Belumosudil and Kratom: 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
Kratom
No brand names on recordBelumosudil
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.
What's going on: Belumosudil (Rezurock) is broken down in your body by a liver enzyme called CYP3A. Kratom appears to slow down that same enzyme. When the enzyme works more slowly, your belumosudil can build up higher than expected, which may mean more side effects such as nausea, tiredness, or other issues.
This tends to matter more with higher kratom doses or regular, ongoing use. The good news is your care team can manage this easily. Please don't stop or change either one on your own. Just let your pharmacist or doctor know if you take kratom so they can keep an eye on how you're doing.
Mechanism: Kratom is a probable CYP3A inhibitor; belumosudil is a CYP3A4 substrate. Inhibition reduces belumosudil metabolism, increasing its exposure (AUC/Cmax). Neither agent is a prodrug, so the effect is a straightforward rise in active belumosudil levels.
- Direction: increased belumosudil exposure and potential toxicity
- Magnitude: dose-dependent, greater with higher or chronic kratom use
- Onset: unspecified
- Evidence: probable
- Management: monitor for belumosudil-related adverse effects (hepatic labs, GI effects, fatigue, infection risk); dose may need individualized adjustment by the care team
What happens
Increased CYP3A substrate exposure
Interaction Deep Dive
Taking kratom (a CYP3A inhibitor) together with a CYP3A substrate may raise the exposure of that substrate, particularly when kratom is used at higher doses or over the long term1. Careful monitoring is advised2.
Why it happens (mechanism)
Inhibition of CYP3A-mediated metabolism by kratom
How to manage this interaction
Keep taking both as prescribed unless your care team tells you otherwise. Because kratom can raise belumosudil levels, here is what typically helps:
- Tell your pharmacist and prescriber that you use kratom, including how much and how often.
- Your team may monitor you more closely for belumosudil side effects and check labs.
- Your belumosudil dose may need to be adjusted and individualized by your care team.
- Report new or worsening symptoms (nausea, unusual tiredness, signs of infection) promptly.
The risk is greater with higher kratom doses or steady daily use, so consistency and honesty about your kratom use really help your team keep you safe.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) An open-label crossover study in healthy adults (N=12) assessed the intake of a single, low dose of kratom tea (2 g) combined with oral midazolam (a CYP3A probe substrate; 2.5 mg) and oral dextromethorphan (a CYP2D6 probe substrate; 30 mg). Kratom produced a modest rise in the geometric mean AUC of midazolam (1.39; 90% CI, 1.23 to 1.57) and its Cmax (1.5; 90% CI, 1.32 to 1.7); no impact on dextromethorphan AUC or Cmax was seen. The half life of midazolam was not significantly changed when kratom was taken concurrently, which points to inhibition of first-pass metabolism, mainly CYP3A within the intestine. The participants (median age, 30 years) had prior kratom exposure and agreed to refrain from concomitant medications and botanical or other natural products (including kratom) throughout the study 1.
Common questions
Can I take Belumosudil and Kratom together?
Kratom may slow the breakdown of belumosudil (Rezurock), raising its levels and side-effect risk, especially with higher or regular kratom use. Tell your pharmacist or doctor you use kratom so they can monitor you and adjust the dose if needed. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Belumosudil and Kratom 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 Belumosudil and Kratom interaction managed?
Keep taking both as prescribed unless your care team tells you otherwise. Because kratom can raise belumosudil levels, here is what typically helps: Tell your pharmacist and prescriber that you use kratom, including how much and how often. Your team may monitor you more closely for belumosudil side effects and check labs. Your belumosudil dose may need to be adjusted and individualized by your car… 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 Kratom 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 (2)
- Tanna RS, Nguyen JT, Hadi DL, et al: Clinical assessment of the drug interaction potential of the psychotropic natural product kratom. Clin Pharmacol Ther 2023; 113(6):1315-1325. PubMed
- Dhoble LR, Gour A, McCurdy CR, et al: Evaluating the drug interactions in kratom usage: clinical application. Expert Opin Drug Metab Toxicol 2025; 21(8):949-959. PubMed
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