Naloxone / Narcan

A patient on morphine stops breathing at 6 respirations per minute. You have naloxone at the bedside — but pushing it too fast can be more dangerous than the overdose itself.

Naloxone is a pure opioid antagonist that competitively displaces opioids from mu, kappa, and delta receptors without activating them. It reverses respiratory depression, sedation, and hypotension caused by opioid overdose. IV onset is 1–2 minutes; IM/subcutaneous onset is 2–5 minutes; intranasal onset is approximately 3–5 minutes. The critical problem: naloxone's duration of action (30–90 minutes) is shorter than most opioids it reverses. This means the patient can re-sedate and stop breathing again once naloxone wears off — called renarcotization. After administration, continuous respiratory monitoring for at least 2 hours is mandatory, longer for long-acting opioids like methadone. The dose is titrated in small increments (0.04–0.4 mg IV) to restore respirations without fully reversing analgesia. Giving the entire dose as a rapid bolus can precipitate acute opioid withdrawal — severe pain, hypertension, tachycardia, pulmonary edema, and even cardiac arrest. The goal is a respiratory rate above 12, not a fully alert patient.

Key Distinctions

Don't confuse the goal of naloxone (restore respirations ≥12) with complete reversal of all opioid effects — full reversal causes dangerous withdrawal. Students mix up naloxone (opioid antagonist, reversal agent) with naltrexone (oral opioid antagonist used for long-term addiction maintenance, much longer duration). Renarcotization is the most tested safety concept: the opioid outlasts the naloxone, so monitoring must continue well beyond the initial response.

Clinical Pearl

Titrate to breathe, not to wake. Respiratory rate ≥12 is your target — a drowsy but breathing patient is safer than one in full withdrawal.