Drug interactions
Mifepristone + Tamoxifen
Severity: Moderate
Mifepristone and Tamoxifen: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Tamoxifen is converted by CYP3A4 to N-desmethyltamoxifen, which is then converted to endoxifen by CYP2D6. Mifepristone inhibits CYP3A4 and may alter the balance of metabolites, with uncertain effect on overall activity. Mifepristone also has antiprogestogenic effects on the endometrium.
What this interaction means in plain words
Mifepristone and Tamoxifen can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Mifepristone belongs to Endocrine; Tamoxifen belongs to Endocrine.
Why it happens
Mifepristone inhibits CYP3A4, altering tamoxifen metabolite formation; clinical consequence is not well established.
What to do
Monitor clinical response to tamoxifen and endometrial symptoms such as abnormal bleeding. Review the need for the combination if efficacy is a concern.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Mifepristone and Tamoxifen, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
Other interactions of Mifepristone
- Apixaban + Mifepristone Contraindicated
- Argatroban + Mifepristone Contraindicated
- Cisapride + Mifepristone Contraindicated
- Cortisone + Mifepristone Contraindicated
- Cyclosporin + Mifepristone Contraindicated
- Dabigatran etexilate + Mifepristone Contraindicated
Other interactions of Tamoxifen
- Amiodarone + Tamoxifen Major
- Anastrozole + Tamoxifen Major
- Bupropion + Tamoxifen Major
- Carbamazepine + Tamoxifen Major
- Cinacalcet + Tamoxifen Major
- Dacomitinib + Tamoxifen Major
Frequently asked questions
Can I take Mifepristone with Tamoxifen?
MediHelp rates the interaction as moderate. Mifepristone and Tamoxifen can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Tamoxifen is converted by CYP3A4 to N-desmethyltamoxifen, which is then converted to endoxifen by CYP2D6. Mifepristone inhibits CYP3A4 and may alter the balance of metabolites, with uncertain effect on overall activity. Mifepristone also has antiprogestogenic effects on the endometrium.
How serious is the interaction between Mifepristone and Tamoxifen?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor clinical response to tamoxifen and endometrial symptoms such as abnormal bleeding. Review the need for the combination if efficacy is a concern.
What other medicines interact with Mifepristone?
MediHelp also lists interactions of Mifepristone with, for example, Apixaban, Argatroban, Cisapride. The full list is on the Mifepristone page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
