Belumosudil and Carbamazepine: 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
Carbamazepine
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 belumosudil (Rezurock), which helps treat chronic graft-versus-host disease, along with carbamazepine (Tegretol), a seizure and mood medicine. Here's what's going on: carbamazepine speeds up the liver enzyme that breaks down belumosudil. That means your body clears belumosudil faster, so there's less of it in your blood to do its job.
The concern here isn't a dangerous side effect. It's that belumosudil may simply not work as well. The good news is this is very manageable. Your care team can adjust your belumosudil dose to make up the difference, so don't change anything on your own. Just talk with your doctor or pharmacist so they can tailor your plan.
Effect: Carbamazepine (strong CYP3A inducer) increases metabolism of belumosudil (CYP3A substrate), reducing belumosudil exposure and potentially its efficacy. Neither is a prodrug, so induction straightforwardly lowers active drug levels.
- Magnitude: With rifampin (strong CYP3A inducer), belumosudil Cmax fell 59% and AUC fell 72%.
- Direction: Reduced belumosudil effect (treatment failure risk).
- Evidence/onset: Probable; onset unspecified (induction develops over days to weeks).
- Management: Increase belumosudil to 200 mg twice daily when coadministered with a strong CYP3A inducer. Monitor clinical response.
What happens
Reduced belumosudil exposure and reduced efficacy of belumosudil
Interaction Deep Dive
When belumosudil (a CYP3A substrate) is given together with a strong CYP3A inducer, belumosudil exposure may fall, potentially diminishing its effectiveness. A drug interaction study conducted in healthy subjects found that giving belumosudil alongside rifAMPin (a strong CYP3A inducer) lowered belumosudil Cmax by 59% and AUC by 72%. When belumosudil is combined with a strong CYP3A inducer, raise the belumosudil dose to 200 mg twice daily1.
Why it happens (mechanism)
Induction of CYP3A-mediated belumosudil metabolism
How to manage this interaction
This interaction is manageable and is expected mainly to weaken belumosudil's effect, not to cause a new toxicity.
- Keep taking both exactly as prescribed unless your care team tells you otherwise.
- Your team may increase your belumosudil dose (the labeled adjustment is to 200 mg twice daily when taken with a strong CYP3A inducer like carbamazepine).
- They may also watch your response more closely to make sure belumosudil is still working.
What to do: Tell your pharmacist and prescriber that you take both drugs so they can adjust and individualize your plan.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In a drug interaction study conducted in healthy subjects, giving belumosudil together with rifAMPin (a strong CYP3A inducer) reduced the Cmax of belumosudil by 59% and the AUC by 72% 1.
Common questions
Can I take Belumosudil and Carbamazepine together?
Carbamazepine can lower belumosudil levels and make it work less well; your care team may raise your belumosudil dose (to 200 mg twice daily) and watch how you respond, so keep taking both as prescribed and check in with them. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Belumosudil and Carbamazepine interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Belumosudil and Carbamazepine interaction managed?
This interaction is manageable and is expected mainly to weaken belumosudil's effect, not to cause a new toxicity. Keep taking both exactly as prescribed unless your care team tells you otherwise. Your team may increase your belumosudil dose (the labeled adjustment is to 200 mg twice daily when taken with a strong CYP3A inducer like carbamazepine). They may also watch your response more closely to… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Belumosudil or Carbamazepine 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 a safer alternative to one of these medications for me?
References (1)
- Product Information: REZUROCK(R) oral tablets, belumosudil oral tablets. Kadmon Pharmaceuticals LLC (per FDA), Bridgewater, NJ, 2024. DailyMed
Keep reading about Carbamazepine
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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