Drug interactions
Estradiol + Phenindione
Severity: Major
Estradiol and Phenindione: major 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
Estrogens increase coagulation factor levels and can reduce the effect of oral anticoagulants such as phenindione, leading to inadequate anticoagulation and thrombotic risk.
What this interaction means in plain words
Estradiol and Phenindione can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Estradiol increases hepatic synthesis of vitamin K-dependent clotting factors, opposing vitamin K antagonist effect.
What to do
Avoid estrogen in patients needing anticoagulation where possible. If used, monitor INR frequently and adjust the phenindione dose.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Estradiol and Phenindione, 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 Estradiol
- Anastrozole + Estradiol Contraindicated
- Estradiol + Fezolinetant Contraindicated
- Estradiol + Ospemifene Contraindicated
- Antithrombin alfa + Estradiol Major
- Antithrombin iii + Estradiol Major
- Estradiol + Exemestane Major
Frequently asked questions
Can I take Estradiol with Phenindione?
MediHelp rates the interaction as major. Estradiol and Phenindione can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Estrogens increase coagulation factor levels and can reduce the effect of oral anticoagulants such as phenindione, leading to inadequate anticoagulation and thrombotic risk.
How serious is the interaction between Estradiol and Phenindione?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid estrogen in patients needing anticoagulation where possible. If used, monitor INR frequently and adjust the phenindione dose.
What other medicines interact with Estradiol?
MediHelp also lists interactions of Estradiol with, for example, Anastrozole, Fezolinetant, Ospemifene. The full list is on the Estradiol 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.
