Fentanyl Dosing Guidelines
The recommended dose of fentanyl varies by administration route, with intraoperative dosing typically 1-2 mcg/kg, breakthrough pain management at 0.5-1 mcg/kg IV, and transdermal dosing starting at 25 mcg/hour for opioid-tolerant patients with stable pain patterns. 1, 2
Intravenous Fentanyl Dosing
Intraoperative Use
- Children: 1-2 mcg/kg 1
- Adults: 1-2 mcg/kg titrated to effect
Post-Anesthesia Care Unit (PACU) for Breakthrough Pain
- Children: 0.5-1.0 mcg/kg, titrated to effect 1
- Adults: Similar dosing applies, with careful titration
Continuous Infusion
- When converting from IV morphine to IV fentanyl, use a 100:1 ratio (morphine:fentanyl) 3
Transdermal Fentanyl Dosing
Patient Selection
- Only for opioid-tolerant patients with stable pain patterns
- Not appropriate for acute pain, postoperative pain, or unstable pain requiring frequent dose adjustments 3, 2
Initial Dosing
- Use conversion tables to determine appropriate starting dose:
| 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 |
Conversion from IV Fentanyl
- Use a 1:1 ratio when converting from continuous IV fentanyl to transdermal fentanyl (μg/hr IV = μg/hr transdermal) 3
Administration
- Apply to clean, dry, non-irritated skin on upper torso
- Each patch is worn for 72 hours (some patients may require replacement every 48 hours)
- For doses exceeding 100 mcg/hr, multiple patches may be used 2
Intrathecal Fentanyl Dosing
Labor Analgesia
- Initial bolus: Up to 15 mcg fentanyl (often combined with local anesthetic) 1
- For maintenance: Typically administered with local anesthetic in intermittent boluses or continuous infusion
Oral Transmucosal Fentanyl
- Doses must be individually titrated
- Starting dose typically 200 mcg, regardless of around-the-clock opioid dose 4
- Titrate upward until effective dose is found
Important Safety Considerations
Respiratory Depression: Monitor respiratory rate and oxygen saturation, especially during initiation and dose increases
Heat Application: Avoid heat sources (fever, heating pads, electric blankets) with transdermal fentanyl as they accelerate absorption 3
Pediatric Dosing: Weight-based dosing is essential; children may require different dosing than adults 1, 3
Drug Interactions: Increased risk of respiratory depression when combined with other CNS depressants, particularly benzodiazepines 3
Hepatic Impairment: Reduce doses in patients with hepatic dysfunction due to altered metabolism 3
Common Pitfalls to Avoid
- Overestimating initial dose when converting from other opioids to fentanyl (especially transdermal)
- Failing to provide breakthrough medication during the first 24 hours of transdermal fentanyl application
- Cutting or altering transdermal patches, which can lead to unpredictable drug delivery
- Using transdermal fentanyl for acute or unstable pain
- Forgetting to remove old patches when applying new ones
Fentanyl is approximately 50-100 times more potent than morphine, with rapid onset of action (1-2 minutes IV) and relatively short duration (30-60 minutes with single IV doses), requiring careful dosing and monitoring to ensure both efficacy and safety 3.