Drug interactions
Ondansetron + St john's wort
Severity: Minor
Ondansetron and St john's wort: minor 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 may reduce ondansetron concentrations. This could weaken antiemetic efficacy, though evidence specific to ondansetron is limited.
What this interaction means in plain words
Ondansetron and St john's wort have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Why it happens
Induction of CYP3A4 and P-gp by St John's wort increases ondansetron clearance.
What to do
Monitor antiemetic response and consider stopping the herbal product or adjusting antiemetic therapy if control is poor.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Ondansetron
- Apomorphine + Ondansetron Contraindicated
- Ondansetron + Thioridazine Contraindicated
- Ondansetron + Vandetanib Contraindicated
- Adagrasib + Ondansetron Major
- Amiodarone + Ondansetron Major
- Amisulpride + Ondansetron Major
Frequently asked questions
Can I take Ondansetron with St john's wort?
MediHelp rates the interaction as minor. Ondansetron and St john's wort have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. St John's wort induces CYP3A4 and P-glycoprotein and may reduce ondansetron concentrations. This could weaken antiemetic efficacy, though evidence specific to ondansetron is limited.
How serious is the interaction between Ondansetron and St john's wort?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor antiemetic response and consider stopping the herbal product or adjusting antiemetic therapy if control is poor.
What other medicines interact with Ondansetron?
MediHelp also lists interactions of Ondansetron with, for example, Apomorphine, Thioridazine, Vandetanib. The full list is on the Ondansetron page.
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