Itraconazole 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
Itraconazole
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. Belumosudil (Rezurock) is broken down in your body by a liver enzyme called CYP3A4. Itraconazole (Sporanox) is a strong blocker of that same enzyme. When you take them together, itraconazole slows down how fast your body clears belumosudil, so more of it can build up in your blood.
That means you could feel belumosudil's side effects more strongly, like nausea, tiredness, or other reactions. The good news is this is very manageable. Your care team can watch you a little more closely and adjust your belumosudil dose if needed. Please don't stop or change either medicine on your own, just check in with your pharmacist or doctor.
Mechanism: Itraconazole is a potent CYP3A4 inhibitor; belumosudil is a CYP3A4 substrate (not a prodrug). Inhibition of belumosudil metabolism increases its systemic exposure (AUC/Cmax).
Direction/effect: Increased belumosudil plasma concentrations and greater risk of substrate-related adverse effects.
- Evidence: Theoretical, based on known CYP3A4 pharmacology.
- Onset: Unspecified.
- Severity: Major.
Management: Monitor for belumosudil-related adverse reactions. Belumosudil dose may need to be reduced and individualized when co-administered with a strong CYP3A4 inhibitor. Consult current prescribing information for strong-inhibitor dosing guidance.
What happens
Increased CYP3A4 substrate exposure and an increased risk of CYP3A4 substrate-related adverse effects
Interaction Deep Dive
Giving itraconazole (a strong inhibitor of CYP3A4) alongside substrates of CYP3A4 can raise the plasma levels of those substrates, which may lead to a greater incidence of adverse reactions from them. Watch for adverse reactions. It may be necessary to lower the dose of the concomitant drug12.
Why it happens (mechanism)
Inhibition of CYP3A4-substrate metabolism by itraconazole
How to manage this interaction
What your care team may do:
- Keep taking both medicines exactly as prescribed unless told otherwise.
- Monitor you more closely for belumosudil side effects (such as nausea, fatigue, or other reactions).
- Adjust and individualize your belumosudil dose if needed while you are on itraconazole.
What you can do: Let your pharmacist or prescriber know you are taking both drugs. Report any new or worsening side effects. Do not stop, start, or change the dose of either medicine on your own, your care team can tailor this safely.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Itraconazole and Belumosudil together?
Itraconazole can raise belumosudil levels and make its side effects more likely, so your care team may monitor you more closely and adjust your belumosudil dose. Keep taking both as prescribed and report any new side effects. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Itraconazole 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 Itraconazole and Belumosudil interaction managed?
What your care team may do: Keep taking both medicines exactly as prescribed unless told otherwise. Monitor you more closely for belumosudil side effects (such as nausea, fatigue, or other reactions). Adjust and individualize your belumosudil dose if needed while you are on itraconazole. What you can do: Let your pharmacist or prescriber know you are taking both drugs. Report any new or worsening… 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 Itraconazole 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 (2)
Keep reading about Itraconazole
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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