A 65-year-old patient received intravenous fentanyl for procedural sedation during a cardiac catheterisation procedure. He becomes overly sedated with respiratory depression and is given intravenous naloxone. Why must the patient be monitored for at least 2 hours after naloxone administration?
- A Naloxone causes transient hypotension requiring observation
- B Naloxone induces hepatic enzymes that prolong fentanyl metabolism
- C The duration of naloxone is shorter than the respiratory depressant effect of fentanyl ✓
- D Fentanyl undergoes enterohepatic recirculation causing delayed toxicity
Correct answer: C. The duration of naloxone is shorter than the respiratory depressant effect of fentanyl
Explanation
Naloxone has a clinical duration of action of approximately 30 to 60 minutes, whereas the respiratory depressant effect of fentanyl can last for several hours. This mismatch means the opioid effect can outlast the antagonist, leading to rebound respiratory depression once naloxone wears off. Therefore, prolonged monitoring is essential to detect and treat any recurrence of respiratory depression.
Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.
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