Drug interactions
Ethinyl estradiol-levonorgestrel + Fosphenytoin
Severity: Major
Ethinyl estradiol-levonorgestrel and Fosphenytoin: major interaction.
Last updated Sources: US FDA label
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
Fosphenytoin is converted to phenytoin, an enzyme inducer that lowers circulating levels of both contraceptive hormones. This can cause breakthrough bleeding and contraceptive failure with unintended pregnancy.
What this interaction means in plain words
Ethinyl estradiol-levonorgestrel and Fosphenytoin 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; Fosphenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4 and other hepatic enzymes, increasing the metabolism of ethinyl estradiol and levonorgestrel.
What to do
Use a non-hormonal or non-enzyme-dependent method such as a copper IUD or levonorgestrel IUD, or add a barrier method. Avoid relying on the combined pill during and for several weeks after treatment.
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 Fosphenytoin
- Dronedarone + Fosphenytoin Contraindicated
- Fosphenytoin + Ledipasvir-sofosbuvir Contraindicated
- Fosphenytoin + Lorlatinib Contraindicated
- Fosphenytoin + Lurasidone Contraindicated
- Fosphenytoin + Ranolazine Contraindicated
- Fosphenytoin + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
Frequently asked questions
Can I take Ethinyl estradiol-levonorgestrel with Fosphenytoin?
MediHelp rates the interaction as major. Ethinyl estradiol-levonorgestrel and Fosphenytoin 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. Fosphenytoin is converted to phenytoin, an enzyme inducer that lowers circulating levels of both contraceptive hormones. This can cause breakthrough bleeding and contraceptive failure with unintended pregnancy.
How serious is the interaction between Ethinyl estradiol-levonorgestrel and Fosphenytoin?
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-hormonal or non-enzyme-dependent method such as a copper IUD or levonorgestrel IUD, or add a barrier method. Avoid relying on the combined pill during and for several weeks after treatment.
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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