Abemaciclib and Boceprevir: 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
Boceprevir
No brand names on recordAbemaciclib
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. Abemaciclib (Verzenio) is broken down in your body by a liver enzyme called CYP3A4. Boceprevir slows that enzyme down. When the enzyme is slowed, your abemaciclib clears out more slowly and can build up higher than intended.
Because abemaciclib is a cancer medicine, higher levels can mean more side effects, like diarrhea, nausea, tiredness, or a drop in blood counts. The good news is this is very manageable. Your care team can lower your abemaciclib dose while you're on boceprevir and watch you a little more closely. Please don't change anything on your own, just check with your oncologist or pharmacist so they can tailor the plan for you.
Mechanism: Boceprevir is a strong CYP3A4 inhibitor. Abemaciclib is a CYP3A4 substrate (not a prodrug), so inhibition reduces its metabolism and increases plasma exposure of abemaciclib and its active metabolites, raising toxicity risk.
- Direction: increased abemaciclib exposure (AUC/Cmax).
- Evidence: theoretical; severity: moderate; 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, reduce further to 50 mg BID.
- On discontinuing the inhibitor, resume the pre-inhibitor dose after 3 to 5 half-lives of boceprevir.
- Monitor for GI toxicity, myelosuppression, hepatotoxicity, and VTE.
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 increasing 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 because of adverse reactions, reduce abemaciclib further to 50 mg twice daily. Once the strong CYP3A inhibitor is stopped, raise the abemaciclib dose (allowing 3-5 half-lives of the inhibitor to elapse) back to the dose used prior to starting the strong inhibitor1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated abemaciclib metabolism
How to manage this interaction
Keep taking both medicines as prescribed unless your care team tells you otherwise. This combination can be managed, mainly by adjusting your abemaciclib dose and watching you more closely.
- Your team may lower your abemaciclib dose while you are on boceprevir (for example, to 100 mg twice daily, or 50 mg twice daily if you've already been reduced for side effects).
- When boceprevir is stopped, your team can raise abemaciclib back to your previous dose after enough time has passed for the boceprevir to clear.
- Report side effects like diarrhea, nausea, unusual tiredness, fever, or signs of low blood counts to your oncologist or pharmacist.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) In drug interaction studies, taking 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, giving 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 Boceprevir together?
Boceprevir can raise abemaciclib levels and side effects, so your oncology team will likely reduce the abemaciclib dose and monitor you more closely while the two are used together. Don't adjust anything yourself; check with your prescriber or pharmacist. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abemaciclib and Boceprevir 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 Boceprevir interaction managed?
Keep taking both medicines as prescribed unless your care team tells you otherwise. This combination can be managed, mainly by adjusting your abemaciclib dose and watching you more closely. Your team may lower your abemaciclib dose while you are on boceprevir (for example, to 100 mg twice daily, or 50 mg twice daily if you've already been reduced for side effects). When boceprevir is stopped, your… 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 Boceprevir 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 Boceprevir
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