Naloxone is a pure opioid receptor antagonist that reverses opioid overdose by displacing opioids from their receptors, restoring respiratory drive and level of consciousness. It is most commonly administered by EMT-Basics via the intranasal route; for example, Narcan Nasal Spray delivers 4 mg per spray, typically one spray per nostril, and naloxone can also be given intramuscularly, including via auto-injector devices such as Evzio. The indication for naloxone is suspected opioid overdose with respiratory depression, classically marked by pinpoint pupils (miosis), decreased level of consciousness, and slow or absent breathing.
The priority in any suspected opioid overdose is airway and ventilatory support, because naloxone does not replace the need for oxygenation. The EMT should provide bag-valve-mask ventilation as needed while preparing to administer naloxone. Intranasal naloxone typically takes effect within 2 to 5 minutes. Because naloxone's duration of action is shorter than that of many opioids, particularly long-acting ones such as methadone, re-sedation can occur, and repeat doses along with continued ventilatory support may be required.
Naloxone has minimal contraindications; the only notable one is rare hypersensitivity. It is considered very safe even when given to a patient whose overdose turns out not to be opioid-related. In opioid-dependent patients, however, the sudden reversal can precipitate acute withdrawal, producing agitation, nausea, vomiting, or combativeness as consciousness returns. EMTs should anticipate this response, continue to manage the airway, and transport the patient for further evaluation. Naloxone has no effect on overdoses from benzodiazepines, stimulants, or other non-opioid agents.