Paclitaxel 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
Belumosudil
Paclitaxel
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 block a liver transporter called OATP1B1 that normally helps move certain drugs out of your body. Paclitaxel (Abraxane) is a strong chemotherapy drug, so if that transporter is slowed down, more paclitaxel could build up in your blood.
Higher levels of paclitaxel can mean more side effects, like low blood counts, nerve tingling or numbness, and feeling very tired. The good news is your cancer team knows how to handle this. They can adjust your dose and watch you more closely, so please keep taking both exactly as prescribed and talk with your oncologist or pharmacist before changing anything.
Mechanism: Belumosudil inhibits OATP1B1, reducing hepatic uptake/transport of OATP1B1 substrates and increasing their systemic exposure. Neither drug is a prodrug, so this is a straightforward exposure increase.
Direction/magnitude: Increased substrate exposure. In a clinical study, belumosudil raised rosuvastatin Cmax and AUC 3.6-fold and 4.6-fold. Paclitaxel is a cytotoxic with a narrow therapeutic margin, so elevated exposure risks additive myelosuppression, neuropathy, and other dose-limiting toxicities.
Evidence: Probable. Onset unspecified.
- Avoid concomitant use where feasible.
- If unavoidable, reduce paclitaxel dose as needed and individualize.
- Monitor CBC and for neuropathy/toxicity closely.
What happens
Increased OATP1B1 substrate exposure
Interaction Deep Dive
Do not give belumosudil (an OATP1B1 inhibitor) together with an OATP1B1 substrate that has a narrow therapeutic index (NTI), because even small changes in concentration could produce serious toxicities. When such combined use is unavoidable, lower the dose of the OATP1B1 substrate as necessary. A drug interaction study demonstrated that adding belumosudil raised the Cmax of rosuvastatin (a substrate of both OATP1B1 and BCRP) 3.6-fold and its AUC 4.6-fold1.
Why it happens (mechanism)
Inhibition of OATP1B1-mediated efflux transport by belumosudil
How to manage this interaction
What your care team may do:
- Try to avoid using these two together when another option exists.
- If both are needed, your paclitaxel dose may need to be adjusted and individualized by your oncology team.
- Watch you more closely for chemotherapy side effects, such as low blood counts, nerve symptoms, and fatigue.
What you should do: Keep taking both medicines exactly as prescribed unless your team tells you otherwise. Let your oncologist or pharmacist know you are on both, and report any new numbness, tingling, unusual bruising, fever, or extreme tiredness right away.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In a drug interaction study, giving belumosudil together with rosuvastatin (a substrate of OATP1B1 and BCRP) raised the rosuvastatin Cmax by 3.6-fold and the AUC by 4.6-fold, respectively 1.
Common questions
Can I take Paclitaxel and Belumosudil together?
Belumosudil can raise paclitaxel levels by blocking the OATP1B1 transporter, increasing the risk of chemotherapy toxicity, so your oncology team should avoid the combination when possible or adjust your dose and monitor you closely. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Paclitaxel 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 Paclitaxel and Belumosudil interaction managed?
What your care team may do: Try to avoid using these two together when another option exists. If both are needed, your paclitaxel dose may need to be adjusted and individualized by your oncology team. Watch you more closely for chemotherapy side effects, such as low blood counts, nerve symptoms, and fatigue. What you should do: Keep taking both medicines exactly as prescribed unless your team tell… 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 Paclitaxel 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 (1)
- Product Information: REZUROCK(R) oral tablets, belumosudil oral tablets. Kadmon Pharmaceuticals LLC (per FDA), Bridgewater, NJ, 2024. DailyMed
Keep reading about Belumosudil
Keep reading about Paclitaxel
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