Drug interactions
Finasteride + St john's wort
Severity: Moderate
Finasteride and St john's wort: 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
St John's wort induces CYP3A4 and may reduce finasteride exposure, possibly blunting its therapeutic effect.
What this interaction means in plain words
Finasteride and St john's wort 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 (via PXR activation) by St John's wort increases finasteride metabolism.
What to do
Advise patients to avoid St John's wort or monitor for loss of finasteride effect.
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 Finasteride
- Finasteride + Levoketoconazole Moderate
- Finasteride + Nefazodone Moderate
- Finasteride + Rifampin Moderate
- Amobarbital + Finasteride Minor
- Aprepitant + Finasteride Minor
- Armodafinil + Finasteride Minor
Frequently asked questions
Can I take Finasteride with St john's wort?
MediHelp rates the interaction as moderate. Finasteride and St john's wort 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. St John's wort induces CYP3A4 and may reduce finasteride exposure, possibly blunting its therapeutic effect.
How serious is the interaction between Finasteride and St john's wort?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Advise patients to avoid St John's wort or monitor for loss of finasteride effect.
What other medicines interact with Finasteride?
MediHelp also lists interactions of Finasteride with, for example, Levoketoconazole, Nefazodone, Rifampin. The full list is on the Finasteride page.
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