skip to main content

Morphine renal active metabolites — FRCA Primary MCQ

Instant feedback + full explanation. One question, done properly.

HardPharmacologyMorphine renal active metabolitesFRCA Primary

An elderly patient with eGFR 18 mL/min becomes increasingly sedated overnight after repeated morphine boluses for fractured ribs. Respiratory rate is 7/min and pupils are small. Which pharmacological feature is most relevant?

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

Reveal the answer and explanation

Correct answer: A — Accumulation of active glucuronide metabolites

Morphine-6-glucuronide is pharmacologically active and accumulates in renal impairment, increasing opioid effect and respiratory depression. Plasma cholinesterase is not involved in morphine metabolism. Naloxone can reverse toxicity but may wear off before accumulated opioid effect resolves. Renal function should influence opioid choice and dosing in older patients.

Reference: Peck, Hill & Williams Pharmacology for Anaesthesia and Intensive Care