Abemaciclib and Verapamil: 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
Verapamil
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. Verapamil (a heart and blood pressure medicine) can slow down the liver enzyme that breaks down abemaciclib (Verzenio), your cancer medicine. When that enzyme works more slowly, more abemaciclib can build up in your body.
That higher level can mean more side effects, like diarrhea, tiredness, or a drop in blood cell counts. The good news is this is very manageable. Your care team can watch you a little more closely and adjust your abemaciclib dose if needed. Please don't stop or change either medicine on your own. Just let your pharmacist or doctor know you take both so they can keep you safe.
Mechanism: Verapamil is a moderate CYP3A4 inhibitor; abemaciclib is a CYP3A4 substrate (not a prodrug). Inhibition reduces metabolic clearance, increasing plasma exposure of abemaciclib and its active metabolites, raising toxicity risk.
- Direction: Increased abemaciclib exposure (AUC/Cmax).
- Evidence: Theoretical; onset unspecified.
- Severity: Moderate.
Management: Monitor for adverse reactions (diarrhea, hepatotoxicity, neutropenia, venous thromboembolism). If coadministered, consider reducing abemaciclib in 50 mg increments per labeling (e.g., 150 mg BID to 100 mg BID, then 50 mg BID; discontinue if 50 mg BID not tolerated). Individualize based on tolerability.
What happens
Increased abemaciclib plasma concentration
Interaction Deep Dive
When abemaciclib (which is metabolized by CYP3A4) is taken together with a moderate CYP3A4 inhibitor, plasma concentrations of both abemaciclib and its active metabolite can rise, potentially increasing toxicity. Should the two be given together, watch for adverse reactions and think about lowering the abemaciclib dose by 50-mg steps. For patients on 150 mg twice daily, the first reduction is to 100 mg twice daily and the second to 50 mg twice daily, with the drug discontinued if 50 mg twice daily cannot be tolerated. For patients on 200 mg twice daily, the first reduction is to 150 mg twice daily, the second to 100 mg twice daily, and the third to 50 mg twice daily, discontinuing use if 50 mg twice daily is not tolerated1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated abemaciclib metabolism
How to manage this interaction
The takeaway: this pairing is manageable with a little extra attention from your care team.
- Keep taking both exactly as prescribed unless your doctor tells you otherwise.
- Your team may monitor you more closely for side effects like diarrhea, fatigue, or changes in blood counts.
- If needed, your abemaciclib dose may be adjusted and individualized (often reduced in 50 mg steps) by your care team.
- Tell your pharmacist or oncologist that you take both, and report any new or worsening side effects promptly.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In drug interaction studies, taking abemaciclib together with verapamil and diltiazem (both moderate CYP3A inhibitors) is projected to raise the AUC of abemaciclib along with its active metabolites (M2, M18, and M20) by roughly 1.6-fold and 2.4-fold, respectively 1.
Common questions
Can I take Abemaciclib and Verapamil together?
Verapamil can raise abemaciclib levels and side effects; keep taking both as prescribed and let your oncology team monitor you and adjust the abemaciclib dose if needed. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abemaciclib and Verapamil 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 Verapamil interaction managed?
The takeaway: this pairing is manageable with a little extra attention from your care team. Keep taking both exactly as prescribed unless your doctor tells you otherwise. Your team may monitor you more closely for side effects like diarrhea, fatigue, or changes in blood counts. If needed, your abemaciclib dose may be adjusted and individualized (often reduced in 50 mg steps) by your care team. Tel… 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 Verapamil 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, 2018. DailyMed
Keep reading about Verapamil
Keep reading about Abemaciclib
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