Opioid overdose and toxicity

Also known as Opioid intoxication · Naloxone reversal · Fentanyl toxicity · Opioid-induced respiratory depression

Opioid overdose causes respiratory depression (medullary respiratory centre depression), miosis (pinpoint pupils), and decreased level of consciousness — the classic triad. Fentanyl is about 100 times more potent than morphine and increasingly implicated in overdose deaths. Management: naloxone (opioid receptor antagonist) — titrate to respiratory rate (NOT full alertness). Avoid precipitating acute withdrawal in chronic users. Long-acting opioids (methadone, fentanyl patches) require prolonged monitoring or naloxone infusion. Non-cardiogenic pulmonary oedema can occur after naloxone reversal.

medium14 referencesUpdated 19 Aug 202612 min readSource-verified · Oct 2026

Checked against its sources on 14 Oct 2026

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8 MCQs

The one-line answer

Opioid overdose is the triad of respiratory depression, miosis and a falling level of consciousness — and the antidote is naloxone, titrated to restore breathing, never to wakefulness. The lethal mechanism is medullary respiratory-centre depression: the patient stops responding to a rising CO2 and stops breathing. Titrate naloxone to response after initial intravenous doses of 0.4 to 2 mg — 0.4 to 0.8 mg usually restores breathing after heroin overdose — going as low as 0.04 mg where precipitating withdrawal is the greater danger (low-dose naloxone with titration is the prudent approach in opioid-dependent patients).^[13] Naloxone is rapidly eliminated (half-life 60 to 120 minutes; a 1 mg IV bolus acts for about 2 hours), so re-sedation is the rule and long-acting agents need an infusion. Remove every fentanyl patch, and watch for non-cardiogenic pulmonary oedema after reversal.^[1]

Meet the patient

An older adult on sustained-release oxycodone and a methadone program is found unconscious — profoundly slow breathing, pinpoint 1 mm pupils, coma. Two empty blister packs and an empty methadone bottle lie beside him. The first move is bag-valve-mask ventilation, because airway and breathing come before the antidote; the second is naloxone titrated to his breathing, not his brain.^[3]

The two decisions that decide the next twelve hours are the two that decide every opioid overdose: have I reversed the ventilation enough to keep him alive? and will it last? Methadone is a long-acting opioid that far outlasts naloxone, whose elimination half-life is 60 to 120 minutes. So he gets an infusion, not a bolus and a wave goodbye. Hold that mismatch and the whole topic slots into place.^[1]

References14Show

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