Abemaciclib and Telaprevir: 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
Telaprevir
No brand names on recordAbemaciclib
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. Abemaciclib (Verzenio) is a cancer medicine your body breaks down using a liver enzyme called CYP3A4. Telaprevir slows that enzyme down. When the enzyme is blocked, abemaciclib can build up in your blood to higher levels than intended.
Higher levels can mean more side effects, like diarrhea, nausea, tiredness, or changes in your blood counts. The good news is this is very manageable. Your care team can lower your abemaciclib dose while you're on telaprevir and watch you a little more closely. Please don't change anything on your own, just check in with your doctor or pharmacist.
Mechanism: Telaprevir is a strong CYP3A4 inhibitor. Abemaciclib is a CYP3A4 substrate (active drug, not a prodrug), so inhibition reduces its metabolism and increases plasma exposure of abemaciclib and its active metabolites.
Effect: Increased AUC/Cmax, higher risk of dose-related toxicity (diarrhea, neutropenia, hepatotoxicity, fatigue).
Evidence: Theoretical; onset unspecified. Severity moderate.
Management per labeling:
- Starting dose 200 or 150 mg BID: reduce to 100 mg BID.
- Already reduced to 100 mg BID for adverse reactions: reduce further to 50 mg BID.
- On inhibitor discontinuation, after 3-5 half-lives, resume prior dose.
- Monitor for abemaciclib toxicity.
What happens
Increased abemaciclib plasma concentration
Interaction Deep Dive
Taking abemaciclib together with a potent CYP3A4 inhibitor can raise plasma concentrations of both abemaciclib and its active metabolite, potentially heightening toxicity. When these agents are given together and the initial abemaciclib dose was either 200 mg or 150 mg twice daily, lower the abemaciclib dose to 100 mg twice daily. For patients whose dose has already been decreased to 100 mg twice daily because of adverse reactions, cut the abemaciclib dose further to 50 mg twice daily. Once the strong CYP3A inhibitor has been stopped, raise the abemaciclib dose back to the level used prior to starting the strong inhibitor, doing so after 3-5 half-lives of the inhibitor have elapsed1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated abemaciclib metabolism
How to manage this interaction
This interaction can be managed. Because telaprevir can raise abemaciclib levels, your care team will typically tailor your dose and keep a closer eye on you.
- Keep taking both exactly as prescribed unless your team tells you otherwise.
- Your oncology team may lower your abemaciclib dose while you are on telaprevir (for example, stepping down to a lower twice-daily dose), then raise it back up once telaprevir is stopped.
- Report side effects like diarrhea, fever, unusual tiredness, or signs of low blood counts.
Ask your pharmacist or oncologist before starting or stopping either medicine so they can adjust the plan.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) In drug interaction studies, giving abemaciclib together with itraconazole (a strong CYP3A inhibitor) is projected to 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 dosage) alongside clarithromycin 500 mg twice daily (a strong CYP3A inhibitor) raised the AUC(0 to infinity) of abemaciclib plus its active metabolites (M2, M18, and M20) by 1.7-fold relative to abemaciclib given alone 1.
Common questions
Can I take Abemaciclib and Telaprevir together?
Telaprevir can raise abemaciclib levels and increase side effects, so your oncology team will likely lower the abemaciclib dose and monitor you more closely while you take both. Don't change doses on your own, check with your care team. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abemaciclib and Telaprevir 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 Telaprevir interaction managed?
This interaction can be managed. Because telaprevir can raise abemaciclib levels, your care team will typically tailor your dose and keep a closer eye on you. Keep taking both exactly as prescribed unless your team tells you otherwise. Your oncology team may lower your abemaciclib dose while you are on telaprevir (for example, stepping down to a lower twice-daily dose), then raise it back up once… 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 Telaprevir 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 Telaprevir
Keep reading about Abemaciclib
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