Abemaciclib and Dabrafenib: 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
Dabrafenib
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. Dabrafenib (Tafinlar) speeds up an enzyme in your liver called CYP3A4. That same enzyme breaks down abemaciclib (Verzenio). So when you take them together, your body may clear abemaciclib faster than it should, leaving less of it in your blood.
The concern isn't more side effects here, it's that abemaciclib, which is a cancer medicine, may not work as well. That's why this matters. The good news is your cancer care team can manage this. Please don't change anything on your own. Just talk with your oncologist or pharmacist so they can pick the safest plan for you.
Mechanism: Dabrafenib is a moderate CYP3A4 inducer; abemaciclib is a sensitive CYP3A4 substrate. Concurrent use increases abemaciclib metabolism, lowering its plasma exposure (AUC/Cmax) and risking reduced antineoplastic efficacy.
- Direction: Reduced abemaciclib exposure and effect.
- Magnitude: Dabrafenib reduced midazolam AUC by ~65%; a comparable effect is plausible for abemaciclib.
- Onset: Unspecified; enzyme induction typically develops over days.
- Evidence: Probable.
- Management: Avoid the combination and substitute where possible; if unavoidable, monitor closely for loss of abemaciclib efficacy. Neither drug is a prodrug requiring activation.
What happens
Reduced sensitive CYP3A4 substrate exposure
Interaction Deep Dive
Giving dabrafenib, which induces CYP3A4, together with sensitive CYP3A4 substrates can lower the plasma levels of those substrates, potentially causing them to lose effectiveness. In drug interaction studies, dabrafenib reduced the AUC of midazolam (a CYP3A4 substrate) by 65%. Since other CYP3A4 substrates are likely to behave similarly, these drugs should be replaced with alternatives, or, when that cannot be avoided, patients should be watched for any loss of efficacy of these medications1.
Why it happens (mechanism)
Induction of CYP3A4 substrate metabolism by dabrafenib
How to manage this interaction
What your care team may do:
- Consider substituting one of the drugs for an alternative that does not affect CYP3A4, when a suitable option exists.
- If both must be used together, monitor you more closely for signs that abemaciclib may not be working as well.
- Doses may be adjusted and individualized by your oncology team.
What you should do: Keep taking both exactly as prescribed unless your prescriber tells you otherwise. Ask your pharmacist or oncologist whether this combination is right for you and mention any new or returning symptoms.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In drug interaction studies, giving dabrafenib 150 mg twice daily for 15 days together with a single dose of midazolam (a CYP3A4 substrate) reduced the AUC of midazolam by 65% 1.
Common questions
Can I take Abemaciclib and Dabrafenib together?
Dabrafenib can lower abemaciclib levels and make it work less well; your oncology team may switch one drug or watch you more closely, so keep taking both as prescribed and check with them. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abemaciclib and Dabrafenib 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 Dabrafenib interaction managed?
What your care team may do: Consider substituting one of the drugs for an alternative that does not affect CYP3A4, when a suitable option exists. If both must be used together, monitor you more closely for signs that abemaciclib may not be working as well. Doses may be adjusted and individualized by your oncology team. What you should do: Keep taking both exactly as prescribed unless your prescrib… 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 Dabrafenib 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: TAFINLAR(R) oral capsules, tablets for suspension, dabrafenib oral capsules, tablets for suspension. Novartis Pharmaceuticals Corporation (per FDA), East Hanover, NJ, 2023. DailyMed
Keep reading about Dabrafenib
Keep reading about Abemaciclib
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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