Drug Interaction Report

Quinine and Ketoconazole Topical: Interaction Details

A pharmacist-reviewed analysis of the Quinine and Ketoconazole Topical 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

Quinine

No brand names on record
+

Ketoconazole Topical

Extina® Foam Ketozole® Cream Kuric Nizoral AD® Shampoo Nizoral® Cream Nizoral® Shampoo Xolegel®
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
Contraindicated
These should generally not be used together.
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 79 documented Quinine interactions, 3 are rated contraindicated — 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
probable
Severity
Contraindicated

What happens

Increased quiNINE exposure and an increased risk of QT interval prolongation

Interaction Deep Dive

Concomitant use of ketoconazole with a CYP3A4 substrate known to prolong the QT interval, such as quiNINE is contraindicated, as it may increase quiNINE exposure, increasing the risk for QT prolongation and life-threatening ventricular tachyarrhythmias, including torsades de pointes1. Concomitant use of ketoconazole and quiNINE resulted in an increased AUC (mean, 45%) and decreased clearance (mean, 31%) of quiNINE in a study of 9 healthy subjects. If concomitant use of ketoconazole and quiNINE is clinically warranted, monitor the patient closely for adverse reactions 2.

Why it happens (mechanism)

Inhibition of CYP3A4-mediated metabolism of quiNINE; additive QT interval prolongation

Literature reports

1 report — tap to read

a) Concomitant use of quiNINE hydrochloride (500 mg single dose) and ketoconazole (100 mg twice daily for 3 days) in 9 healthy subjects resulted in a mean 45% increase in quiNINE AUC and a mean 31% reduction in quiNINE clearance compared with quiNINE alone 2.

Common questions

Can I take Quinine and Ketoconazole Topical together?

Increased quiNINE exposure and an increased risk of QT interval prolongation Always confirm with your pharmacist or prescriber before making any change.

How serious is the Quinine and Ketoconazole Topical 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 "probable". Good supporting evidence, though not definitively proven.

Questions for your pharmacist

  • Does my dose of Quinine or Ketoconazole Topical 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)

  1. Product Information: Ketoconazole oral tablet, ketoconazole oral tablet. Taro Pharmaceuticals U.S.A. Inc. (per DailyMed), Hawthorne, NY, 2024. DailyMed
  2. Product Information: QUALAQUIN(R) oral capsules, quinine sulfate oral capsules. AR Scientific, Inc. (per FDA), Philadelphia, PA, 2013. DailyMed
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Quinine

Keep reading about Quinine

All Quinine interactions (79)
Also serious with: Lefamulin Colchicine Goserelin Implant Oxaliplatin Injection
Ketoconazole Topical

Keep reading about Ketoconazole Topical

All Ketoconazole Topical interactions (546) Ketoconazole Topical drug information
Also serious with: Colchicine Conivaptan Crizotinib Dabrafenib
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:

Quinine + Activated Charcoal Cinchona Foxglove Grapefruit Lily-of-the-valley Oleander St. John's Wort Strophanthus + 167 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.