Drug interactions
Ethinyl estradiol-levonorgestrel + Phenindione
Severity: Major
Ethinyl estradiol-levonorgestrel and Phenindione: major interaction.
Last updated Sources: UK SmPC
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
Estrogen-containing contraceptives increase clotting factor levels and thrombotic risk, which can oppose the anticoagulant effect of phenindione. This may reduce anticoagulation and INR control in a patient who already needs anticoagulation for thrombosis.
What this interaction means in plain words
Ethinyl estradiol-levonorgestrel 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
Pharmacodynamic antagonism: estrogen raises procoagulant factor levels, counteracting vitamin K antagonism.
What to do
Avoid estrogen-containing contraceptives in patients needing anticoagulation and use a progestogen-only or non-hormonal method. Monitor INR closely if the combination cannot be avoided.
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 Ethinyl estradiol-levonorgestrel 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.
References
Other interactions of Ethinyl estradiol-levonorgestrel
- Ethinyl estradiol-levonorgestrel + Fezolinetant Contraindicated
- Ethinyl estradiol-levonorgestrel + Ombitasvir / paritaprevir / ritonavir and dasabuvir Contraindicated
- Ethinyl estradiol-levonorgestrel + Tranexamic acid Contraindicated
- Aminocaproic acid + Ethinyl estradiol-levonorgestrel Major
- Amobarbital + Ethinyl estradiol-levonorgestrel Major
- Anastrozole + Ethinyl estradiol-levonorgestrel Major
Frequently asked questions
Can I take Ethinyl estradiol-levonorgestrel with Phenindione?
MediHelp rates the interaction as major. Ethinyl estradiol-levonorgestrel 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. Estrogen-containing contraceptives increase clotting factor levels and thrombotic risk, which can oppose the anticoagulant effect of phenindione. This may reduce anticoagulation and INR control in a patient who already needs anticoagulation for thrombosis.
How serious is the interaction between Ethinyl estradiol-levonorgestrel 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-containing contraceptives in patients needing anticoagulation and use a progestogen-only or non-hormonal method. Monitor INR closely if the combination cannot be avoided.
What other medicines interact with Ethinyl estradiol-levonorgestrel?
MediHelp also lists interactions of Ethinyl estradiol-levonorgestrel with, for example, Fezolinetant, Ombitasvir / paritaprevir / ritonavir and dasabuvir, Tranexamic acid. The full list is on the Ethinyl estradiol-levonorgestrel 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.
