Mu-opioid receptor competitive antagonism at the brainstem respiratory center. Agonist molecules occupy receptors and suppress respiratory drive; naloxone competes for and displaces them, restoring breathing until its own short half-life runs out.
Respiratory Rate
— /min
Receptor Occupancy
—%
Naloxone Level
—%
Withdrawal Score
—
Consciousness (GCS)
—
Since Last Naloxone
—
Naloxone Effect Remaining0%
Half-life mismatch: naloxone (~60–90 min) often wears off before long-acting opioids (fentanyl ~2–4h, methadone 8–59h) clear the body — re-narcotization can follow a single bolus. Consider an infusion at ⅔ the effective reversal dose per hour.
Titrate to effect: in opioid-dependent patients, 0.04–0.4mg increments reduce precipitated-withdrawal risk vs. a full 2mg push — reserved for clear life-threatening apnea.