Abemaciclib and Itraconazole: 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
Itraconazole
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. Itraconazole (Sporanox) is a strong antifungal that slows down a liver enzyme called CYP3A4. Your body uses that same enzyme to break down abemaciclib (Verzenio), your cancer medicine. When itraconazole slows the enzyme, abemaciclib can build up to higher levels than intended.
Higher levels can mean more side effects, like diarrhea, low blood counts, tiredness, or nausea. The good news is this is very manageable. If your doctor ever needs to use both together, they can simply lower your abemaciclib dose and keep a closer eye on you. Please don't change anything on your own. Just let your pharmacist or doctor know you take both.
Mechanism: Itraconazole is a strong CYP3A4 inhibitor; abemaciclib is a CYP3A4 substrate (active parent plus active metabolite). Inhibition reduces metabolic clearance, raising abemaciclib exposure (AUC/Cmax) and potentially increasing toxicity.
- Direction: increased abemaciclib effect and toxicity risk
- Evidence: theoretical/label-based
- Onset: unspecified
Management: 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, reduce further to 50 mg BID. On discontinuing itraconazole, resume the pre-inhibitor dose after 3 to 5 inhibitor half-lives. Monitor for diarrhea, cytopenias, hepatotoxicity, and fatigue.
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 abemaciclib was started at either 200 mg or 150 mg twice daily, lower the abemaciclib dose to 100 mg twice daily. For patients whose dose was already reduced to 100 mg twice daily because of adverse reactions, cut the abemaciclib dose further to 50 mg twice daily. Once the strong CYP3A inhibitor is stopped, wait for 3-5 half-lives of the inhibitor to elapse, then raise the abemaciclib dose back to the level used prior to starting the strong inhibitor1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated abemaciclib metabolism
How to manage this interaction
What your care team may do:
- Lower your abemaciclib dose while you are on itraconazole (for example, from 200 or 150 mg twice daily down to 100 mg twice daily, and if you were already at 100 mg twice daily for side effects, down to 50 mg twice daily).
- Watch you more closely for side effects like diarrhea, low blood counts, or fatigue.
- Raise your dose back to your usual amount a few days after the itraconazole is stopped.
What you should do: Keep taking both exactly as prescribed, and tell your pharmacist or oncologist that you are on both so they can tailor your dose. Report new or worsening side effects promptly.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) In drug interaction studies, giving abemaciclib together with itraconazole (a strong CYP3A inhibitor) is projected to 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 dosage) alongside clarithromycin 500 mg twice daily (a strong CYP3A inhibitor) raised the AUC(0 to infinity) of abemaciclib plus its active metabolites (M2, M18, and M20) by 1.7-fold relative to abemaciclib given alone 1.
Common questions
Can I take Abemaciclib and Itraconazole together?
Itraconazole can raise abemaciclib levels and side effects, but your oncology team manages this easily by lowering the abemaciclib dose and monitoring you; don't adjust anything yourself. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abemaciclib and Itraconazole 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 Itraconazole interaction managed?
What your care team may do: Lower your abemaciclib dose while you are on itraconazole (for example, from 200 or 150 mg twice daily down to 100 mg twice daily, and if you were already at 100 mg twice daily for side effects, down to 50 mg twice daily). Watch you more closely for side effects like diarrhea, low blood counts, or fatigue. Raise your dose back to your usual amount a few days after the i… 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.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Abemaciclib or Itraconazole 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 Itraconazole
Keep reading about Abemaciclib
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:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist