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Suspected lithium toxicity precipitated by dehydration, CKD and NSAID exposure — MSRA MCQ

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Hardall topics relevant for this examSuspected lithium toxicity precipitated by dehydration, CKD and NSAID exposureMSRA

A 68-year-old man with bipolar disorder is reviewed urgently in general practice. He has taken lithium carbonate MR 800 mg nightly for 4 years; his most recent 12-hour trough lithium concentration, measured 6 weeks ago, was 0.76 mmol/L. He also has CKD G3a and hypertension treated with ramipril. He has had profuse diarrhoea and poor oral intake for 3 days. For worsening knee pain, he started taking over-the-counter ibuprofen 400 mg three times daily 4 days ago. His wife reports that since this morning he has become increasingly drowsy, unsteady when walking and has developed slurred speech. He has a coarse bilateral hand tremor and is intermittently confused. His temperature is 36.7°C, blood pressure 118/70 mmHg, pulse 88 beats/minute and oxygen saturation 98% on air. What is the most appropriate immediate management?

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

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Correct answer: A — Withhold lithium, obtain urgent serum lithium and urea-and-electrolyte tests, and seek immediate specialist advice with same-day acute clinical assessment

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

This presentation is strongly suggestive of lithium toxicity. Diarrhoea and poor intake cause volume depletion, reducing renal lithium clearance; CKD G3a further increases susceptibility. Recent regular ibuprofen is an additional important precipitant because NSAIDs can increase lithium concentrations. Coarse tremor, ataxia, dysarthria, drowsiness and confusion are characteristic neurotoxic features. Lithium must be withheld immediately. An urgent lithium concentration and urea-and-electrolyte assessment are required, alongside immediate specialist advice and same-day acute assessment because he has evolving neurological toxicity. Management must be based on the clinical syndrome rather than awaiting a level alone: toxicity can occur even at an apparently therapeutic serum lithium concentration. A is inappropriate because this is not a routine monitoring scenario and neurological features require urgent action. B wrongly continues lithium while toxicity is suspected. C is inappropriate because dose reduction is not adequate initial management of suspected toxicity. D correctly withholds lithium but delays essential investigations and escalation despite confusion, dysarthria and ataxia.

Reference: NHS Specialist Pharmacy Service: Lithium monitoring (Last updated 6 December 2024) — https://www.sps.nhs.uk/monitorings/lithium-monitoring/ NICE CG185: Bipolar disorder: assessment and management (2014, current recommendations checked August 2026) — https://www.nice.org.uk/guidance/cg185/chapter/recommendations