Drug Interactions — MRCPsych Paper B MCQ

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

ModerateMood DisordersDrug InteractionsMRCPsych Paper B

A 70-year-old woman has a moderate depressive episode for which antidepressant medication is indicated. She takes warfarin for atrial fibrillation and has no other contraindication to the drugs listed. Which antidepressant is most appropriate to consider specifically because she is taking warfarin?

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

Reveal the answer and explanation

Correct answer: E — Mirtazapine

The correct answer is **mirtazapine**. NICE advises that SSRIs should not normally be offered with warfarin because serotonin-mediated platelet dysfunction increases bleeding risk. It specifically recommends considering mirtazapine in patients taking warfarin. Mirtazapine can nevertheless cause a small increase in INR, so INR should be monitored after it is started, stopped or substantially dose-adjusted. Sertraline and citalopram have relatively low CYP-mediated interaction potential, but this does not remove the pharmacodynamic bleeding risk shared by SSRIs; therefore neither is the best answer here. Fluoxetine has greater CYP interaction potential and a long half-life. Venlafaxine is also serotonergic and is not the NICE-recommended alternative for this interaction.

Reference: National Institute for Health and Care Excellence. Depression in adults with a chronic physical health problem: recognition and management (CG91), recommendations 1.5.2.8 and 1.5.2.11. Published 2009; last reviewed 2024. https://www.nice.org.uk/guidance/cg91/chapter/Recommendations