Drug interactions
Phenytoin + Progesterone
Severity: Major
Phenytoin and Progesterone: 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
Phenytoin accelerates progesterone metabolism, decreasing its exposure and effect. This risks contraceptive failure, breakthrough bleeding, and inadequate endometrial protection.
What this interaction means in plain words
Phenytoin and Progesterone 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 belongs to Central Nervous System; Progesterone belongs to Endocrine.
Why it happens
Phenytoin induces CYP3A4 and other enzymes, increasing progesterone clearance.
What to do
Recommend non-hormonal contraception. When progesterone is needed therapeutically, monitor response and consider dose adjustment or an alternative.
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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Other interactions of Progesterone
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 Phenytoin with Progesterone?
MediHelp rates the interaction as major. Phenytoin and Progesterone 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 accelerates progesterone metabolism, decreasing its exposure and effect. This risks contraceptive failure, breakthrough bleeding, and inadequate endometrial protection.
How serious is the interaction between Phenytoin and Progesterone?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Recommend non-hormonal contraception. When progesterone is needed therapeutically, monitor response and consider dose adjustment or an alternative.
What other medicines interact with Progesterone?
MediHelp also lists interactions of Progesterone with, for example, Apalutamide, Carbamazepine, Enzalutamide. The full list is on the Progesterone page.
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