Simvastatin and Pacritinib: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 4, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Simvastatin
Pacritinib
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. Pacritinib (Vonjo) can block a doorway in your body called BCRP that normally helps push certain drugs out. Simvastatin (Zocor) relies partly on that doorway, so when the two are taken together, more simvastatin can build up in your system than usual.
More simvastatin means a higher chance of statin side effects, especially muscle aches, soreness, or weakness, and rarely, muscle problems that affect the kidneys. The good news is this is very manageable. Your care team can adjust your simvastatin dose and keep a closer eye on you. Please don't stop either medicine on your own, just check in with your pharmacist or doctor about the combination.
Mechanism: Pacritinib inhibits BCRP-mediated efflux, reducing clearance of BCRP substrates and increasing their systemic exposure. Simvastatin (and its active acid) is a BCRP substrate, so coadministration is expected to raise simvastatin exposure and statin-related adverse-reaction risk (myalgia, myopathy, rarely rhabdomyolysis).
- Direction: increased simvastatin exposure (increases drug effect/toxicity).
- Magnitude: not quantified for simvastatin; reference substrate rosuvastatin showed AUC 1.80-fold, Cmax 2-fold.
- Evidence: probable. Onset: unspecified.
- Management: monitor for statin adverse effects more frequently; consider dose reduction of the BCRP substrate (simvastatin).
What happens
Increased BCRP substrate exposure and an increased risk of BCRP substrate-related adverse reactions
Interaction Deep Dive
Giving pacritinib (a BCRP inhibitor) together with BCRP substrates can raise the exposure of those substrates, potentially heightening the risk of adverse reactions attributable to the BCRP substrates. During concurrent use with pacritinib, watch more closely for adverse reactions linked to the BCRP substrate and weigh reducing the substrate's dose. A drug interaction study showed that administering pacritinib at 200 mg twice daily along with rosuvastatin 5 mg produced a 1.80-fold rise in rosuvastatin AUC and a 2-fold rise in Cmax1.
Why it happens (mechanism)
Inhibition of BCRP-mediated efflux transport by pacritinib
How to manage this interaction
This is manageable with a few sensible steps. Keep taking both medicines exactly as prescribed unless your care team tells you otherwise.
- Your team may reduce your simvastatin dose while you are on pacritinib, individualized to you.
- They will likely watch you more closely for statin side effects.
- Report new or worsening muscle pain, tenderness, or weakness, unusual tiredness, or dark-colored urine promptly.
Ask your pharmacist or prescriber whether your simvastatin dose should be adjusted now that you are taking pacritinib. Don't change or stop either drug on your own.
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 pacritinib at a dose of 200 mg twice daily together with rosuvastatin 5 mg produced a 1.80-fold rise in rosuvastatin AUC and a 2-fold rise in Cmax 1.
Common questions
Can I take Simvastatin and Pacritinib together?
Pacritinib can raise simvastatin levels and increase the risk of muscle-related statin side effects, so your care team may lower the simvastatin dose and monitor you more closely. Watch for muscle pain or weakness and report it. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Simvastatin and Pacritinib 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 Simvastatin and Pacritinib interaction managed?
This is manageable with a few sensible steps. Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. Your team may reduce your simvastatin dose while you are on pacritinib, individualized to you. They will likely watch you more closely for statin side effects. Report new or worsening muscle pain, tenderness, or weakness, unusual tiredness, or dark-colored urine… 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.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Simvastatin or Pacritinib 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: VONJO(R) oral capsules, pacritinib oral capsules. CTI BioPharma Corp (per FDA), Seattle, WA, 2024. DailyMed
Keep reading about Simvastatin
Keep reading about Pacritinib
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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