Imlunestrant 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
Imlunestrant
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 imlunestrant exposure and an increased risk of imlunestrant-related adverse reactions
Interaction Deep Dive
Avoid concomitant use of imlunestrant (CYP3A substrate) with strong CYP3A inhibitors as it may increase imlunestrant exposure, which may increase imlunestrant-related adverse reactions. If concomitant use cannot be avoided, reduce imlunestrant dosage to 200 mg once daily. In drug interaction study, concomitant use of imlunestrant with itraconazole (strong CYP3A inhibitor) for multiple days increased imlunestrant AUC and Cmax by 2.1-fold and 1.9-fold, respectively1.
Why it happens (mechanism)
Inhibition of CYP3A-mediated metabolism of imlunestrant
Literature reports
1 report — tap to read
a) In drug interaction study, concomitant use of imlunestrant with itraconazole (strong CYP3A inhibitor) for multiple days increased imlunestrant AUC and Cmax by 2.1-fold and 1.9-fold, respectively 1.
Common questions
Can I take Imlunestrant and Ketoconazole Topical together?
Increased imlunestrant exposure and an increased risk of imlunestrant-related adverse reactions Always confirm with your pharmacist or prescriber before making any change.
How serious is the Imlunestrant 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 Imlunestrant 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: INLURIYO oral tablets, imlunestrant oral tablets. Lilly USA, LLC (per FDA), Indianapolis, IN, 2025. DailyMed
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