Drug interactions
Norethindrone + Phenytoin
Severity: Major
Norethindrone and Phenytoin: 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 lowers progestin levels and can cause contraceptive failure and breakthrough bleeding or other menstrual disturbances. Unplanned pregnancy on phenytoin carries fetal risk.
What this interaction means in plain words
Norethindrone 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 hepatic CYP3A4, increasing norethindrone clearance.
What to do
Use a non-affected method such as a copper IUD, levonorgestrel IUD or DMPA. If hormonal pills are used, add a barrier method and continue it for about 28 days after phenytoin is stopped.
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 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 Norethindrone with Phenytoin?
MediHelp rates the interaction as major. Norethindrone 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 lowers progestin levels and can cause contraceptive failure and breakthrough bleeding or other menstrual disturbances. Unplanned pregnancy on phenytoin carries fetal risk.
How serious is the interaction between Norethindrone 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-affected method such as a copper IUD, levonorgestrel IUD or DMPA. If hormonal pills are used, add a barrier method and continue it for about 28 days after phenytoin is stopped.
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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