Isavuconazonium and Ketoconazole Topical: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Ketoconazole Topical
Isavuconazonium
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
Increased isavuconazole (active form of isavuconazonium sulfate) exposure
Interaction Deep Dive
Isavuconazole (active form of isavuconazonium sulfate) Cmax and AUC increased significantly following coadministration with multiple doses of ketoconazole (a strong CYP3A4 inhibitor) during drug interaction studies. Therefore, concomitant use of isavuconazonium sulfate (a prodrug of isavuconazole, a sensitive CYP3A4 substrate) and a strong CYP3A4 inhibitor is contraindicated due to the potential for significantly increased exposure of isavuconazole1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated isavuconazole (active form of isavuconazonium sulfate) metabolism
Literature reports
1 report — tap to read
a) Isavuconazole Cmax and AUC were increased by 9% and 422%, respectively, following coadministration of a single dose of isavuconazonium sulfate 200 mg (prodrug of isavuconazole) with multiple doses of ketoconazole 200 mg twice daily for 24 days 1.
Common questions
Can I take Isavuconazonium and Ketoconazole Topical together?
Increased isavuconazole (active form of isavuconazonium sulfate) exposure Always confirm with your pharmacist or prescriber before making any change.
How serious is the Isavuconazonium 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 Isavuconazonium 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 (1)
- Product Information: CRESEMBA(R) oral capsules, intravenous injection, isavuconazonium sulfate oral capsules, intravenous injection. Astellas Pharma US Inc (per FDA), Northbrook, IL, 2023. DailyMed
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