Tacrolimus 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
Tacrolimus
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.
Here's what's going on. Tacrolimus (Prograf, Envarsus, Astagraf) is an anti-rejection medicine that your body normally pushes out using a transporter called P-gp. Belumosudil (Rezurock) slows that transporter down. When you take them together, less tacrolimus gets moved out, so more of it can build up in your blood.
Tacrolimus is a drug where even small increases can matter, so higher levels can mean more side effects like kidney strain, tremor, high blood pressure, or high blood sugar. The good news is your care team knows how to handle this by checking your tacrolimus levels and adjusting your dose as needed. Please don't change anything on your own, just talk with your pharmacist or doctor.
Mechanism: Belumosudil inhibits P-gp-mediated efflux; tacrolimus is a P-gp (and CYP3A4) substrate with a narrow therapeutic index. Neither is a prodrug here, so inhibition raises tacrolimus exposure.
Direction/magnitude: Increased P-gp substrate exposure. In a dedicated study, belumosudil roughly doubled dabigatran Cmax and AUC; a comparable rise in tacrolimus exposure is plausible.
- Evidence: probable; onset: unspecified; severity: major.
- Management: Avoid the combination when possible. If unavoidable, reduce tacrolimus dose as needed and intensify therapeutic drug monitoring (trough levels), renal function, BP, glucose, and neurotoxicity signs.
What happens
Increased P-gp substrate exposure
Interaction Deep Dive
Do not give belumosudil (a P-gp inhibitor) together with a P-gp substrate that has a narrow therapeutic index (NTI), since even small shifts in concentration could produce serious toxicities. When such combined use is unavoidable, reduce the dose of the P-gp substrate as needed. One drug interaction study found that giving belumosudil alongside dabigatran (a P-gp substrate) raised dabigatran Cmax and AUC 2-fold1.
Why it happens (mechanism)
Inhibition of P-gp-mediated efflux transport by belumosudil
How to manage this interaction
Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. This combination can raise tacrolimus levels, and your team can manage that safely.
- Your prescriber may check your tacrolimus blood levels more closely.
- Your tacrolimus dose may need to be adjusted and individualized by your care team based on those levels.
- In some cases the team may consider whether an alternative is appropriate.
What to do: Tell your pharmacist and doctor you take both. Report new tremor, headache, reduced urination, swelling, or unusually high blood sugar so they can respond quickly.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In a study evaluating drug interactions, giving belumosudil together with dabigatran (a P-gp substrate) raised the Cmax and AUC of dabigatran by 2-fold 1.
Common questions
Can I take Tacrolimus and Belumosudil together?
Belumosudil can raise tacrolimus levels by slowing the P-gp transporter, and because tacrolimus has a narrow safety margin, expect closer blood-level monitoring and possible dose adjustment. Don't change your doses yourself; let your care team manage it. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Tacrolimus and Belumosudil 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 Tacrolimus and Belumosudil interaction managed?
Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. This combination can raise tacrolimus levels, and your team can manage that safely. Your prescriber may check your tacrolimus blood levels more closely. Your tacrolimus dose may need to be adjusted and individualized by your care team based on those levels. In some cases the team may consider whether an alt… 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.
Questions for your pharmacist
- Does my dose of Tacrolimus 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 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 Tacrolimus
Keep reading about Belumosudil
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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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