Drug interactions
Simvastatin + St john's wort
Severity: Moderate
Simvastatin 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 and has been shown to lower simvastatin acid concentrations. This may reduce cholesterol-lowering efficacy.
What this interaction means in plain words
Simvastatin 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 intestinal and hepatic CYP3A4 (via PXR activation) by hyperforin increases simvastatin clearance.
What to do
Advise patients to avoid St John's wort, or monitor lipid levels and consider a non-CYP3A4-dependent statin if it is continued.
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 Simvastatin
- Atazanavir + Simvastatin Contraindicated
- Clarithromycin + Simvastatin Contraindicated
- Cobicistat + Simvastatin Contraindicated
- Cyclosporine + Simvastatin Contraindicated
- Cyclosporin + Simvastatin Contraindicated
- Danazol + Simvastatin Contraindicated
Frequently asked questions
Can I take Simvastatin with St john's wort?
MediHelp rates the interaction as moderate. Simvastatin 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 and has been shown to lower simvastatin acid concentrations. This may reduce cholesterol-lowering efficacy.
How serious is the interaction between Simvastatin 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 lipid levels and consider a non-CYP3A4-dependent statin if it is continued.
What other medicines interact with Simvastatin?
MediHelp also lists interactions of Simvastatin with, for example, Atazanavir, Clarithromycin, Cobicistat. The full list is on the Simvastatin page.
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