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Suspected lithium toxicity during intercurrent gastrointestinal illness — MSRA MCQ

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Hardall topics relevant for this examSuspected lithium toxicity during intercurrent gastrointestinal illnessMSRA

A 58-year-old man with bipolar disorder takes lithium carbonate MR 800 mg nocte. His lithium concentration was 0.72 mmol/L and eGFR 78 mL/min/1.73 m² 6 weeks ago. He takes ramipril for hypertension. He presents with 3 days of vomiting and profuse diarrhoea after a presumed viral gastroenteritis. He has continued his usual medication and has taken over-the-counter ibuprofen 400 mg three times daily for myalgia. Today he reports worsening lethargy, a new coarse hand tremor and unsteadiness when turning. He is afebrile, alert and orientated, with BP 108/66 mmHg and dry mucous membranes. His last lithium dose was 4 hours ago. What is the most appropriate immediate management in primary care?

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Correct answer: C — Withhold lithium, arrange urgent serum lithium concentration and U&Es, and seek same-day specialist advice

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

This is suspected lithium toxicity. Gastrointestinal fluid and sodium loss can reduce lithium clearance; ramipril and ibuprofen further increase the risk of lithium accumulation. The new coarse tremor, lethargy and gait unsteadiness are compatible with neurological toxicity. A routine 12-hour trough sample is appropriate for stable therapeutic monitoring, but suspected toxicity requires urgent assessment irrespective of the interval since the last dose. Lithium should therefore be withheld immediately, with urgent lithium concentration and U&Es, and same-day specialist advice. The need for emergency secondary-care referral is then determined by symptom severity, biochemical results and clinical evolution. B is unsafe because symptomatic toxicity should not await recovery or routine testing. C is initially attractive because trough sampling standardises lithium monitoring, but it wrongly continues lithium and delays assessment. D is inappropriate because dose reduction is not a response to possible acute toxicity; lithium should be withheld pending urgent review. E addresses one contributor, ibuprofen, but continuing lithium despite dehydration, interacting drugs and neurological features risks progression of toxicity.

Reference: Lithium monitoring – NHS Specialist Pharmacy Service (Accessed 15 August 2026) — https://www.sps.nhs.uk/monitorings/lithium-monitoring/ Lithium monitoring – NHS Specialist Pharmacy Service (Accessed 15 August 2026) — https://www.sps.nhs.uk/monitorings/lithium-monitoring/ Lithium Carbonate Essential Pharma 250 mg film-coated tablets – Summary of Product Characteristics (Last updated 21 January 2025) — https://www.medicines.org.uk/emc/product/10828/smpc