Belumosudil and Mifepristone: 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
Mifepristone
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.
These two medicines can push each other's levels up in your body. Mifepristone slows down a liver enzyme (called CYP3A4) that helps break down belumosudil. When that enzyme is slowed, belumosudil can build up, which may raise the chance of side effects.
At the same time, belumosudil can also slow the breakdown of mifepristone, so mifepristone levels can rise too. This concern is mostly based on how the drugs work, not on lots of real-world reports. The good news is your care team can manage this by choosing the right doses and keeping a closer eye on you. Please don't change anything on your own, just check with your doctor or pharmacist.
Direction: Bidirectional exposure increase. Mifepristone is a strong CYP3A4 inhibitor and will likely raise belumosudil (a CYP3A4 substrate) AUC/Cmax. Belumosudil, itself a CYP3A4 substrate, is metabolized by the same pathway mifepristone inhibits, and mifepristone (also a CYP3A4 substrate) can accumulate if CYP3A4 is inhibited.
- Mechanism: Inhibition of CYP3A4-mediated metabolism.
- Evidence: Theoretical; magnitude and onset unspecified.
- Severity: Major.
- Management: Use lowest effective dose/decreased frequency; limit mifepristone to 900 mg; prefer alternatives lacking these CYP3A4 characteristics; therapeutic monitoring for toxicity. Allow at least 2 weeks after stopping mifepristone before starting CYP3A4 inhibitors/substrates.
What happens
Increased CYP3A4 substrate exposure and an increased miFEPRIStone exposure
Interaction Deep Dive
Because miFEPRIStone acts as a potent inhibitor of CYP3A4, extreme caution is warranted when it is given together with agents that undergo extensive first pass metabolism through CYP3A4, since exposure to those CYP3A4 substrates may rise. Employ the smallest possible dose and/or reduce the dosing frequency while conducting therapeutic monitoring. Where feasible, opt for alternative medications that lack these metabolic properties. Furthermore, miFEPRIStone itself is a CYP3A4 substrate, so its exposure may increase when it is taken alongside CYP3A4 inhibitors. The benefits of using these agents together should be carefully balanced against the possible risks. Restrict the miFEPRIStone dose to 900 mg. After discontinuing miFEPRIStone, allow a minimum of 2 weeks to elapse before starting CYP3A4 inhibitors or substrates1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism by miFEPRIStone; inhibition of CYP3A4-mediated metabolism of miFEPRIStone
How to manage this interaction
Your care team can handle this safely. Keep taking both medicines exactly as prescribed unless your prescriber tells you otherwise.
- Doses may be adjusted and individualized, often using the lowest effective dose or less frequent dosing.
- Mifepristone dosing is typically kept at or below 900 mg when used with a CYP3A4 substrate/inhibitor.
- Your team may monitor you more closely for side effects.
- An alternative medicine may be preferred when one is available.
- If mifepristone is stopped, at least 2 weeks may be allowed before starting related drugs.
Report any new or stronger side effects to your pharmacist or doctor.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In a pharmacokinetic study, giving a single oral dose of ALPRAZolam 1 mg together with miFEPRIStone 1200 mg once daily for 10 days in healthy subjects led to greater ALPRAZolam (CYP3A4 inhibitor) exposure. Relative to ALPRAZolam given by itself, its coadministration with miFEPRIStone produced geometric mean ratios for AUC and Cmax of 1.8 and 0.81, respectively, for ALPRAZolam, and 0.76 and 0.39, respectively, for the 4-hydroxy-ALPRAZolam metabolite 1.
Common questions
Can I take Belumosudil and Mifepristone together?
Mifepristone and belumosudil can each raise the other's blood levels through CYP3A4, so your care team may lower doses, cap mifepristone at 900 mg, and monitor you more closely. 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 Belumosudil and Mifepristone 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 Mifepristone interaction managed?
Your care team can handle this safely. Keep taking both medicines exactly as prescribed unless your prescriber tells you otherwise. Doses may be adjusted and individualized, often using the lowest effective dose or less frequent dosing. Mifepristone dosing is typically kept at or below 900 mg when used with a CYP3A4 substrate/inhibitor. Your team may monitor you more closely for side effects. An a… 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.
Questions for your pharmacist
- Does my dose of Belumosudil or Mifepristone 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: KORLYM(R) oral tablets, mifepristone oral tablets. Corcept Therapeutics Incorporated (per Dailmed), Redwood City, CA, 2024. DailyMed
Keep reading about Mifepristone
Keep reading about Belumosudil
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