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St John's wort — DFSRH MCQ

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ModeratePharmacologySt John's wortDFSRH

A 35-year-old woman using the implant starts St John’s wort for low mood bought over the counter. She asks if it matters. What would you advise this patient?

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Correct answer: D — St John’s wort may reduce implant effectiveness and should be avoided

St John’s wort is an enzyme inducer and can reduce effectiveness of some hormonal contraception, including implants. Over-the-counter status does not mean interaction-free. Medication history should include herbal products.

Reference: BNF; FSRH Drug Interactions with Hormonal Contraception Guidance; UKMEC 2025