Drug interactions
St john's wort + Venlafaxine
Severity: Major
St john's wort and Venlafaxine: major 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 has serotonergic activity, and combined use with venlafaxine increases the risk of serotonin syndrome. Its enzyme-inducing effects may also alter drug concentrations unpredictably.
What this interaction means in plain words
St john's wort and Venlafaxine 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
Additive serotonin reuptake inhibition, with St John's wort also inducing CYP3A4 and P-glycoprotein.
What to do
Avoid the combination and ask patients to stop St John's wort before venlafaxine is started. Monitor for signs of serotonin toxicity if exposure has occurred.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for St john's wort and Venlafaxine, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 14 days on the web. No card needed.
Other interactions of Venlafaxine
- Isocarboxazid + Venlafaxine Contraindicated
- Methylene blue + Venlafaxine Contraindicated
- Phenelzine + Venlafaxine Contraindicated
- Procarbazine + Venlafaxine Contraindicated
- Rasagiline + Venlafaxine Contraindicated
- Safinamide + Venlafaxine Contraindicated
Frequently asked questions
Can I take St john's wort with Venlafaxine?
MediHelp rates the interaction as major. St john's wort and Venlafaxine 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. St John's wort has serotonergic activity, and combined use with venlafaxine increases the risk of serotonin syndrome. Its enzyme-inducing effects may also alter drug concentrations unpredictably.
How serious is the interaction between St john's wort and Venlafaxine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination and ask patients to stop St John's wort before venlafaxine is started. Monitor for signs of serotonin toxicity if exposure has occurred.
What other medicines interact with Venlafaxine?
MediHelp also lists interactions of Venlafaxine with, for example, Isocarboxazid, Methylene blue, Phenelzine. The full list is on the Venlafaxine page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
