Abemaciclib and Telithromycin: 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
Telithromycin
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. Telithromycin is an antibiotic that slows down a liver enzyme (called CYP3A4) that your body uses to break down abemaciclib, your cancer medicine. When that breakdown slows, more abemaciclib builds up in your blood. That can mean more side effects, like diarrhea, low blood counts, tiredness, or nausea.
The good news is that this is very manageable. Your care team knows about this and can lower your abemaciclib dose while you're on the antibiotic, then put it back once the antibiotic is finished. Please don't change anything on your own. Just check in with your doctor or pharmacist so they can adjust and watch you closely.
Mechanism: Telithromycin is a strong CYP3A4 inhibitor. Abemaciclib is a CYP3A4 substrate (active drug, not a prodrug), so inhibition reduces its metabolism and raises plasma levels of abemaciclib and its active metabolites, increasing toxicity risk.
- Direction: Increased abemaciclib exposure (AUC/Cmax)
- Evidence: Theoretical; severity moderate
- Onset: Unspecified
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, further reduce to 50 mg BID. On stopping telithromycin, resume prior dose after 3 to 5 inhibitor half-lives. Monitor for toxicity (diarrhea, myelosuppression, hepatotoxicity, VTE).
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, reduce the abemaciclib dose further to 50 mg twice daily. Once the strong CYP3A inhibitor has been stopped, wait 3-5 half-lives of the inhibitor and then raise the abemaciclib dose back to the level that had been used prior to starting the strong inhibitor1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated abemaciclib metabolism
How to manage this interaction
Keep taking both medicines as prescribed unless your care team tells you otherwise. This combination is manageable with dose adjustment and monitoring.
- Your team may lower your abemaciclib dose while you are on telithromycin, following standard step-downs (for example from 150 or 200 mg twice daily to 100 mg twice daily, and further to 50 mg twice daily if you already needed a reduction for side effects).
- When the antibiotic is stopped, your dose can be raised back to what it was before, after the antibiotic clears.
- Watch for and report diarrhea, unusual tiredness, fever, or signs of low blood counts.
Ask your pharmacist or oncologist before starting or stopping either drug.
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 administered alone 1.
Common questions
Can I take Abemaciclib and Telithromycin together?
Telithromycin can raise abemaciclib levels and side-effect risk by blocking its breakdown; your oncology team can safely handle this by lowering the abemaciclib dose during treatment and restoring it afterward. Keep both as prescribed and check with your doctor or pharmacist. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abemaciclib and Telithromycin 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 Telithromycin interaction managed?
Keep taking both medicines as prescribed unless your care team tells you otherwise. This combination is manageable with dose adjustment and monitoring. Your team may lower your abemaciclib dose while you are on telithromycin, following standard step-downs (for example from 150 or 200 mg twice daily to 100 mg twice daily, and further to 50 mg twice daily if you already needed a reduction for side e… 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 Telithromycin 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 Telithromycin
Keep reading about Abemaciclib
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