Drug Interaction Report

Quinidine and Chloroquine: Interaction Details

A pharmacist-reviewed analysis of the Quinidine and Chloroquine 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

Chloroquine

Aralen®
+

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
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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

An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest)

Interaction Deep Dive

Class Ia antiarrhythmic agents, such as disopyramide, procainamide, and quinidine, may prolong the QT interval and worsen arrhythmias, possibly leading to ventricular tachycardia and ventricular fibrillation234. Rarely, chloroquine may be associated with electrocardiographic changes 1. If concomitant use is required, consider a baseline ECG and on-treatment monitoring when chloroquine is coadministered with class Ia antiarrhythmic drugs.

Why it happens (mechanism)

Additive effects on QT prolongation

Common questions

Can I take Quinidine and Chloroquine 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 Quinidine and Chloroquine 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 Chloroquine 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 (4)

  1. Product Information: ARALEN(R) oral tablets, chloroquine phosphate oral tablets. Sanofi-Aventis U.S. LLC (per FDA), Bridgewater, NJ, 2013. DailyMed
  2. Product Information: disopyramide phosphate oral capsules, disopyramide phosphate oral capsules. Teva Pharmaceuticals USA, Inc. (per DailyMed), North Wales, PA, 2015. DailyMed
  3. Product Information: quinidine gluconate oral extended release tablets, quinidine gluconate oral extended release tablets. Sun Pharmaceutical Industries, Inc. (per DailyMed), Cranbury, NJ, 2014. DailyMed
  4. Product Information: procainamide HCl intravenous injection solution, intramuscular injection solution, procainamide HCl intravenous injection solution, intramuscular injection solution. Hospira, Inc. (per DailyMed), Lake Forest, IL, 2013. DailyMed
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Chloroquine

Keep reading about Chloroquine

All Chloroquine interactions (332) Chloroquine drug information
Also serious with: Levomethadyl Pimozide Mesoridazine 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:

Chloroquine + Activated Charcoal Hibiscus Sabdariffa Biofeedback Coffee Charcoal Dendrobium European Mandrake Fever Bark Ginkgo + 21 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.

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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.