Mavacamten and Belumosudil: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 15, 2026 · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Mavacamten
Belumosudil
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.
You've been prescribed mavacamten (Camzyos) for your heart along with belumosudil (Rezurock). Here's the simple picture: mavacamten can speed up the liver enzyme that breaks down belumosudil. When that happens, your body may clear belumosudil a little faster, which could make it slightly less effective.
The good news is this concern is mostly based on how these drugs work in theory, not strong real-world reports, and the expected change is small. Please keep taking both exactly as prescribed. Your care team can watch how well the belumosudil is working and adjust things if needed, so this is very manageable.
Mechanism: Mavacamten is a weak CYP3A4 inducer. Belumosudil is partly a CYP3A4 substrate, so induction may increase its clearance and lower systemic exposure (AUC/Cmax), potentially reducing efficacy. Neither drug is a prodrug, so the effect is a straightforward loss of exposure.
- Direction: reduced belumosudil exposure and possible reduced efficacy
- Magnitude: modest; midazolam probe showed AUC decrease up to ~45% and Cmax up to ~24% at upper therapeutic mavacamten range
- Evidence: theoretical / PK-model based
- Onset: unspecified
Management: Continue both as prescribed; monitor belumosudil clinical response and individualize dosing if response appears inadequate.
What happens
Reduced CYP3A4 substrate exposure and reduced efficacy of CYP3A4 substrate
Interaction Deep Dive
When mavacamten is given together with CYP3A4 substrates, the exposure to those substrates may fall, potentially diminishing their effectiveness as well. For this reason, careful monitoring is warranted whenever mavacamten and CYP3A4 substrates are used at the same time. 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 for 14 days) lowered the AUC(inf) and Cmax of midazolam by 13% and 7%, respectively. In symptomatic obstructive hypertrophic cardiomyopathy (HCM) patients receiving once daily mavacamten 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 you on both medications, since this interaction is theoretical and the expected change is small.
- Monitor how well belumosudil is controlling your condition.
- Adjust and individualize the belumosudil dose if your team feels your response could be stronger.
What you can do:
- Take both drugs exactly as prescribed. Do not start, stop, or change doses on your own.
- Tell your pharmacist or prescriber if your symptoms seem to be returning or not well controlled.
- Keep a current list of all your medications so your team can check for other CYP3A4 concerns.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In a drug interaction trial, giving a 16 day regimen of mavacamten (25 mg on days 1 and 2, then 15 mg for 14 days) together with midazolam reduced midazolam AUC(inf) by 13% and Cmax by 7% in healthy subjects. When mavacamten is given once daily to symptomatic obstructive hypertrophic cardiomyopathy (HCM) patients at the upper end 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 Belumosudil together?
Mavacamten may slightly lower belumosudil levels and could make it a bit less effective, but this is theoretical and manageable. Keep taking both as prescribed and let your care team monitor how well the belumosudil is working. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Mavacamten and Belumosudil 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 Belumosudil interaction managed?
What your care team may do: Keep you on both medications, since this interaction is theoretical and the expected change is small. Monitor how well belumosudil is controlling your condition. Adjust and individualize the belumosudil dose if your team feels your response could be stronger. What you can do: Take both drugs exactly as prescribed. Do not start, stop, or change doses on your own. Tell yo… 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 Belumosudil 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 Belumosudil
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.
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