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Recurrent methadone-induced respiratory depression — MRCEM SBA MCQ

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HardToxicology and environmental emergenciesRecurrent methadone-induced respiratory depressionMRCEM SBA

A 44-year-old man who takes methadone daily for opioid dependence is brought to the emergency department after taking an additional, unknown quantity of methadone. On arrival, he is barely rousable and breathing six times per minute. His airway is supported and intravenous naloxone is titrated until he breathes 14 times per minute. He remains drowsy but rouses to voice and protects his airway. Twice over the next hour, his respiratory rate falls to six times per minute and improves promptly after a further intravenous naloxone bolus. After the second bolus, he is again breathing adequately and maintaining his airway. Which management plan is most appropriate now?

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

Reveal the answer and explanation

Correct answer: A — Begin a naloxone infusion titrated to adequate ventilation and admit for monitored observation.

The initial response to naloxone identifies a substantial opioid-mediated component to his respiratory depression. Methadone can act longer than naloxone, and two episodes of recurrent bradypnoea show that intermittent reversal has not provided sustained ventilation. A titrated intravenous infusion is therefore preferable, with close monitoring and admission; airway support must remain available if ventilation deteriorates. ([sps.nhs.uk](https://sps.nhs.uk/articles/reversing-an-adult-opioid-overdose-with-naloxone/)) B is initially attractive because each bolus works, but repeated respiratory depression after a long-acting opioid favours an infusion rather than waiting for the next episode. C selects the right route but the wrong endpoint: he already protects his airway, and naloxone should be titrated to reverse dangerous respiratory depression, not to make an opioid-dependent patient fully alert. Excessive reversal risks acute withdrawal. ([sps.nhs.uk](https://sps.nhs.uk/articles/reversing-an-adult-opioid-overdose-with-naloxone/)) D would be reasonable after sustained recovery, but not following two documented recurrences. E mistakes a period of improvement after naloxone for resolution of methadone toxicity. Observation for recurrence is required after naloxone is stopped; four normal hours cannot justify discharge while recurrent toxicity still requires treatment. ([sps.nhs.uk](https://sps.nhs.uk/articles/reversing-an-adult-opioid-overdose-with-naloxone/))

Reference: Reversing an adult opioid overdose with naloxone (Updated 13 March 2026) — https://sps.nhs.uk/articles/reversing-an-adult-opioid-overdose-with-naloxone/ Naloxone 400 micrograms/ml solution for Injection/Infusion: Summary of Product Characteristics (Current product information; checked 27 September 2026) — https://www.medicines.org.uk/emc/product/6344/smpc