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St John's wort and contraception — GPhC CRA MCQ

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EasyDrug InteractionsSt John's wort and contraceptionGPhC CRA

A patient using a combined oral contraceptive asks to buy St John’s wort for low mood. They do not want pregnancy. What is the most important interaction to flag?

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Correct answer: C — St John’s wort can reduce contraceptive effectiveness

St John’s wort is an enzyme inducer and can reduce exposure to hormonal contraceptives, increasing pregnancy risk. It can also interact with antidepressants and many other medicines. The patient should be advised not to use it without clinical advice and to seek support for low mood. Alternative contraception or mood treatment advice may be needed.

Reference: BNF