Ketoconazole Topical and Abemaciclib: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Ketoconazole Topical
Abemaciclib
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 abemaciclib exposure
Interaction Deep Dive
Coadministration of ketoconazole (a strong CYP3A4 inhibitor) with CYP3A4 substrates, such as abemaciclib may result in significantly increased abemaciclib and its active metabolite exposure, and may lead to increased toxicity. There is a predicted increase in the AUC of abemaciclib by up to 16-fold with concomitant use1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of abemaciclib
Literature reports
1 report — tap to read
a) In drug interaction studies, there is a predicted increase in the AUC of abemaciclib by up to 16-fold with concomitant use of ketoconazole 1.
Common questions
Can I take Ketoconazole Topical and Abemaciclib together?
Increased abemaciclib exposure Always confirm with your pharmacist or prescriber before making any change.
How serious is the Ketoconazole Topical and Abemaciclib 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 Ketoconazole Topical or Abemaciclib 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: VERZENIO(R) oral tablets, abemaciclib oral tablets. Lilly USA LLC (per FDA), Indianapolis, IN, 2024. DailyMed
Keep reading about Ketoconazole Topical
Keep reading about Abemaciclib
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