Abemaciclib and Conivaptan: 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
Conivaptan
Abemaciclib
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 conivaptan and abemaciclib (Verzenio) together. Abemaciclib is a cancer medicine your liver breaks down using an enzyme called CYP3A4. Conivaptan slows that enzyme down, so your body may clear the abemaciclib more slowly. That can let abemaciclib build up to higher levels than usual.
Higher levels can mean stronger side effects, like diarrhea, tiredness, or a drop in your blood counts. The good news is this is very manageable. Your care team can lower your abemaciclib dose while you're on conivaptan and watch you a little more closely. Please don't change anything on your own, just check in with your oncologist or pharmacist.
Effect: Increased abemaciclib exposure (parent drug and active metabolites) via conivaptan inhibition of CYP3A4-mediated metabolism. Abemaciclib is an active drug (not a prodrug), so reduced clearance raises plasma levels and toxicity risk.
- Direction: Increased abemaciclib effect/toxicity.
- Evidence: Theoretical; onset unspecified.
- Monitoring: Watch for diarrhea, neutropenia, hepatotoxicity, fatigue.
- Management (per labeling): If starting dose was 200 mg or 150 mg BID, reduce to 100 mg BID. If already reduced to 100 mg BID for adverse reactions, reduce further to 50 mg BID. After stopping the inhibitor, resume the prior dose following 3 to 5 inhibitor half-lives.
What happens
Increased abemaciclib plasma concentration
Interaction Deep Dive
Taking abemaciclib together with a potent CYP3A4 inhibitor can raise the plasma concentrations of both abemaciclib and its active metabolite, potentially increasing toxicity. When these agents are given together and abemaciclib was begun at either 200 mg or 150 mg twice daily, the abemaciclib dose should be lowered to 100 mg twice daily. For patients whose dose has already been decreased to 100 mg twice daily because of adverse reactions, abemaciclib should be further cut to 50 mg twice daily. Once the strong CYP3A inhibitor is stopped, the abemaciclib dose should be raised again (after 3-5 half-lives of the inhibitor have elapsed) back to the level given prior to starting the strong inhibitor1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated abemaciclib metabolism
How to manage this interaction
The main tool here is adjusting the abemaciclib dose and watching you more closely while you're on conivaptan.
- Keep taking both medicines exactly as prescribed unless your care team tells you otherwise.
- Your oncology team may lower the abemaciclib dose during conivaptan use, and then raise it back to your previous dose after the conivaptan has cleared from your system.
- Tell your team promptly about side effects like diarrhea, fever or signs of infection, unusual tiredness, or yellowing of the skin or eyes.
Confirm the specific dosing plan with your prescriber or pharmacist so it's tailored to you.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) Drug interaction studies predict that giving abemaciclib together with itraconazole (a strong CYP3A inhibitor) will raise the AUC of abemaciclib along with its active metabolites (M2, M18 and M20) by 2.2-fold 1.
b) In drug interaction studies conducted in cancer patients, administering a single 50 mg dose of abemaciclib (0.3 times the approved 150 mg dose) alongside clarithromycin 500 mg twice daily (a strong CYP3A inhibitor) raised the AUC(0 to infinity) of abemaciclib together with its active metabolites (M2, M18, and M20) by 1.7-fold relative to abemaciclib given alone 1.
Common questions
Can I take Abemaciclib and Conivaptan together?
Conivaptan can raise abemaciclib levels and side effects by slowing its breakdown, so your care team may lower the abemaciclib dose and monitor you more closely while you take both. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abemaciclib and Conivaptan interaction?
It is rated moderate. Can be significant — usually manageable with 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 Conivaptan interaction managed?
The main tool here is adjusting the abemaciclib dose and watching you more closely while you're on conivaptan. Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. Your oncology team may lower the abemaciclib dose during conivaptan use, and then raise it back to your previous dose after the conivaptan has cleared from your system. Tell your team promptly abou… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Abemaciclib or Conivaptan 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 anything you'd monitor while I'm on both?
References (1)
- Product Information: VERZENIO(TM) oral tablets, abemaciclib oral tablets. Lilly USA LLC (per FDA), Indianapolis, IN, 2017. DailyMed
Keep reading about Conivaptan
Keep reading about Abemaciclib
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