Abemaciclib and Tocilizumab: 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
Abemaciclib
Tocilizumab
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 broken down in your body by a liver enzyme called CYP3A4. Tocilizumab (Actemra and similar brands) can speed that enzyme up. When the enzyme works faster, your body may clear abemaciclib more quickly, which can lower its level and possibly make your cancer treatment work less well.
This effect can last for several weeks even after tocilizumab is stopped. The good news is your care team can stay ahead of it. Please don't change or stop either medicine on your own. Just let your oncologist and pharmacist know you take both so they can watch how you're doing and adjust your dose if needed.
Mechanism: Tocilizumab, by normalizing IL-6-mediated suppression of CYP450, effectively induces CYP3A4. Abemaciclib is a CYP3A4 substrate, so co-administration may lower abemaciclib exposure (AUC/Cmax) and reduce antitumor efficacy.
- Direction: reduced CYP3A4 substrate exposure and efficacy.
- Evidence: probable; index substrates (omeprazole, simvastatin, dextromethorphan) showed decreased exposure ~1 week after a single tocilizumab dose.
- Onset/duration: effect may persist several weeks after tocilizumab discontinuation.
- Management: monitor therapeutic response; individualize/adjust abemaciclib dose on tocilizumab initiation or discontinuation.
What happens
Reduced CYP3A4 substrate with NTI exposure and reduced efficacy of CYP3A4 substrate with NTI
Interaction Deep Dive
Taking tocilizumab together with a CYP3A4 substrate that has a narrow therapeutic index (NTI) can lower the exposure of that substrate. Clinical trials demonstrated that CYP3A4 substrates (omeprazole, simvastatin, and dextromethorphan) had reduced exposure one week after a single tocilizumab dose. For patients receiving a CYP3A4 NTI substrate, monitor the therapeutic response or drug levels and modify the individual dose of that substrate as required when tocilizumab is started or stopped. Tocilizumab's influence on CYP450 enzyme activity can continue for several weeks following cessation of treatment. Exercise caution when tocilizumab is given alongside CYP3A4 substrate medications such as oral contraceptives, lovastatin, atorvastatin, and others, where a loss of effectiveness would be undesirable123.
Why it happens (mechanism)
Induction of CYP3A4-mediated metabolism by tocilizumab
How to manage this interaction
Keep taking both as prescribed unless your care team tells you otherwise. Because tocilizumab can lower abemaciclib levels, here is how a team usually handles this:
- They may monitor your response to abemaciclib more closely, especially when tocilizumab is started or stopped.
- Your abemaciclib dose may be adjusted and individualized by your oncologist as needed.
- Remember the effect can last several weeks after stopping tocilizumab, so monitoring may continue during that window.
What to do: Make sure your pharmacist and oncologist both know you take these two together, and report any new symptoms or concerns.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) In clinical trials, omeprazole, which is metabolized by CYP2C19 and CYP3A4, and simvastatin, which is metabolized by CYP3A4, demonstrated reductions in exposure of up to 28% and 57%, respectively, one week after a single dose of tocilizumab 13.
b) In drug interaction investigations, among 13 RA patients given 30 mg dextromethorphan (a substrate of CYP2D6 and CYP3A4), dextromethorphan exposure was similar to that seen in healthy subjects. Nevertheless, exposure to its metabolite dextrorphan (a CYP3A4 substrate) represented only a portion of what was observed in healthy subjects. One week after a single infusion of tocilizumab (8 mg per kg), dextromethorphan exposure fell by roughly 5%. However, a greater reduction (29%) in dextrorphan levels was observed following the tocilizumab infusion 2.
Common questions
Can I take Abemaciclib and Tocilizumab together?
Tocilizumab can speed up how your body clears abemaciclib, which may lower its levels and reduce cancer-treatment effectiveness; keep taking both as prescribed and let your oncologist and pharmacist monitor and adjust your dose as needed. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abemaciclib and Tocilizumab 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 Tocilizumab interaction managed?
Keep taking both as prescribed unless your care team tells you otherwise. Because tocilizumab can lower abemaciclib levels, here is how a team usually handles this: They may monitor your response to abemaciclib more closely, especially when tocilizumab is started or stopped. Your abemaciclib dose may be adjusted and individualized by your oncologist as needed. Remember the effect can last several… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Abemaciclib or Tocilizumab 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 (3)
- Product Information: AVTOZMA(R) intravenous, subcutanous injection, tocilizumab-anoh intravenous, subcutanous injection. CELLTRION USA, Inc. Jersey City, NJ, 2025. DailyMed
- Product Information: TYENNE(R) intravenous, subcutaneous injection, tocilizumab-aazg intravenous, subcutaneous injection. Fresenius Kabi USA, LLC (Per FDA), Lake Zurich, IL, 2024. DailyMed
- Product Information: TOFIDENCE(TM) intravenous injection, tocilizumab-bavi intravenous injection. Biogen MA Inc (per FDA), Cambridge, MA, 2023. DailyMed
Keep reading about Abemaciclib
Keep reading about Tocilizumab
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