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Opioid toxicity in CKD — ESENeph MCQ

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ModerateTherapeutics and Safe PrescribingOpioid toxicity in CKDESENeph

A 63-year-old man with CKD G4 takes morphine modified-release for chronic back pain. He becomes drowsy with myoclonus after a dose increase; eGFR is 22 mL/min/1.73 m². There is no hypercalcaemia, infection or stroke. What is the most likely underlying cause?

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Correct answer: B — Accumulation of renally cleared morphine metabolites

Morphine metabolites accumulate in advanced CKD and can cause sedation, confusion and myoclonus. Opioid withdrawal causes agitation, diarrhoea and autonomic symptoms rather than drowsiness after dose escalation. Calcineurin toxicity requires exposure to a calcineurin inhibitor. The pearl is that analgesic choice in CKD should consider active metabolites, dosing interval and non-opioid harms such as NSAID nephrotoxicity.

Reference: BNF renal impairment prescribing guidance; NICE NG203