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St John's wort and oral contraception — GPhC CRA MCQ

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ModerateDrug InteractionsSt John's wort and oral contraceptionGPhC CRA

A woman using a combined oral contraceptive asks to buy St John's wort for low mood. She wants a natural product because she dislikes tablets. What is the most important interaction to flag?

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Correct answer: D — St John's wort can reduce contraceptive efficacy through enzyme induction

St John's wort induces drug-metabolising enzymes and can reduce the effectiveness of hormonal contraception and several other medicines. Patients should be counselled that herbal products can have clinically important interactions. Alternative support for low mood should be discussed.

Reference: BNF; MEP