Elacestrant and Phenytoin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Phenytoin
Elacestrant
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 elacestrant exposure and reduced efficacy of elacestrant
Interaction Deep Dive
Avoid concomitant use of elacestrant with strong CYP3A4 inducers. Concomitant use of elacestrant with strong CYP3A4 inducers reduces elacestrant exposure which may reduce the effectiveness of elacestrant. Concomitant use of 345 mg single dose of elacestrant with rifampin decreased the AUC and Cmax of elacestrant by 86% and 73% respectively1.
Why it happens (mechanism)
Induction of CYP3A4-mediated metabolism of elacestrant
Literature reports
1 report — tap to read
a) Concomitant use of 345 mg single dose of elacestrant with rifampin (a strong CYP3A inducer) decreased the AUC and Cmax of elacestrant by 86% and 73% respectively 1.
Common questions
Can I take Elacestrant and Phenytoin together?
Reduced elacestrant exposure and reduced efficacy of elacestrant Always confirm with your pharmacist or prescriber before making any change.
How serious is the Elacestrant and Phenytoin 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 "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Elacestrant or Phenytoin 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: ORSERDU(TM) oral tablets, elacestrant oral tablets. Stemline Therapeutics (per FDA), New York, NY, 2023. DailyMed
Keep reading about Phenytoin
Keep reading about Elacestrant
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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