Drug Interaction — ORE Part 1 MCQ

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ModeratePharmacology & TherapeuticsDrug InteractionORE Part 1

A patient on lithium therapy for bipolar disorder requires a dental prescription. Which commonly prescribed dental analgesic should be avoided?

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

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Correct answer: D — Ibuprofen (and other NSAIDs)

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

The correct answer is A: Ibuprofen and other NSAIDs. NSAIDs, including ibuprofen, significantly reduce renal lithium excretion, leading to elevated plasma lithium concentrations and risk of serious toxicity (tremor, confusion, cardiac arrhythmias, acute renal failure). This interaction is well-established in UK NHS lithium safety guidelines and is potentially fatal. NSAIDs should be avoided unless absolutely necessary, in which case lithium levels must be closely monitored. Paracetamol (B), codeine (C), and dihydrocodeine (D) have no clinically significant lithium interactions. Aspirin (E) at analgesic doses does not significantly affect lithium clearance and is not contraindicated. For dental pain control in lithium-treated patients, paracetamol is the safest first-line analgesic.

Reference: HPFT Safe Use of Lithium Guidelines Version 3.0 (January 2024), NHS Hertfordshire Partnership University NHS Foundation Trust. https://www.hpft.nhs.uk/media/7243/safe-use-of-lithium-guidelines-final-jan-2024.pdf