Selumetinib and Encorafenib: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Encorafenib
Selumetinib
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.
What happens
Reduced selumetinib exposure and reduced efficacy of selumetinib
Interaction Deep Dive
Selumetinib and its active N-desmethyl metabolite are primarily metabolized by CYP3A4. In a pharmacokinetic trial, the concomitant use of rifAMPin (strong CYP3A4 inducer) decreased selumetinib AUC by 51% and Cmax by 26%. Coadministration with efavirenz (moderate CYP3A4 inducer) is predicted through modeling to reduce selumetinib AUC by 38% and Cmax by 22%. Avoid concomitant use of selumetinib with a strong or moderate CYP3A4 inducer as it may reduce selumetinib exposure, which may reduce efficacy of selumetinib1.
Why it happens (mechanism)
Induction of CYP3A4-mediated metabolism of selumetinib
Literature reports
1 report — tap to read
a) In a pharmacokinetic trial, the concomitant use of rifampicin (strong CYP3A4 inducer) decreased selumetinib AUC by 51% and Cmax by 26% in a clinical study. Coadministration with efavirenz (moderate CYP3A4 inducer) is predicted to reduce selumetinib AUC by 38% and Cmax by 22% 1.
Common questions
Can I take Selumetinib and Encorafenib together?
Reduced selumetinib exposure and reduced efficacy of selumetinib Always confirm with your pharmacist or prescriber before making any change.
How serious is the Selumetinib and Encorafenib 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 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 Selumetinib or Encorafenib 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: KOSELUGO® oral capsules, oral granules, selumetinib oral capsules, oral granules. AstraZeneca Pharmaceuticals LP (per Manufacturer), Wilmington, DE, 2025. DailyMed
Keep reading about Encorafenib
Keep reading about Selumetinib
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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