Drug interactions
Norethindrone transdermal + Phenytoin
Severity: Major
Norethindrone transdermal 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 may reduce norethindrone exposure from transdermal contraceptives, risking contraceptive failure and bleeding irregularities.
What this interaction means in plain words
Norethindrone transdermal 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 hormone clearance.
What to do
Prefer a copper IUD, levonorgestrel IUD or DMPA. If the patch is used, add a barrier method during and for about 28 days after 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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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 transdermal with Phenytoin?
MediHelp rates the interaction as major. Norethindrone transdermal 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 may reduce norethindrone exposure from transdermal contraceptives, risking contraceptive failure and bleeding irregularities.
How serious is the interaction between Norethindrone transdermal 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: Prefer a copper IUD, levonorgestrel IUD or DMPA. If the patch is used, add a barrier method during and for about 28 days after 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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