Drug Interaction Report

Ifosfamide and Ketoconazole Topical: Interaction Details

A pharmacist-reviewed analysis of the Ifosfamide 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

Ketoconazole Topical

Extina® Foam Ketozole® Cream Kuric Nizoral AD® Shampoo Nizoral® Cream Nizoral® Shampoo Xolegel®
+

Ifosfamide

Ifex
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 10 documented Ifosfamide interactions, 10 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

Reduced efficacy of ifosfamide, increased ifosfamide exposure and an increased ifosfamide-related adverse reactions

Interaction Deep Dive

Ifosfamide is a substrate for CYP3A42 and ketoconazole is a potent inhibitor of CYP3A4 1. Concomitant use of ketoconazole and ifosfamide may reduce the metabolism of ifosfamide to its active alkylating metabolites, possibly reducing the effectiveness of ifosfamide 2.

Why it happens (mechanism)

Inhibition of CYP3A4-mediated metabolism of ifosfamide to active metabolites

Common questions

Can I take Ifosfamide and Ketoconazole Topical together?

Reduced efficacy of ifosfamide, increased ifosfamide exposure and an increased ifosfamide-related adverse reactions Always confirm with your pharmacist or prescriber before making any change.

How serious is the Ifosfamide and Ketoconazole Topical 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 Ifosfamide 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: IFEX intravenous injection, ifosfamide intravenous injection. Baxter Healthcare Corporation (per FDA), Deerfield, IL, 2024. DailyMed
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Ketoconazole Topical

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All Ketoconazole Topical interactions (546) Ketoconazole Topical drug information
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Ifosfamide

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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:

Ifosfamide + Activated Charcoal Asarabacca Grapefruit Siberian Cocklebur St. John's Wort Acacia Rigidula Acerola Adrafinil + 141 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.