Abemaciclib and Pacritinib: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 10, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Abemaciclib
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.
Let's talk about taking Verzenio (abemaciclib) together with Vonjo (pacritinib). Abemaciclib is your cancer medicine, and it's broken down by a liver enzyme called CYP3A4. Pacritinib can speed that enzyme up, which means your body may clear abemaciclib faster than it should. When that happens, the level of your cancer medicine can drop, and it may not work as well as it needs to.
The good news is that this is manageable. Your care team can watch how well your treatment is working and adjust your dose if needed. Please don't stop or change either medicine on your own. Just bring this up with your oncologist or pharmacist so they can keep an eye on things.
Effect: Pacritinib induces CYP3A4, potentially increasing abemaciclib metabolism and reducing its exposure (AUC/Cmax) and antitumor efficacy.
- Mechanism: CYP3A4 induction by pacritinib accelerating clearance of the substrate abemaciclib.
- Direction: Reduced abemaciclib effect (neither drug is a prodrug here).
- Severity/Evidence: Major; probable substantiation. Onset unspecified.
- Management: Monitor efficacy/clinical response more frequently. Abemaciclib dose may need to be adjusted and individualized. Consider alternative agents with less CYP3A4 induction if feasible.
What happens
Reduced CYP3A4 substrate with NTI exposure and reduced efficacy of CYP3A4 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 NTI CYP3A4 substrates may decline, potentially lowering their efficacy as well. During concurrent use of pacritinib and CYP3A4 substrates with NTI, the efficacy of the CYP3A4 substrate should be assessed more often. Adjusting the dose of the CYP3A4 substrates with NTI may become necessary1.
Why it happens (mechanism)
Induction of CYP3A4-substrate metabolism by pacritinib
How to manage this interaction
Here's how a care team usually handles this combination:
- Keep taking both exactly as prescribed unless your team tells you otherwise.
- Closer monitoring: Your oncologist may check how well your cancer treatment is working more often while you're on both drugs.
- Possible dose adjustment: Your abemaciclib dose may need to be adjusted and individualized by your care team.
- Alternatives: Ask whether a different medicine that doesn't speed up this liver enzyme might be an option.
Raise any concerns about your treatment working with your pharmacist or prescriber.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) During a drug interaction study, giving pacritinib at a dose of 200 mg twice daily together with midazolam (a CYP3A4 substrate) may lead to decreases in midazolam Cmax and AUC of 0.40-fold and 0.40-fold, respectively 1.
Common questions
Can I take Abemaciclib and Pacritinib together?
Pacritinib can lower abemaciclib levels and make your cancer medicine less effective, so your care team may monitor you more closely and adjust your dose. Keep taking both as prescribed and talk with your oncologist or pharmacist. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abemaciclib 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 Abemaciclib and Pacritinib interaction managed?
Here's how a care team usually handles this combination: Keep taking both exactly as prescribed unless your team tells you otherwise. Closer monitoring: Your oncologist may check how well your cancer treatment is working more often while you're on both drugs. Possible dose adjustment: Your abemaciclib dose may need to be adjusted and individualized by your care team. Alternatives: Ask whether a di… 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 Abemaciclib 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 Abemaciclib
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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