Drug interactions
Sildenafil + St john's wort
Severity: Moderate
Sildenafil 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 P-glycoprotein, which can reduce sildenafil exposure and its therapeutic effect. Effects persist for some time after the herb is stopped.
What this interaction means in plain words
Sildenafil 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
Hyperforin in St John's wort activates PXR, inducing CYP3A4 and efflux transporters.
What to do
Advise patients to avoid St John's wort, particularly with sildenafil for pulmonary hypertension. Monitor response if it cannot be stopped.
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 Sildenafil
- Amyl nitrite + Sildenafil Contraindicated
- Atazanavir + Sildenafil Contraindicated
- Cobicistat + Sildenafil Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Sildenafil Contraindicated
- Glyceryl trinitrate pr + Sildenafil Contraindicated
- Isosorbide dinitrate + Sildenafil Contraindicated
Frequently asked questions
Can I take Sildenafil with St john's wort?
MediHelp rates the interaction as moderate. Sildenafil 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 P-glycoprotein, which can reduce sildenafil exposure and its therapeutic effect. Effects persist for some time after the herb is stopped.
How serious is the interaction between Sildenafil 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, particularly with sildenafil for pulmonary hypertension. Monitor response if it cannot be stopped.
What other medicines interact with Sildenafil?
MediHelp also lists interactions of Sildenafil with, for example, Amyl nitrite, Atazanavir, Cobicistat. The full list is on the Sildenafil page.
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