact® Quinaglute® Quinalan® Quinatime® Quinidex®
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
LinkedIn
Interaction severity
Major
Potentially serious — often needs a change or close monitoring.
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.

Of 91 documented Quinidine interactions, 80 are rated major — including this one.
Worried about symptoms right now? Contact your pharmacist or prescriber, or call Poison Control at 1-800-222-1222 (US). Call 911 for an emergency.
Onset
unspecified
Evidence
theoretical
Severity
Major

What happens

Increased risk of QT prolongation

Interaction Deep Dive

Mefloquine and quinidine should not be administered concurrently1. Mefloquine was associated with significant QT prolongation in a study of 46 healthy subjects 2, and quinidine has also been associated with QT prolongation 3. If quinidine and mefloquine are both used during the initial treatment of severe malaria, mefloquine should be administered at least 12 hours after the last dose of quinidine 1.

Why it happens (mechanism)

Additive effect on QT interval

Common questions

Can I take Quinidine and Mefloquine together?

Increased risk of QT prolongation Always confirm with your pharmacist or prescriber before making any change.

How serious is the Quinidine 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 Quinidine 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)

  1. Product Information: LARIAM(R) oral tablets, mefloquine hcl oral tablets. Roche Laboratories, Inc, Nutley, NJ, 2009.
  2. 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
  3. Benton RE, Sale M, Flockhart DA, et al: Greater quinidine-induced QTc interval prolongation in women. Clin Pharmacol Ther 2000; 67:413-418. PubMed
Was this write-up helpful?
Mefloquine

Keep reading about Mefloquine

All Mefloquine interactions (256) Mefloquine drug information
Also serious with: Mesoridazine Levomethadyl Pimozide Levoketoconazole
Quinidine

Keep reading about Quinidine

All Quinidine interactions (91) Quinidine drug information
Also serious with: Colchicine Ketoconazole Topical Lefamulin Dofetilide
Beyond drug–drug

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:

Mefloquine + Activated Charcoal Biofeedback Coffee Charcoal Dendrobium European Mandrake Ginkgo Glucomannan Guar Gum + 15 more
Quinidine + Activated Charcoal American Hellebore Arsenic Beer Cesium Cinchona Ephedra Grapefruit + 199 more

major · moderate · minor — check everything you take with our drug–supplement interaction checker.

Check another combination

Our instant two-drug interaction checker is almost here.

Coming soon

The instant two-drug checker is on its way.

In the meantime, browse the directory below to look up any drug and see its documented interactions.

Still have questions about this combination?

Every question gets a real answer from a licensed pharmacist — free, and usually within a day.

Ask the pharmacist
This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.