Fentanyl Dosing Guidelines
The recommended dose of fentanyl varies by route of administration and patient population, with intraoperative dosing typically 1-2 mcg/kg for adults and 0.5-1.0 mcg/kg for breakthrough pain in the post-anesthesia care unit. 1
Intravenous Fentanyl Dosing
Adult Dosing
- Intraoperative use: 1-2 mcg/kg 1
- Breakthrough pain in PACU: 0.5-1.0 mcg/kg, titrated to effect 1
- IV to transdermal conversion: Use 1:1 ratio (mcg/hr IV = mcg/hr transdermal) 1, 2
- IV morphine to IV fentanyl conversion: Use 100:1 ratio (morphine:fentanyl) 2
Pediatric Dosing
- Intraoperative use: 1-2 mcg/kg 1
- Breakthrough pain in PACU: 0.5-1.0 mcg/kg, titrated to effect 1
- Intrathecal administration for labor analgesia: Up to 15 mcg fentanyl (often combined with local anesthetic) 1
Transdermal Fentanyl Dosing
Conversion from Other Opioids
Use this table for conversion to transdermal fentanyl:
| Transdermal Fentanyl | Oral Morphine | Oral Oxycodone | Oral Hydromorphone |
|---|---|---|---|
| 25 mcg/hr | 60 mg/day | 30 mg/day | 7.5 mg/day |
| 50 mcg/hr | 120 mg/day | 60 mg/day | 15 mg/day |
| 75 mcg/hr | 180 mg/day | 90 mg/day | 22.5 mg/day |
| 100 mcg/hr | 240 mg/day | 120 mg/day | 30 mg/day |
Administration Guidelines
- Apply to clean, dry, non-irritated skin on upper torso 2
- Each patch typically worn for 72 hours (some patients require replacement every 48 hours) 1, 2
- Provide breakthrough medication for first 24 hours while patch reaches steady state 2
- Adjust patch dosage after 2-3 days based on breakthrough medication requirements 1, 2
Important Considerations and Precautions
Patient Selection
- Transdermal fentanyl is only for opioid-tolerant patients with stable pain patterns 2, 3
- Not appropriate for acute pain, postoperative pain, or unstable pain requiring frequent dose changes 1, 2
- Patients should be on equivalent of at least 60 mg oral morphine per day before starting transdermal fentanyl 2, 3
Safety Precautions
- Monitor for respiratory depression, especially during initiation and dose increases 2
- Avoid heat application (including fever, heat lamps, electric blankets) as it accelerates absorption 1, 2
- Ensure proper patch disposal and removal of old patches before applying new ones 2
- Have naloxone readily available for reversal if needed 2
Pharmacokinetic Considerations
- Fentanyl is 50-100 times more potent than morphine 2
- IV administration: onset 1-2 minutes, duration 30-60 minutes with single doses 2
- Transdermal administration: 17-48 hour delay before maximum plasma concentration 4
- Intranasal/transmucosal routes provide faster delivery (Tmax ~12-20 minutes) 5
Common Pitfalls to Avoid
Inappropriate patient selection: Using transdermal fentanyl in opioid-naïve patients or those with unstable pain can lead to respiratory depression 1, 2
Incorrect conversion calculations: Using transdermal-to-oral conversion tables backward can result in fatal overdose 3
Failure to provide breakthrough medication: During initial patch application or for breakthrough pain 1, 2
Applying heat to patch site: Can cause dangerous increases in absorption rates 1, 2
Combining with other CNS depressants: Particularly midazolam, which increases respiratory depression risk 2