Abemaciclib and Dronedarone: 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
Dronedarone
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.
Let's talk about taking dronedarone (Multaq) with abemaciclib (Verzenio) together. Dronedarone can slow down the liver enzyme that clears abemaciclib out of your body. When that happens, more abemaciclib can build up in your blood, which may lead to stronger side effects like diarrhea, nausea, tiredness, or lower blood counts.
This concern is based mostly on how these drugs are expected to behave, not on strong studies, so please don't worry. The good news is that your care team can manage this easily by watching how you feel and, if needed, adjusting your abemaciclib dose. Never change either medicine on your own, just check in with your pharmacist or oncologist.
Effect: Increased abemaciclib exposure (parent drug and active metabolite) with concurrent dronedarone.
Mechanism: Dronedarone is a moderate CYP3A4 inhibitor; abemaciclib is a CYP3A4 substrate. Inhibition reduces metabolism, raising AUC/Cmax and potential toxicity (diarrhea, neutropenia, hepatotoxicity, fatigue).
Evidence: Theoretical; severity moderate; onset unspecified.
Management:
- Monitor for adverse reactions if coadministered.
- Consider dose reduction in 50-mg increments per labeling (e.g., 150 mg BID to 100 mg BID to 50 mg BID; 200 mg BID stepping down similarly).
- Discontinue if 50 mg BID is 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, the plasma concentrations of abemaciclib along with its active metabolite may rise, which can increase the risk of toxicity. In cases of coadministration, watch for adverse reactions and consider lowering the abemaciclib dose in 50-mg steps. For patients taking 150 mg twice daily, the first reduction is to 100 mg twice daily, followed by a second reduction to 50 mg twice daily, and use should be discontinued if 50 mg twice daily is not 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, with discontinuation if 50 mg twice daily is not tolerated1.
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. Here is how a team typically handles this combination:
- They may monitor you more closely for side effects such as diarrhea, nausea, fatigue, or signs of low blood counts.
- Your abemaciclib dose may be adjusted and individualized, usually lowered in 50-mg steps if needed.
- They may run bloodwork to check how you are tolerating treatment.
Let your pharmacist or oncologist know if you notice new or worsening side effects, and tell any provider about both drugs before starting anything new.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) Drug interaction studies predict that giving abemaciclib together with verapamil and diltiazem (both moderate CYP3A inhibitors) will 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 Dronedarone together?
Dronedarone can raise abemaciclib levels and increase the chance of side effects; your care team can manage this by watching for symptoms and adjusting the abemaciclib dose if needed. Keep taking both as prescribed and report any new side effects. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abemaciclib and Dronedarone 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 Dronedarone interaction managed?
Keep taking both medicines as prescribed unless your care team tells you otherwise. Here is how a team typically handles this combination: They may monitor you more closely for side effects such as diarrhea, nausea, fatigue, or signs of low blood counts. Your abemaciclib dose may be adjusted and individualized, usually lowered in 50-mg steps if needed. They may run bloodwork to check how you are t… 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 Dronedarone 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 Dronedarone
Keep reading about Abemaciclib
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