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Morphine histamine release — FRCA Primary MCQ

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ModeratePharmacologyMorphine histamine releaseFRCA Primary

After intravenous opioid analgesia, a patient develops flushing, pruritus and mild hypotension without wheeze or airway swelling. Which drug is most likely responsible?

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

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Correct answer: A — Morphine

Morphine can cause dose-related non-IgE histamine release, producing flushing, pruritus and hypotension without true anaphylaxis. Dobutamine is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Dantrolene is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Mannitol is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Bupivacaine is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. In Primary FRCA pharmacology, link the clinical effect to the receptor, distribution or elimination mechanism rather than memorising isolated facts.

Reference: Peck, Hill & Williams Pharmacology for Anaesthesia and Intensive Care; BNF; Primary FRCA textbooks