Bipolar Depression Prevention — MRCPsych Paper B MCQ

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ModerateMood DisordersBipolar Depression PreventionMRCPsych Paper B

A 38-year-old man with bipolar I disorder is euthymic after recovering from a depressive episode. During the previous 6 years, he has experienced four major depressive episodes and one manic episode. No previous maintenance medicine was clearly effective. Which medicine is specifically licensed in the UK to prevent depressive episodes in adults with bipolar I disorder who experience predominantly depressive episodes?

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Correct answer: C — Lamotrigine

Lamotrigine is correct. Its UK SmPC specifically indicates it for preventing depressive episodes in adults with bipolar I disorder whose episodes are predominantly depressive. Maintenance studies found that lamotrigine delayed depressive recurrence compared with placebo, whereas its effect on manic, hypomanic or mixed recurrence was not statistically significant. It is not indicated for acute bipolar depression or mania. Lithium is the most effective long-term treatment for bipolar disorder overall according to NICE and is an important alternative, but it does not have the same depression-polarity-specific indication tested here. Quetiapine has roles in acute bipolar depression and broader maintenance treatment. Valproate and carbamazepine are more associated with antimanic or broader mood-stabilising strategies and do not have this specific UK indication for predominantly depressive bipolar I disorder.

Reference: Electronic Medicines Compendium. Lamotrigine Milpharm 25 mg tablets, Summary of Product Characteristics, sections 4.1 and 5.1; revised 12 May 2026. https://www.medicines.org.uk/emc/product/4736/smpc