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St John's wort and combined pill — GPhC CRA MCQ

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ModerateDrug InteractionsSt John's wort and combined pillGPhC CRA

A woman using a combined oral contraceptive asks to buy St John's wort for low mood. She does not want to become pregnant. What is the most important interaction to flag?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: C — Reduced contraceptive efficacy due to enzyme induction

St John's wort induces drug metabolism and can reduce hormonal contraceptive effectiveness. The best answer addresses the key safety, legal or pharmaceutical care issue in the vignette. The other options would either delay appropriate care, create a new risk, or fail to resolve the issue. This is consistent with the cited UK reference for safe pharmacy practice.

Reference: BNF