Fentanyl Dosing Guidelines
The recommended dose of fentanyl varies by administration route, with intraoperative doses of 1-2 mcg/kg, breakthrough pain doses of 0.5-1.0 mcg/kg titrated to effect, and transdermal doses starting at 25 mcg/hour for opioid-tolerant patients with stable pain patterns. 1, 2
Intravenous Fentanyl Dosing
Intraoperative Use
- Fentanyl: 1-2 mcg/kg 1
- For pediatric patients, doses are weight-based and depend on the procedure type
Breakthrough Pain Management
- PACU/acute setting: 0.5-1.0 mcg/kg, titrated to effect 1
- Onset of action: 1-2 minutes
- Duration of effect: 30-60 minutes with single IV doses 3
- Note that fentanyl is 50-100 times more potent than morphine 3
Continuous Infusion
- When converting from IV morphine to IV fentanyl, use a conversion ratio of 100:1 (morphine:fentanyl) 3
- When converting from continuous parenteral infusion fentanyl to transdermal fentanyl, use a 1:1 ratio (mcg of parenteral fentanyl equals mcg/h of transdermal fentanyl) 1
Transdermal Fentanyl Dosing
Patient Selection
- Only for opioid-tolerant patients with stable pain patterns 3, 2
- Not recommended for acute pain, postoperative pain, or unstable pain requiring frequent dose changes 3, 2
- Indicated for patients taking at least:
- 60 mg oral morphine per day
- 30 mg oral oxycodone per day
- 8 mg oral hydromorphone per day 3
Dosing Conversion Table
| Transdermal Fentanyl | Oral Morphine | Oral Oxycodone | Oral Hydromorphone |
|---|---|---|---|
| 25 mcg/hr | 60-134 mg/day | 30-67 mg/day | 7.5-17 mg/day |
| 50 mcg/hr | 135-224 mg/day | 67.5-112 mg/day | 17.1-28 mg/day |
| 75 mcg/hr | 225-314 mg/day | 112.5-157 mg/day | 28.1-39 mg/day |
| 100 mcg/hr | 315-404 mg/day | 157.5-202 mg/day | 39.1-51 mg/day |
| [1,2] |
Administration
- Each patch is worn for 72 hours (some patients require replacement every 48 hours) 1, 3
- Apply to clean, dry, non-irritated, flat skin on the upper torso 3
- Rotate application sites 3
- Provide breakthrough medication for the first 24 hours while the patch reaches steady state 1, 3
- Adjust patch dosage after 2-3 days based on breakthrough medication requirements 1, 3
Intrathecal Fentanyl Dosing
Labor Analgesia
- Initial bolus: up to 15 mcg fentanyl (often combined with local anesthetic) 1
- For initiation of labor analgesia via an intrathecal catheter: 2.5 mg bupivacaine with up to 15 mcg fentanyl 1
Oral Transmucosal Fentanyl
- Starting dose typically 200 mcg or 400 mcg 4
- Titrate to effective dose for breakthrough pain
- Effective dose not predicted by around-the-clock opioid dose 4
Important Safety Considerations
- Monitor for respiratory depression, especially during initiation and dose increases 3
- Avoid heat application with transdermal fentanyl as it accelerates absorption 1, 3
- Have naloxone readily available for reversal if needed 3
- Use caution when combining with other sedatives, particularly midazolam, as this significantly increases the risk of respiratory depression 3
- Reduce midazolam dose by 25-50% when used with opioids due to synergistic effects 3
- Exercise caution in patients with hepatic impairment; reduce doses due to fentanyl's metabolism in the liver 3
Common Pitfalls to Avoid
- Using transdermal fentanyl for acute or unstable pain
- Failing to provide breakthrough medication during initial transdermal application
- Applying heat to transdermal patches
- Overestimating initial doses when converting from other opioids
- Cutting or altering patches
- Forgetting to remove old patches when applying new ones
- Using conversion tables meant for converting TO fentanyl when converting FROM fentanyl (will result in overdose) 1, 2
Fentanyl's high potency requires careful dosing and monitoring to balance effective pain control with the risk of serious adverse effects, particularly respiratory depression.