Drug interactions
Ethinyl estradiol-levonorgestrel + Primidone
Severity: Major
Ethinyl estradiol-levonorgestrel and Primidone: major interaction.
Last updated Sources: UK SmPC
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 partly converted to phenobarbital and induces hepatic enzymes, which accelerates clearance of contraceptive hormones. Reduced hormone exposure can cause breakthrough bleeding and contraceptive failure.
What this interaction means in plain words
Ethinyl estradiol-levonorgestrel 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.
Ethinyl estradiol-levonorgestrel belongs to Endocrine; Primidone belongs to Central Nervous System.
Why it happens
Enzyme induction (CYP3A4) by primidone and its metabolite phenobarbital increases metabolism of ethinyl estradiol and levonorgestrel.
What to do
Advise a non-hormonal or non-enzyme-sensitive contraceptive method such as a copper IUD or a medroxyprogesterone injection. Continue it for several weeks after primidone 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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References
Other interactions of Ethinyl estradiol-levonorgestrel
- Ethinyl estradiol-levonorgestrel + Fezolinetant Contraindicated
- Ethinyl estradiol-levonorgestrel + Ombitasvir / paritaprevir / ritonavir and dasabuvir Contraindicated
- Ethinyl estradiol-levonorgestrel + Tranexamic acid Contraindicated
- Aminocaproic acid + Ethinyl estradiol-levonorgestrel Major
- Amobarbital + Ethinyl estradiol-levonorgestrel Major
- Anastrozole + Ethinyl estradiol-levonorgestrel 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 Ethinyl estradiol-levonorgestrel with Primidone?
MediHelp rates the interaction as major. Ethinyl estradiol-levonorgestrel 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 partly converted to phenobarbital and induces hepatic enzymes, which accelerates clearance of contraceptive hormones. Reduced hormone exposure can cause breakthrough bleeding and contraceptive failure.
How serious is the interaction between Ethinyl estradiol-levonorgestrel 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: Advise a non-hormonal or non-enzyme-sensitive contraceptive method such as a copper IUD or a medroxyprogesterone injection. Continue it for several weeks after primidone is stopped.
What other medicines interact with Ethinyl estradiol-levonorgestrel?
MediHelp also lists interactions of Ethinyl estradiol-levonorgestrel with, for example, Fezolinetant, Ombitasvir / paritaprevir / ritonavir and dasabuvir, Tranexamic acid. The full list is on the Ethinyl estradiol-levonorgestrel page.
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