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St John's wort and combined hormonal contraception — GPhC CRA MCQ

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ModerateDrug InteractionsSt John's wort and combined hormonal contraceptionGPhC CRA

A patient taking 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 — St John's wort can reduce contraceptive effectiveness

St John's wort induces drug-metabolising enzymes and can reduce the effectiveness of hormonal contraception. It also interacts with many antidepressants and other medicines, so referral for low mood support is appropriate. The other options either delay appropriate care, use an unsuitable medicine, or miss the main safety issue.

Reference: BNF; FSRH guidance