Abemaciclib and Imatinib: 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
Imatinib
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.
These two cancer medicines can interact. Imatinib slows down a liver enzyme (called CYP3A4) that normally helps clear abemaciclib out of your body. When abemaciclib is cleared more slowly, its level in your blood can rise, and higher levels can mean more side effects, like diarrhea, low blood counts, tiredness, or nausea.
I want to reassure you that this is very manageable. Your cancer team knows about this and can watch you more closely and, if needed, fine-tune your abemaciclib dose. Please keep taking both medicines exactly as prescribed, and let your pharmacist or doctor know if you notice new or worsening side effects.
Effect: Increased abemaciclib exposure (parent drug and active metabolite) with potential for enhanced toxicity.
Mechanism: Imatinib is a moderate CYP3A4 inhibitor; abemaciclib is a CYP3A4 substrate. Inhibition reduces abemaciclib clearance, raising AUC/Cmax. Neither is a prodrug in this context, so the direction is increased active drug effect.
Evidence/Onset: Theoretical; onset unspecified.
Management:
- Monitor for adverse reactions (diarrhea, cytopenias, hepatotoxicity, fatigue).
- Consider dose reduction in 50-mg increments: 150 mg BID to 100 to 50; 200 mg BID to 150 to 100 to 50; discontinue if 50 mg BID not tolerated.
What happens
Increased abemaciclib plasma concentration
Interaction Deep Dive
When abemaciclib, which is a CYP3A4 substrate, is taken together with a moderate CYP3A4 inhibitor, plasma concentrations of 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 in 50-mg steps. For those on 150 mg twice daily, the first reduction is to 100 mg twice daily and the second to 50 mg twice daily, with discontinuation if 50 mg twice daily cannot be tolerated. For those 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, again discontinuing if 50 mg twice daily is not tolerated1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated abemaciclib metabolism
How to manage this interaction
The good news: your care team can manage this by tailoring your dose and watching you more closely.
- Keep taking both medicines as prescribed unless your prescriber tells you otherwise.
- Your team may monitor you more closely for side effects such as diarrhea, low blood counts, fatigue, or liver changes.
- If needed, your doctor may reduce the abemaciclib dose in 50-mg steps, individualized to how you tolerate it.
What to do: Report new or worsening side effects to your pharmacist or oncologist, and do not change your dose on your own.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In drug interaction studies, giving 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 Imatinib together?
Imatinib can raise abemaciclib levels and increase side effects, but your cancer team can manage this with closer monitoring and, if needed, a dose reduction. 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 Imatinib 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 Imatinib interaction managed?
The good news: your care team can manage this by tailoring your dose and watching you more closely. Keep taking both medicines as prescribed unless your prescriber tells you otherwise. Your team may monitor you more closely for side effects such as diarrhea, low blood counts, fatigue, or liver changes. If needed, your doctor may reduce the abemaciclib dose in 50-mg steps, individualized to how you… 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 Imatinib 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 Imatinib
Keep reading about Abemaciclib
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