Naloxone
A competitive opioid receptor antagonist that rapidly reverses opioid-induced respiratory depression and sedation.
On the exam, the trigger is the opioid toxidrome — abnormally slow breathing (often well under 12, sometimes 4–6/min) with pinpoint pupils and a depressed level of consciousness in someone on opioids. The answer almost always pairs naloxone with airway support and ventilation (open the airway, oxygenate/bag-valve-mask first or simultaneously), never naloxone alone. Titrate to adequate breathing, not full alertness, to avoid precipitating violent acute withdrawal. The high-yield “tell” afterward is re-narcotization: because many opioids outlast the antagonist, the right answer is to keep monitoring and re-dose.
The trap with morphine is reflexive reversal: a stable post-op patient who is drowsy but breathing adequately does NOT get naloxone — you hold the next opioid dose instead (reserve naloxone for severe sedation with inadequate respirations). Naloxone reverses opioids only; it does nothing for benzodiazepine sedation (flumazenil) or heparin bleeding (protamine) — don’t grab the wrong antagonist. Memory hook: “Narcan = Narcotics canceled,” but only briefly.
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