Abemaciclib and Posaconazole: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 10, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Posaconazole
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.
Here's what's going on. Posaconazole (Noxafil) is a strong antifungal that slows down a liver enzyme called CYP3A4. That enzyme is the same one your body uses to break down abemaciclib (Verzenio), your cancer medicine. So when you take both, the abemaciclib can build up higher than usual in your blood.
Higher levels can mean more side effects, like diarrhea, tiredness, or lower blood counts. The good news is this is very manageable. Your cancer team knows how to handle it, often by adjusting your abemaciclib dose while you're on the antifungal. Please don't change anything on your own. Just make sure both doctors know you take both.
Mechanism: Posaconazole is a strong CYP3A4 inhibitor; abemaciclib is a CYP3A4 substrate (active metabolite included). Inhibition reduces abemaciclib metabolism, increasing plasma exposure of parent drug and active metabolite, raising toxicity risk (diarrhea, neutropenia, hepatotoxicity, VTE).
- Direction: increased abemaciclib effect/exposure
- Evidence: theoretical; onset: unspecified
- Management per labeling: if starting dose was 200 mg or 150 mg BID, reduce to 100 mg BID; if already reduced to 100 mg BID for adverse reactions, further reduce to 50 mg BID.
- On inhibitor discontinuation: after 3-5 half-lives of posaconazole, resume the pre-inhibitor abemaciclib dose.
Monitor for CDK4/6 inhibitor toxicities and adjust individually.
What happens
Increased abemaciclib plasma concentration
Interaction Deep Dive
Taking abemaciclib together with a potent CYP3A4 inhibitor can raise plasma concentrations of both abemaciclib and its active metabolite, potentially heightening toxicity. When these agents are given together and the initial abemaciclib dose was 200 mg or 150 mg twice daily, lower the abemaciclib dose to 100 mg twice daily. For patients whose dose has already been cut to 100 mg twice daily owing to adverse reactions, decrease abemaciclib further to 50 mg twice daily. Upon stopping the strong CYP3A inhibitor, and after 3-5 half-lives of that inhibitor have elapsed, return the abemaciclib dose to the level administered prior to starting the strong inhibitor1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated abemaciclib metabolism
How to manage this interaction
This interaction can be managed. Keep taking both medicines exactly as prescribed unless your oncology team tells you otherwise.
- Your team may lower your abemaciclib dose while you are on posaconazole. Per labeling, a starting dose of 200 mg or 150 mg twice daily is reduced to 100 mg twice daily, and if you were already at 100 mg twice daily, it may go to 50 mg twice daily.
- When posaconazole is stopped, your team will typically raise the dose back to your previous level after the antifungal has cleared.
- Watch for and report diarrhea, unusual tiredness, fever, or signs of infection.
Make sure every prescriber knows you take both drugs.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) Drug interaction studies predict that giving abemaciclib together with itraconazole (a strong CYP3A inhibitor) will raise the AUC of abemaciclib along with its active metabolites (M2, M18 and M20) by 2.2-fold 1.
b) In drug interaction studies conducted in cancer patients, administering a single 50 mg dose of abemaciclib (0.3 times the approved 150 mg dose) alongside clarithromycin 500 mg twice daily (a strong CYP3A inhibitor) raised the AUC(0 to infinity) of abemaciclib together with its active metabolites (M2, M18, and M20) by 1.7-fold relative to abemaciclib given alone 1.
Common questions
Can I take Abemaciclib and Posaconazole together?
Posaconazole can raise abemaciclib levels and side-effect risk, so your oncology team will likely lower the abemaciclib dose while you're on the antifungal and raise it back afterward. Keep taking both as prescribed and report new side effects. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abemaciclib and Posaconazole interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Abemaciclib and Posaconazole interaction managed?
This interaction can be managed. Keep taking both medicines exactly as prescribed unless your oncology team tells you otherwise. Your team may lower your abemaciclib dose while you are on posaconazole. Per labeling, a starting dose of 200 mg or 150 mg twice daily is reduced to 100 mg twice daily, and if you were already at 100 mg twice daily, it may go to 50 mg twice daily. When posaconazole is st… Management is individual — always follow your own care team's guidance.
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 Abemaciclib or Posaconazole 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 anything you'd monitor while I'm on both?
References (1)
- Product Information: VERZENIO(TM) oral tablets, abemaciclib oral tablets. Lilly USA LLC (per FDA), Indianapolis, IN, 2017. DailyMed
Keep reading about Posaconazole
Keep reading about Abemaciclib
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