CYP2D6 Codeine Pharmacogenomics — FRCA Primary MCQ

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ModeratePharmacology - General PrinciplesCYP2D6 Codeine PharmacogenomicsFRCA Primary

Regarding pharmacogenomics which cytochrome P450 enzyme is most clinically relevant for codeine metabolism and is subject to significant genetic polymorphism?

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Correct answer: B — CYP2D6

CYP2D6 converts codeine to morphine (its active analgesic form). Poor metabolisers (~7% Caucasians / ~1% Chinese) get minimal analgesia. Ultra-rapid metabolisers (~1-2% Caucasians / ~29% Ethiopians) may produce toxic morphine levels causing respiratory depression and death particularly in children (FDA black box warning for paediatric tonsillectomy).

Reference: Peck Hill Williams 2014 Pharmacology for Anaesthesia and Intensive Care