Irinotecan and St Johns Wort: Drug Interaction Guide
Quick answer: This is a major interaction — avoid combining Irinotecan and St Johns Wort unless specifically directed by your doctor.
How Irinotecan interacts with St Johns Wort
St John's wort induces CYP3A4 and UGT1A1, increasing metabolism of the active SN-38 metabolite of irinotecan and reducing antitumour efficacy.
What you should do
St John's wort is contraindicated during irinotecan therapy and should be stopped at least 2 weeks before chemotherapy.
Key facts
Severity
Major — avoid combination
Mechanism
St John's wort induces CYP3A4 and UGT1A1, increasing metabolism of the active SN-38 metabolite of irinotecan and reducin...
Action
St John's wort is contraindicated during irinotecan therapy and should be stopped at least 2 weeks before chemotherapy.
Frequently asked questions
Can I take Irinotecan and St Johns Wort together?
No — this combination should generally be avoided. St John's wort is contraindicated during irinotecan therapy and should be stopped at least 2 weeks before chemotherapy.
What is the severity of this interaction?
The interaction between Irinotecan and St Johns Wort is classified as Major — avoid combination. St John's wort induces CYP3A4 and UGT1A1, increasing metabolism of the active SN-38 metabolite of irinotecan and reducing antitumour efficacy.
What should I do if I'm prescribed both?
St John's wort is contraindicated during irinotecan therapy and should be stopped at least 2 weeks before chemotherapy. Always consult your prescribing clinician — do not stop or change medications without medical guidance.
Last reviewed: by iMedic Medical Editorial Team. Our editorial process.