Mavacamten and Abemaciclib: 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
Mavacamten
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. Mavacamten (Camzyos) is your heart medication, and abemaciclib (Verzenio) is a cancer medication. Your body uses a liver enzyme called CYP3A4 to break down abemaciclib. Mavacamten can speed that enzyme up a bit, which means your body may clear abemaciclib a little faster than usual.
In plain terms, this could lower how much abemaciclib is working in your body, which matters for a cancer treatment. The good news is this is a mild, mostly theoretical concern, and your care team can handle it by keeping a closer eye on how you're doing and adjusting things if needed. Please don't change either medicine on your own, just mention this to your pharmacist or doctor.
Mechanism: Mavacamten is a moderate CYP3A4 inducer. Abemaciclib is a CYP3A4 substrate, so induction may increase its metabolism and reduce exposure (AUC/Cmax), potentially lowering antineoplastic efficacy.
- Direction: reduced abemaciclib exposure and possibly reduced efficacy.
- Magnitude: Extrapolated from midazolam data (AUC down ~13-45%, Cmax down ~7-24% depending on mavacamten dose); no abemaciclib-specific data.
- Onset: unspecified; enzyme induction is typically gradual.
- Evidence: theoretical.
Management: Monitor oncologic response closely. Abemaciclib dosing may need individualization by the oncology team; consider therapeutic-response assessment if efficacy appears diminished.
What happens
Reduced CYP3A4 substrate exposure and reduced efficacy of CYP3A4 substrate
Interaction Deep Dive
When mavacamten is given alongside CYP3A4 substrates, exposure to those substrates may fall, which could in turn diminish their effectiveness. For this reason, careful monitoring is warranted whenever mavacamten is combined with CYP3A4 substrates. A drug interaction study in healthy subjects showed that a 16 day regimen of mavacamten (25 mg on days 1 and 2, then 15 mg over the following 14 days) lowered the AUC(inf) of midazolam by 13% and its Cmax by 7%. In symptomatic obstructive hypertrophic cardiomyopathy (HCM) patients receiving once daily mavacamten dosing at the upper end of the therapeutic range, midazolam AUC(inf) and Cmax are projected to fall by as much as 45% and 24%, respectively1.
Why it happens (mechanism)
Induction of CYP3A4-substrate metabolism by mavacamten
How to manage this interaction
What your care team may do:
- Keep monitoring how well your cancer treatment is working, since abemaciclib levels could run a bit lower.
- Adjust and individualize your abemaciclib dose if your team feels it's needed, based on how you respond.
- Consider an alternative if response seems reduced.
What you should do:
- Keep taking both medicines exactly as prescribed.
- Tell your pharmacist and oncologist that you take both, so they can watch for any drop in effectiveness.
- Report any concerns or changes in how you feel.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In a study of drug interactions, giving a 16 day regimen of mavacamten (25 mg on days 1 and 2, then 15 mg for 14 days) alongside midazolam lowered midazolam's AUC(inf) by 13% and Cmax by 7% in healthy participants. When mavacamten is given once daily to symptomatic obstructive hypertrophic cardiomyopathy (HCM) patients at the upper limit of the therapeutic range, midazolam AUC(inf) and Cmax are projected to fall by as much as 45% and 24%, respectively 1.
Common questions
Can I take Mavacamten and Abemaciclib together?
Mavacamten may speed up how your body clears abemaciclib, which could make the cancer drug slightly less effective. Keep taking both as prescribed and let your care team monitor and adjust as needed. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Mavacamten and Abemaciclib 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 Mavacamten and Abemaciclib interaction managed?
What your care team may do: Keep monitoring how well your cancer treatment is working, since abemaciclib levels could run a bit lower. Adjust and individualize your abemaciclib dose if your team feels it's needed, based on how you respond. Consider an alternative if response seems reduced. What you should do: Keep taking both medicines exactly as prescribed. Tell your pharmacist and oncologist tha… 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 Mavacamten or Abemaciclib 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: CAMZYOS(R) oral capsules, mavacamten oral capsules. Bristol-Myers Squibb Company (per Manufacturer), Princeton, NJ, 2025. DailyMed
Keep reading about Mavacamten
Keep reading about Abemaciclib
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major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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