Drug interactions
Norethisterone + Primidone
Severity: Major
Norethisterone and Primidone: 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
Primidone is metabolized to phenobarbital and acts as an enzyme inducer, lowering norethisterone concentrations. Contraceptive reliability is reduced and breakthrough bleeding may occur.
What this interaction means in plain words
Norethisterone and Primidone 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.
Norethisterone belongs to Endocrine; Primidone belongs to Central Nervous System.
Why it happens
Primidone and its phenobarbital metabolite induce CYP3A4 and other hepatic enzymes, increasing norethisterone metabolism.
What to do
Use a copper IUD, levonorgestrel IUS or add barrier methods rather than relying on norethisterone alone. Continue extra precautions for several weeks after stopping primidone.
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 Norethisterone
- Acitretin + Norethisterone Contraindicated
- Amobarbital + Norethisterone Major
- Apalutamide + Norethisterone Major
- Belzutifan + Norethisterone Major
- Bosentan + Norethisterone Major
- Brigatinib + Norethisterone Major
Other interactions of Primidone
- Lorlatinib + Primidone Contraindicated
- Lurasidone + Primidone Contraindicated
- Primidone + Ranolazine Contraindicated
- Primidone + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
- Primidone + Voriconazole Contraindicated
- Abiraterone + Primidone Major
Frequently asked questions
Can I take Norethisterone with Primidone?
MediHelp rates the interaction as major. Norethisterone and Primidone 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. Primidone is metabolized to phenobarbital and acts as an enzyme inducer, lowering norethisterone concentrations. Contraceptive reliability is reduced and breakthrough bleeding may occur.
How serious is the interaction between Norethisterone and Primidone?
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 copper IUD, levonorgestrel IUS or add barrier methods rather than relying on norethisterone alone. Continue extra precautions for several weeks after stopping primidone.
What other medicines interact with Norethisterone?
MediHelp also lists interactions of Norethisterone with, for example, Acitretin, Amobarbital, Apalutamide. The full list is on the Norethisterone page.
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