Drug interactions
Fluoxetine + St john's wort
Severity: Major
Fluoxetine and St john's wort: major interaction.
Last updated Sources: US FDA label
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 combining it with an SSRI raises the risk of serotonin syndrome. Patients often take it without informing prescribers, so the interaction is easily missed.
What this interaction means in plain words
Fluoxetine and St john's wort 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 serotonergic effects through inhibition of monoamine reuptake.
What to do
Advise patients to stop St John's wort while taking fluoxetine. Monitor for agitation, tremor, sweating and hyperthermia if both have been taken.
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?
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References
Other interactions of Fluoxetine
- Fluoxetine + Isocarboxazid Contraindicated
- Fluoxetine + Mavacamten Contraindicated
- Fluoxetine + Methylene blue Contraindicated
- Fluoxetine + Phenelzine Contraindicated
- Fluoxetine + Pimozide Contraindicated
- Fluoxetine + Rasagiline Contraindicated
Frequently asked questions
Can I take Fluoxetine with St john's wort?
MediHelp rates the interaction as major. Fluoxetine and St john's wort 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 combining it with an SSRI raises the risk of serotonin syndrome. Patients often take it without informing prescribers, so the interaction is easily missed.
How serious is the interaction between Fluoxetine and St john's wort?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Advise patients to stop St John's wort while taking fluoxetine. Monitor for agitation, tremor, sweating and hyperthermia if both have been taken.
What other medicines interact with Fluoxetine?
MediHelp also lists interactions of Fluoxetine with, for example, Isocarboxazid, Mavacamten, Methylene blue. The full list is on the Fluoxetine page.
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