Drug interactions
Dienogest / estradiol valerate + Phenytoin
Severity: Major
Dienogest / estradiol valerate and Phenytoin: major interaction.
Last updated Sources: US FDA label
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
Phenytoin can lower estradiol and dienogest exposure, reducing contraceptive efficacy and increasing risk of breakthrough bleeding and unintended pregnancy. The effect persists after stopping phenytoin.
What this interaction means in plain words
Dienogest / estradiol valerate and Phenytoin 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
Phenytoin induces CYP3A4 metabolism of dienogest and estradiol.
What to do
Use a non-hormonal or other reliable contraceptive method such as a copper IUD instead. Continue alternative contraception for about 28 days after stopping phenytoin.
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?
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References
Other interactions of Phenytoin
- Artemether / lumefantrine + Phenytoin Contraindicated
- Bictegravir + Phenytoin Contraindicated
- Cabotegravir + Phenytoin Contraindicated
- Doravirine + Phenytoin Contraindicated
- Elbasvir / grazoprevir + Phenytoin Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Phenytoin Contraindicated
Frequently asked questions
Can I take Dienogest / estradiol valerate with Phenytoin?
MediHelp rates the interaction as major. Dienogest / estradiol valerate and Phenytoin 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. Phenytoin can lower estradiol and dienogest exposure, reducing contraceptive efficacy and increasing risk of breakthrough bleeding and unintended pregnancy. The effect persists after stopping phenytoin.
How serious is the interaction between Dienogest / estradiol valerate and Phenytoin?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Use a non-hormonal or other reliable contraceptive method such as a copper IUD instead. Continue alternative contraception for about 28 days after stopping phenytoin.
What other medicines interact with Phenytoin?
MediHelp also lists interactions of Phenytoin with, for example, Artemether / lumefantrine, Bictegravir, Cabotegravir. The full list is on the Phenytoin page.
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