Ciprofloxacin and Abemaciclib: 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
Ciprofloxacin
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.
Let's talk about taking ciprofloxacin (an antibiotic) along with abemaciclib (Verzenio, a cancer medicine). Your body uses a liver enzyme to break down abemaciclib. Ciprofloxacin can slow that enzyme down a bit, so more abemaciclib can build up in your blood.
When levels rise, you may be more likely to notice side effects like diarrhea, nausea, tiredness, or a drop in your blood counts. The good news is this is very manageable. Your care team may watch you more closely and, if needed, adjust your abemaciclib dose. Please don't stop or change either medicine on your own. Just let your pharmacist or oncologist know you're taking both.
Effect: Ciprofloxacin (moderate CYP3A4 inhibitor) may reduce CYP3A4-mediated metabolism of abemaciclib (a CYP3A4 substrate), increasing exposure of abemaciclib and its active metabolites, with potential for increased toxicity.
- Direction: Increased abemaciclib effect/toxicity (enzyme inhibition; neither agent is metabolized to gain activity in a way that reverses this).
- Evidence: Theoretical; onset unspecified.
- Monitor: Diarrhea, hepatotoxicity, neutropenia/CBC, ILD/pneumonitis, fatigue.
- Management: Consider dose reduction in 50 mg increments (150 mg BID to 100 mg to 50 mg; 200 mg BID to 150 mg to 100 mg to 50 mg); discontinue if 50 mg BID not tolerated.
What happens
Increased abemaciclib plasma concentration
Interaction Deep Dive
Taking abemaciclib (which is metabolized by CYP3A4) together with a moderate CYP3A4 inhibitor can raise the plasma concentrations of both abemaciclib and its active metabolite, potentially producing greater toxicity. When these agents are given together, watch for adverse reactions and consider decreasing the abemaciclib dose in 50-mg steps. Patients on 150 mg twice daily should first be lowered to 100 mg twice daily, then to 50 mg twice daily, with discontinuation if 50 mg twice daily cannot be tolerated. For those on 200 mg twice daily, reduce first to 150 mg twice daily, then to 100 mg twice daily, then to 50 mg twice daily, and discontinue if 50 mg twice daily is not tolerated1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated abemaciclib metabolism
How to manage this interaction
If you're prescribed both, your team can manage this safely. Typically they will:
- Watch you more closely for side effects such as diarrhea, nausea, fatigue, and changes in your blood counts or liver labs.
- Adjust your abemaciclib dose if needed, usually in 50 mg steps, tailored to how you tolerate it.
- Consider whether a different antibiotic is an option, if appropriate.
What you should do: Keep taking both exactly as prescribed unless told otherwise, and report any new or worsening side effects. Always let your pharmacist or oncologist know you're on both so they can plan monitoring and dosing.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) Within drug interaction studies, taking abemaciclib together with verapamil and diltiazem (moderate CYP3A inhibitors) is projected to raise the AUC of abemaciclib along with its active metabolites (M2, M18, and M20) by roughly 1.6-fold and 2.4-fold, respectively 1.
Common questions
Can I take Ciprofloxacin and Abemaciclib together?
Ciprofloxacin can raise abemaciclib levels and side effects; your care team can manage this by monitoring you and adjusting the abemaciclib dose if needed, so keep taking both as prescribed and tell your pharmacist or oncologist. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Ciprofloxacin and Abemaciclib 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 Ciprofloxacin and Abemaciclib interaction managed?
If you're prescribed both, your team can manage this safely. Typically they will: Watch you more closely for side effects such as diarrhea, nausea, fatigue, and changes in your blood counts or liver labs. Adjust your abemaciclib dose if needed, usually in 50 mg steps, tailored to how you tolerate it. Consider whether a different antibiotic is an option, if appropriate. What you should do: Keep tak… 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.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Ciprofloxacin or Abemaciclib 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, 2018. DailyMed
Keep reading about Ciprofloxacin
Keep reading about Abemaciclib
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