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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 26-year-old woman taking a combined oral contraceptive asks to buy St John's wort for low mood. She does not use condoms and wants to avoid pregnancy. What is the most important interaction to flag?

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Correct answer: E — St John's wort may reduce contraceptive effectiveness

St John's wort induces drug-metabolising enzymes and can reduce the effectiveness of hormonal contraception. This may lead to unintended pregnancy. It can also interact with antidepressants and other medicines. The pharmacist should advise against use and signpost for mood assessment.

Reference: BNF; FSRH