Drug interactions
Estradiol + Phenytoin
Severity: Moderate
Estradiol and Phenytoin: 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
Phenytoin can reduce estradiol concentrations, causing diminished estrogen effect such as recurrence of vasomotor symptoms or breakthrough bleeding.
What this interaction means in plain words
Estradiol and Phenytoin 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.
Estradiol belongs to Endocrine; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4 and P-glycoprotein, increasing estradiol clearance.
What to do
Monitor for reduced estrogen effect and adjust the dose or consider a non-oral route or non-inducing antiseizure drug. Do not rely on estrogen-based contraception with phenytoin.
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?
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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
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 Phenytoin?
MediHelp rates the interaction as moderate. Estradiol and Phenytoin 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. Phenytoin can reduce estradiol concentrations, causing diminished estrogen effect such as recurrence of vasomotor symptoms or breakthrough bleeding.
How serious is the interaction between Estradiol and Phenytoin?
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 for reduced estrogen effect and adjust the dose or consider a non-oral route or non-inducing antiseizure drug. Do not rely on estrogen-based contraception with 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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