Opioid analgesic
Fentanyl
Sublimaze Opioid — blue 50 mcg/mL
Fast, potent, short-acting (after a single dose) analgesia — about 100× morphine.
Typical adult doses
| Indication | Dose | Onset | Duration |
|---|---|---|---|
| Analgesia | 0.5–1 mcg/kg increments (commonly 25–100 mcg) | 1–2 min (peak 3–5) | 30–60 min |
| Induction adjunct | 1–2 mcg/kg IV (higher in cardiac anesthesia) | — | — |
Mechanism
Mu-opioid receptor agonist.
Key effects
- Analgesia, blunts the response to laryngoscopy
- Respiratory depression
- Bradycardia
Watch out for
- Chest-wall rigidity with rapid high doses (treated by the team with NMB + ventilation)
- PONV, pruritus
- Context-sensitive half-time rises with infusions
Reversal
Naloxone 0.04 mg (40 mcg) IV increments every 2–3 min, titrated to breathing. A full 0.4 mg can cause severe pain, hypertension and pulmonary edema. Naloxone may wear off first (renarcotization).
Pimp questions
Pimp question 1
Why does fentanyl cause chest-wall rigidity, and what fixes it?
Answer
Central mu-opioid effects increase muscle tone with rapid, high doses; the team treats it with a neuromuscular blocker and ventilation.
Pimp question 2
Why can a “short-acting” fentanyl infusion wake up slowly?
Answer
Its context-sensitive half-time rises with duration as tissue stores saturate.