Drug interactions
Etonogestrel + Phenobarbital
Severity: Major
Etonogestrel and Phenobarbital: 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
Phenobarbital is a strong enzyme inducer and can reduce circulating etonogestrel, leading to contraceptive failure with the implant or ring. Pregnancy risk is the main concern, particularly because some antiepileptics are teratogenic.
What this interaction means in plain words
Etonogestrel and Phenobarbital 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
Phenobarbital induces CYP3A4, accelerating etonogestrel clearance.
What to do
Prefer a non-hormonal method or a method not affected by induction, such as a copper IUD or levonorgestrel IUD. If etonogestrel is used, add condoms and continue for several weeks after stopping the inducer.
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 Etonogestrel
Frequently asked questions
Can I take Etonogestrel with Phenobarbital?
MediHelp rates the interaction as major. Etonogestrel and Phenobarbital 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. Phenobarbital is a strong enzyme inducer and can reduce circulating etonogestrel, leading to contraceptive failure with the implant or ring. Pregnancy risk is the main concern, particularly because some antiepileptics are teratogenic.
How serious is the interaction between Etonogestrel and Phenobarbital?
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 non-hormonal method or a method not affected by induction, such as a copper IUD or levonorgestrel IUD. If etonogestrel is used, add condoms and continue for several weeks after stopping the inducer.
What other medicines interact with Etonogestrel?
MediHelp also lists interactions of Etonogestrel with, for example, Amobarbital, Armodafinil, Bosentan. The full list is on the Etonogestrel page.
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