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NSAID-associated lithium toxicity — SCE Geriatric Medicine MCQ

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HardNSAIDsNSAID-associated lithium toxicitySCE Geriatric Medicine

An 81-year-old woman with bipolar I disorder has taken modified-release lithium carbonate for 18 years. Her mood is stable, and her usual 12-hour plasma lithium concentration is 0.62 mmol/L. She has chronic kidney disease stage 3a, with a baseline eGFR of 47 mL/min/1.73 m². Six days ago, she developed an exacerbation of knee osteoarthritis and began taking over-the-counter ibuprofen 400 mg three times daily. Over the same period, she has had diarrhoea and reduced oral intake but continued her lithium. She now presents after two falls with confusion, dysarthria, a coarse tremor and marked gait ataxia. Her blood pressure is 108/64 mmHg. Investigations show a 12-hour plasma lithium concentration of 1.32 mmol/L, sodium 133 mmol/L and eGFR 31 mL/min/1.73 m². Which is the most appropriate immediate management?

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Correct answer: C — Withhold lithium and ibuprofen and arrange urgent hospital assessment for lithium toxicity

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

This is symptomatic lithium toxicity precipitated by the combination of ibuprofen, volume depletion and deteriorating renal function. NSAIDs inhibit renal prostaglandin synthesis and can reduce renal lithium clearance. Diarrhoea and reduced intake further increase proximal sodium and lithium reabsorption, while her age and chronic kidney disease reduce physiological reserve. The lithium concentration is below the approximate 1.5 mmol/L threshold commonly associated with toxicity, but this does not exclude clinically important toxicity. Her coarse tremor, dysarthria, ataxia, confusion and falls are characteristic, and the acute fall in eGFR increases the risk of further accumulation. Lithium and ibuprofen should therefore be withheld, with urgent secondary-care assessment, repeat lithium and electrolyte measurements, fluid-status assessment and specialist toxicology or renal advice as indicated. B is unsafe because symptomatic toxicity requires lithium to be withheld even when the measured concentration appears only moderately elevated. C similarly undertreats established toxicity; dose reduction is not an adequate immediate response. D removes lithium but perpetuates the interaction and renal insult; a proton-pump inhibitor reduces upper gastrointestinal risk but does not prevent NSAID-mediated renal effects. E confuses emergency management with elective lithium withdrawal: gradual tapering reduces relapse risk when lithium is being discontinued routinely, but lithium should be stopped immediately when toxicity is suspected.

Reference: Bipolar disorder: assessment and management (CG185) — Recommendations 1.10.17-1.10.18 (Published 24 September 2014; updated 21 December 2023) — https://www.nice.org.uk/guidance/cg185/chapter/recommendations Lithium monitoring — Abnormal results: risk of toxicity (Updated 6 December 2024) — https://sps.nhs.uk/monitorings/lithium-monitoring/ Ibuprofen 600 mg film-coated tablets — Summary of Product Characteristics (Updated 1 July 2026) — https://www.medicines.org.uk/emc/product/7021/smpc