Lithium Monitoring — MRCPsych Paper B MCQ

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EasyMood DisordersLithium MonitoringMRCPsych Paper B

A 35-year-old woman with bipolar I disorder is prescribed lithium for the first time as long-term prophylaxis. According to NICE CG185, what plasma lithium concentration should initially be aimed for once treatment is titrated?

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Correct answer: C — 0.6–0.8 mmol/L

Explanation lettering: D = shown as A · E = shown as B · A = shown as D · B = shown as E

C is correct. NICE CG185 recommends aiming for a plasma lithium concentration of 0.6–0.8 mmol/L when lithium is prescribed for the first time. Concentrations below 0.6 mmol/L, represented by options A and B, are below the recommended therapeutic range. Option D is not the routine initial target: 0.8–1.0 mmol/L may be considered for a trial of at least 6 months when a person has previously relapsed while taking lithium or has subthreshold symptoms causing functional impairment. Option E exceeds the target ranges recommended by CG185 and would increase concern about adverse effects and toxicity. Lithium levels should be checked 1 week after initiation and after each dose change, then weekly until stable.

Reference: National Institute for Health and Care Excellence. Bipolar disorder: assessment and management (CG185), recommendations 1.10.15–1.10.16. Updated 2025. https://www.nice.org.uk/guidance/cg185/chapter/Recommendations