Abemaciclib and Enzalutamide: 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
Enzalutamide
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.
Here's what's going on. Enzalutamide (Xtandi) speeds up a liver enzyme called CYP3A4, which is the same enzyme that breaks down abemaciclib (Verzenio). When they're taken together, your body clears abemaciclib faster, so its blood levels drop. In one study using a strong version of this kind of drug, abemaciclib levels fell by about two-thirds.
The worry here is not extra side effects but that abemaciclib may not work as well against your cancer if its levels are too low. This is important, so please don't change anything on your own. Talk with your oncology team, who can look at your specific plan and choose the safest, most effective option for you.
Mechanism: Enzalutamide is a strong CYP3A4 inducer; abemaciclib is a CYP3A4 substrate (active parent plus active metabolites). Coadministration increases abemaciclib clearance, reducing plasma exposure of both the drug and its active metabolites.
- Direction: Reduced abemaciclib effect (potential loss of antitumor efficacy).
- Magnitude: Rifampin (strong inducer) decreased abemaciclib AUC by ~67%; enzalutamide effect extrapolated, evidence theoretical.
- Onset: Unspecified; enzymatic induction typically develops over 1 to 2 weeks.
- Management: Avoid coadministration. Select an alternative to enzalutamide or a non-inducing regimen. If unavoidable, dosing may need individualization and closer monitoring of response by the care team.
What happens
Decreased abemaciclib plasma concentration
Interaction Deep Dive
Taking abemaciclib together with a potent CYP3A4 inducer can lower the plasma concentrations of both abemaciclib and its active metabolite, potentially reducing therapeutic effectiveness. Clinical studies showed that giving rifampin (a strong CYP3A4 inducer) alongside abemaciclib reduced abemaciclib exposure by 67%. This combination should not be used, and alternative agents should be considered1.
Why it happens (mechanism)
Induction of CYP3A4-mediated abemaciclib metabolism
How to manage this interaction
What your care team may do: Because enzalutamide can lower abemaciclib levels enough to reduce how well it works, guidance is to avoid using them together when possible.
- Your oncology team may choose an alternative medication to one of these drugs to protect your cancer treatment.
- If both are truly needed, your dose may be adjusted and individualized, and your team may monitor your response more closely.
What you should do: Keep taking both exactly as prescribed for now, and do not stop or change either one on your own. Ask your pharmacist or oncologist whether this combination is right for you and whether an alternative makes sense.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In drug interaction investigations conducted in healthy volunteers, giving a single 200 mg dose of abemaciclib together with rifampin 600 mg daily (a potent CYP3A inducer) reduced the AUC(0 to infinity) of abemaciclib along with its active metabolites (M2, M18, and M20) by 67% 1.
Common questions
Can I take Abemaciclib and Enzalutamide together?
Enzalutamide can speed up how your body clears abemaciclib, lowering its levels and possibly making it less effective, so this combination is generally avoided. Ask your oncology team about an alternative before changing anything. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abemaciclib and Enzalutamide 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 Enzalutamide interaction managed?
What your care team may do: Because enzalutamide can lower abemaciclib levels enough to reduce how well it works, guidance is to avoid using them together when possible. Your oncology team may choose an alternative medication to one of these drugs to protect your cancer treatment. If both are truly needed, your dose may be adjusted and individualized, and your team may monitor your response more c… 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 Enzalutamide 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: VERZENIO(TM) oral tablets, abemaciclib oral tablets. Lilly USA LLC (per FDA), Indianapolis, IN, 2017. DailyMed
Keep reading about Enzalutamide
Keep reading about Abemaciclib
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