skip to main content

St John's wort interactions — GPhC CRA MCQ

Instant feedback + full explanation. One question, done properly.

HardDrug InteractionsSt John's wort interactionsGPhC CRA

A 39-year-old woman taking sertraline 100mg daily asks whether she can start St John's wort bought online because her mood remains low. She also takes desogestrel and has no other medicines. What is the most important interaction to flag?

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

Reveal the answer and explanation

Correct answer: C — St John's wort can increase serotonergic adverse effects and reduce contraceptive reliability

St John's wort can interact with SSRIs and increase the risk of serotonergic toxicity. It also induces drug metabolism and can reduce the effectiveness of hormonal contraception. The patient should be advised not to start it and to seek review of depression treatment. Products bought online may vary in strength and quality, adding further uncertainty.

Reference: BNF