Belumosudil and Haloperidol: 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
Haloperidol
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.
Here's what's going on. Belumosudil (Rezurock) can slow down the liver enzyme that breaks down your haloperidol. When that enzyme is slowed, more haloperidol can build up in your body than usual. That means you could feel stronger side effects, like drowsiness, stiffness, or restlessness. One that we watch closely is a change in your heart's rhythm (called QTc prolongation).
The good news is that this is very manageable. Your care team can keep an eye on how you're doing and adjust your haloperidol dose if needed. Please don't stop or change either medicine on your own. Just let your doctor or pharmacist know you take both so they can watch out for you.
Mechanism: Belumosudil inhibits CYP3A4, reducing metabolism of haloperidol (a CYP3A substrate), leading to increased haloperidol exposure. Neither agent is activated by this pathway, so effect and toxicity increase.
Clinical concern: Elevated haloperidol levels raise the risk of dose-dependent adverse effects, notably QTc prolongation (observed with the strong inhibitor ketoconazole), plus EPS and sedation.
- Direction: increased haloperidol effect
- Severity: major; Evidence: probable; Onset: unspecified
- Management: monitor for enhanced/prolonged haloperidol effects, obtain ECG for QTc, and reduce haloperidol dose if necessary.
What happens
Increased haloperidol exposure and an increased risk of haloperidol-related adverse events, including QTc interval prolongation
Interaction Deep Dive
When haloperidol (a CYP3A substrate) is taken together with inhibitors of CYP3A4, haloperidol levels can rise, potentially heightening adverse effects tied to haloperidol, such as prolongation of the QTc interval. A lengthening of QTc has been documented with concurrent administration of haloperidol and ketoconazole (a CYP3A4 inhibitor). Should combined use be necessary, watch for indications of intensified or extended pharmacologic effects from haloperidol and lower the haloperidol dose as needed1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of haloperidol
How to manage this interaction
What your care team may do:
- Keep both medicines if they are needed, and tailor your haloperidol dose to you (the dose may be lowered if signs of too much haloperidol appear).
- Monitor you more closely for stronger or longer-lasting haloperidol effects such as sedation, muscle stiffness, or restlessness.
- Check your heart rhythm (an ECG) since haloperidol can affect the QTc interval.
What you can do: Keep taking both exactly as prescribed. Tell your pharmacist or prescriber that you take these together, and report any fainting, palpitations, dizziness, or unusual drowsiness or stiffness promptly.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
3 reports — tap to read
a) A prolongation of QTc was noted when haloperidol was co-administered with ketoconazole (a CYP3A4 inhibitor) at 400 mg/day 1.
b) The influence of nefazodone on the pharmacokinetics and pharmacodynamics of haloperidol was investigated in 12 healthy male patients. Nefazodone 200 mg administered every 12 hours produced a minor effect on the pharmacokinetics of a single 5 mg dose of haloperidol. The mean AUC, peak concentration, and 12-hour concentration of haloperidol rose by 36%, 13%, and 37%, respectively. The effect on the AUC was the only one that achieved statistical significance. Nefazodone did not consistently affect the pharmacodynamics of haloperidol 2.
c) When a single dose of haloperidol was given together with steady-state nefazodone, haloperidol clearance was reduced. The pharmacodynamic effects of haloperidol were not significantly changed 3.
Common questions
Can I take Belumosudil and Haloperidol together?
Belumosudil can raise haloperidol levels, increasing side effects including heart-rhythm (QTc) changes; keep taking both as prescribed while your care team monitors you and adjusts your haloperidol dose if needed. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Belumosudil and Haloperidol 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 Haloperidol interaction managed?
What your care team may do: Keep both medicines if they are needed, and tailor your haloperidol dose to you (the dose may be lowered if signs of too much haloperidol appear). Monitor you more closely for stronger or longer-lasting haloperidol effects such as sedation, muscle stiffness, or restlessness. Check your heart rhythm (an ECG) since haloperidol can affect the QTc interval. What you can do:… 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 Belumosudil or Haloperidol 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 (3)
- Product Information: HALDOL(R) Decanoate 100 intramuscular injection, haloperidol decanoate intramuscular injection. Janssen Pharmaceuticals Inc (per FDA), Titusville, NJ, 2025.
- Barbhaiya RH, Shukla UA, Greene DS, et al: Investigation of pharmacokinetic and pharmacodynamic interactions after coadministration of nefazodone and haloperidol. J Clin Psychopharmacol 1996; 16:26-34. PubMed
- DeVane CL: Nefazodone--pharmacology and efficacy of a new antidepressant agent: formulary considerations. P and T 1995; 20:363-374.
Keep reading about Haloperidol
Keep reading about Belumosudil
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