A 26-year-old man found unconscious with respiratory rate 5/min receives one dose of IV naloxone and regains consciousness with adequate breathing. Twenty minutes later in the ward he again becomes drowsy with respiratory rate 7/min despite no further opioid intake. What is the most likely explanation?
- A He secretly consumed more opioid in the ward
- B He developed acute tolerance to naloxone
- C Naloxone's duration of action is shorter than that of most opioids, causing renarcotization ✓
- D Naloxone undergoes enterohepatic recirculation causing delayed toxicity
Correct answer: C. Naloxone's duration of action is shorter than that of most opioids, causing renarcotization
Explanation
Naloxone has a plasma half-life of roughly 30 to 80 minutes, much shorter than most opioids including heroin metabolites, methadone, and oxycodone. After a single bolus wears off, residual opioid reoccupies mu receptors and respiratory depression returns, called renarcotization. Management requires repeat boluses followed by a continuous infusion titrated to respiration. Secret intake and tolerance to naloxone are not recognized mechanisms here.
Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.
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Written and medically reviewed by the StethoPrep medical team.