Belumosudil and Clarithromycin: 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
Clarithromycin
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.
Let's talk about taking clarithromycin (an antibiotic) together with belumosudil (Rezurock, used for graft-versus-host disease). Your body clears belumosudil using a liver enzyme called CYP3A4. Clarithromycin slows that enzyme down, so belumosudil can build up in your blood higher than intended. That means more of the drug hanging around, which can raise your chance of side effects.
The good news is this is something your care team knows how to handle. They may adjust your belumosudil dose or keep a closer eye on you while you are on the antibiotic. Please don't change anything on your own, just check in with your pharmacist or doctor so they can plan it out.
Interaction: Clarithromycin is a strong CYP3A4 inhibitor; belumosudil is a CYP3A4 substrate. Coadministration is expected to reduce belumosudil clearance and increase its exposure (AUC/Cmax), raising toxicity risk.
- Direction: Increased belumosudil exposure (both are active drugs; not a prodrug scenario).
- Mechanism: Inhibition of CYP3A4-mediated belumosudil metabolism.
- Severity/Evidence: Major severity; evidence is theoretical. Onset unspecified.
- Management: Use caution. Consider belumosudil dose adjustment where possible and monitor closely for toxicity for the duration of concurrent therapy. Consider a non-CYP3A4-inhibiting antibiotic alternative if appropriate.
What happens
Increased exposure of CYP3A4 substrate and risk for toxicity
Interaction Deep Dive
Exercise caution when clarithromycin, which acts as a strong CYP3A4 inhibitor, is given together with drugs that undergo extensive CYP3A4 metabolism, since this combination can raise plasma levels of the CYP3A4 substrate and heighten the potential for toxicity12. Where feasible, dose adjustments should be considered, along with careful monitoring of serum concentrations for drugs that are chiefly metabolized by CYP3A41.
Why it happens (mechanism)
Inhibition of CYP3A4-substrate metabolism by clarithromycin
How to manage this interaction
You can keep taking both medications as prescribed, but this pairing is worth a conversation with your care team. Here is what they typically do:
- Adjust the dose: Your belumosudil dose may need to be adjusted and individualized by your care team while you are on clarithromycin.
- Monitor more closely: They may watch you more carefully for side effects during the combination.
- Consider alternatives: Sometimes a different antibiotic that does not affect this enzyme is an option.
Let your pharmacist or prescriber know you have been prescribed both, and report any new or worsening symptoms.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) In drug interaction studies, giving clarithromycin 500 mg every 8 hours together with omeprazole 40 mg daily to healthy adult subjects led to higher steady-state plasma concentrations of clarithromycin [with Cmax, AUC (0 to 24), and half-life rising by 30%, 89%, and 34%, respectively] 2.
b) Coadministration of omeprazole raised the plasma levels of clarithromycin and 14-OH clarithromycin. For clarithromycin, the mean Cmax was 10% higher, the mean Cmin was 27% higher, and the mean AUC (0 to 8) was 15% higher when clarithromycin was given with omeprazole compared with clarithromycin given by itself. Comparable findings were observed for 14-OH clarithromycin, with the mean Cmax 45% higher, the mean Cmin 57% higher, and the mean AUC (0 to 8) 45% higher 2.
Common questions
Can I take Belumosudil and Clarithromycin together?
Clarithromycin can raise belumosudil levels and side-effect risk by blocking the enzyme that clears it, so tell your care team about both drugs; they can adjust the dose or monitor you, or possibly choose a different antibiotic. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Belumosudil and Clarithromycin 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 Clarithromycin interaction managed?
You can keep taking both medications as prescribed, but this pairing is worth a conversation with your care team. Here is what they typically do: Adjust the dose: Your belumosudil dose may need to be adjusted and individualized by your care team while you are on clarithromycin. Monitor more closely: They may watch you more carefully for side effects during the combination. Consider alternatives: S… 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.
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 Clarithromycin 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 (2)
- Product Information: BIAXIN(R) XL Filmtab(R) oral extended-release tablets, clarithromycin oral extended-release tablets. AbbVie Inc (per FDA), North Chicago, IL, 2018. DailyMed
- Product Information: VOQUEZNA(R) TRIPLE PAK(R) oral kit, vonoprazan oral tablets, amoxicillin oral capsules, clarithromycin oral tablets kit. Phathom Pharmaceuticals (per FDA), Buffalo Grove, IL, 2024. DailyMed
Keep reading about Clarithromycin
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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