Colchicine and Pacritinib: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 2, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Colchicine
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.
Colchicine (used for gout and pericarditis) is a drug your body clears partly through a pump in your gut and liver called P-glycoprotein (P-gp). Pacritinib (Vonjo) slows that pump down. When the pump is slowed, more colchicine can build up in your body, which can raise your chance of side effects like nausea, diarrhea, belly pain, or muscle problems.
Colchicine has a narrow safety window, so even small increases matter. The good news is this is very manageable. Do not stop or change either medicine on your own. Let your pharmacist or doctor know you take both so they can watch you more closely and adjust your colchicine dose if needed.
Interaction: Pacritinib inhibits P-gp-mediated efflux. Colchicine is a P-gp substrate with a narrow therapeutic index, so coadministration may increase colchicine exposure (AUC/Cmax) and the risk of dose-related toxicity (GI effects, myelosuppression, neuromyopathy, and at high exposures multiorgan toxicity).
- Direction: increased colchicine effect/toxicity via P-gp inhibition.
- Severity/Evidence: major; probable.
- Onset: unspecified.
- Management: monitor closely for colchicine adverse reactions; consider colchicine dose reduction individualized by the care team, particularly in renal or hepatic impairment. Neither agent requires prodrug consideration here.
What happens
Altered (reduced/increased) CYP3A4/P-gp substrate with NTI exposure, an increased risk of CYP3A4/P-gp substrate with NTI-related adverse reactions and reduced efficacy of CYP3A4/P-gp substrate with NTI
Interaction Deep Dive
When pacritinib, which acts as a CYP3A4 inducer, is given together with CYP3A4 substrates that have a narrow therapeutic index (NTI), the exposure to those substrates may be lowered, potentially diminishing their efficacy. In parallel, because pacritinib is a P-gp inhibitor, its concurrent use with P-gp substrates that have an NTI may raise the exposure to those P-gp substrates, thereby heightening the likelihood of adverse reactions attributable to the P-gp substrate. Should these agents be used together, the efficacy of the CYP3A4 substrate should be monitored more often, and monitoring for adverse reactions linked to the P-gp substrate should likewise be increased. A dose adjustment of the CYP3A4 substrates with NTI may be required1.
Why it happens (mechanism)
Inhibition of P-gp-mediated efflux transport by pacritinib; induction of CYP3A4-substrate metabolism by pacritinib
How to manage this interaction
This interaction can be managed safely with your care team's help.
- Keep taking both exactly as prescribed unless your prescriber tells you otherwise.
- Your team may monitor you more closely for colchicine side effects such as nausea, vomiting, diarrhea, muscle pain or weakness, or unusual tiredness.
- Your colchicine dose may need to be adjusted and individualized by your care team, especially if you have kidney or liver problems.
- Tell your pharmacist and prescriber you take both drugs, and report any new or worsening symptoms promptly.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) In a drug interaction study, giving pacritinib together with midazolam (a CYP3A4 substrate) may lower the Cmax and AUC of midazolam by 0.40-fold and 0.40-fold, respectively 1.
b) In a drug interaction study, administering pacritinib at a dose of 200 mg twice daily with digoxin (a P-gp substrate) 0.25 mg led to increases in digoxin Cmax and AUC of 1.29-fold and 1.15-fold, respectively 1.
Common questions
Can I take Colchicine and Pacritinib together?
Pacritinib can raise colchicine levels by blocking the P-gp pump, increasing the risk of colchicine side effects; keep taking both as prescribed and let your care team monitor you and adjust the colchicine dose if needed. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Colchicine 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 Colchicine and Pacritinib interaction managed?
This interaction can be managed safely with your care team's help. Keep taking both exactly as prescribed unless your prescriber tells you otherwise. Your team may monitor you more closely for colchicine side effects such as nausea, vomiting, diarrhea, muscle pain or weakness, or unusual tiredness. Your colchicine dose may need to be adjusted and individualized by your care team, especially if you… 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 Colchicine 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 Colchicine
Keep reading about Pacritinib
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major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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