Drug interactions
Levonorgestrel + Phenobarbital
Severity: Moderate
Levonorgestrel and Phenobarbital: moderate 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
Phenobarbital is an enzyme inducer that lowers levonorgestrel exposure and may cause contraceptive failure. The risk is clearest with oral and emergency use and with long-term phenobarbital therapy.
What this interaction means in plain words
Levonorgestrel and Phenobarbital can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Why it happens
Induction of CYP3A4 by phenobarbital increases levonorgestrel clearance.
What to do
Use a non-hormonal or additional barrier method during therapy and for several weeks after stopping. For emergency contraception, consider a copper IUD.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Levonorgestrel
Frequently asked questions
Can I take Levonorgestrel with Phenobarbital?
MediHelp rates the interaction as moderate. Levonorgestrel and Phenobarbital can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Phenobarbital is an enzyme inducer that lowers levonorgestrel exposure and may cause contraceptive failure. The risk is clearest with oral and emergency use and with long-term phenobarbital therapy.
How serious is the interaction between Levonorgestrel and Phenobarbital?
MediHelp rates it moderate, 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 additional barrier method during therapy and for several weeks after stopping. For emergency contraception, consider a copper IUD.
What other medicines interact with Levonorgestrel?
MediHelp also lists interactions of Levonorgestrel with, for example, Amobarbital, Apalutamide, Belzutifan. The full list is on the Levonorgestrel page.
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