M3G Neuroexcitation — FRCA Primary MCQ

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HardPharmacology - AnalgesicsM3G NeuroexcitationFRCA Primary

Morphine-3-glucuronide (M3G) is pharmacologically significant because:

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Correct answer: A — It may cause neuroexcitation including hyperalgesia and myoclonus

M3G has no significant analgesic activity at the mu receptor but may contribute to neuroexcitatory side effects including hyperalgesia / allodynia / and myoclonus particularly when it accumulates in renal failure. M6G is the analgesic metabolite. M3G:M6G ratio is approximately 9:1.

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