Fentanyl
Sublimaze (IV) / Duragesic (patch) / Actiq (lozenge)
sedativeIV · transdermal patch · transmucosal · IN · epidural/ITOnset: 1–2 minutes (IV)Duration: 30–60 minutes (single dose); prolonged with infusion
Mechanism of Action
Synthetic opioid. Binds mu-opioid receptors in CNS and periphery → analgesia via decreased pain signal transmission, altered pain perception. Also produces sedation, euphoria, respiratory depression, and GI effects.
Dosing
Adult
ICU analgesia: 25–200 mcg/hr continuous infusion. Bolus: 25–100 mcg IV PRN. Procedural: 1–2 mcg/kg IV
Pediatric
0.5–2 mcg/kg IV bolus; 1–5 mcg/kg/hr infusion
Indications
- Analgesia in mechanically ventilated patients
- Procedural pain management
- Adjunct to sedation in ICU (analgesia-first approach)
- Acute pain management
Contraindications
- Hypersensitivity to fentanyl
- MAOIs within 14 days (risk of serotonin syndrome)
- Severe respiratory depression in non-monitored setting
Side Effects
- Respiratory depression (most critical)
- Chest wall rigidity ('wooden chest') — rapid IV boluses at high doses
- Constipation (prolonged use)
- Hypotension (less than morphine)
- Urinary retention
- Pruritis (less than morphine)
- Tolerance and dependence (prolonged use)
Monitoring Parameters
- Respiratory rate and SpO2
- CPOT or NRS pain scale
- Level of sedation (RASS)
- GI motility (constipation)
- Signs of withdrawal with abrupt discontinuation
Drug Interactions
- CNS depressants (potentiated respiratory depression)
- MAOIs (serotonin syndrome)
- CYP3A4 inhibitors (increased fentanyl levels)
- Benzodiazepines (FDA black box — additive respiratory depression)
- Naloxone (reversal agent)
Clinical Pearls
- 100× more potent than morphine
- Preferred opioid in ICU due to minimal histamine release (vs. morphine) and less hemodynamic compromise
- Chest wall rigidity: use NMB or naloxone; prevent with slow administration
- Analgesia-First sedation: treat pain before adding sedative (fentanyl first, then propofol/midazolam)
- Reversal: naloxone 0.04–0.4 mg IV (titrate to respiratory effect, not full reversal to avoid pain crisis)
- Context-sensitive half-life increases significantly with prolonged infusion
Mnemonic
💡 Fentanyl: Fast (1–2 min IV), Fifty... no, 100× morphine potency
NBRC High-Yield
- 100× more potent than morphine
- Preferred ICU opioid — minimal histamine, less hemodynamic instability
- Chest wall rigidity with rapid high-dose boluses
- Reversal: naloxone
- Analgesia-first approach in ICU: treat pain before adding sedation
- SpO2 and respiratory rate monitoring mandatory