What is the conversion ratio from intravenous (IV) fentanyl to IV Dilaudid (hydromorphone) for a patient with potential impaired renal or hepatic function?

IV Fentanyl to IV Hydromorphone Conversion

For converting IV fentanyl to IV hydromorphone (Dilaudid), use a two-step conversion: first convert IV fentanyl to IV morphine using a 100:1 ratio (100 mcg fentanyl = 1 mg morphine), then convert IV morphine to IV hydromorphone using a 5:1 ratio (5 mg morphine = 1 mg hydromorphone), resulting in an overall ratio of approximately 500:1 (500 mcg IV fentanyl = 1 mg IV hydromorphone). 1

Step-by-Step Conversion Algorithm

Step 1: Calculate Total Daily IV Fentanyl Dose

• Multiply the hourly fentanyl infusion rate by 24 hours to determine total daily fentanyl dose in micrograms 1

Step 2: Convert IV Fentanyl to IV Morphine Equivalent

• Multiply the total daily fentanyl dose (in mcg) by 0.01 to convert to IV morphine equivalents using the established 100:1 ratio 1
• Example: 2400 mcg/day IV fentanyl = 24 mg/day IV morphine

Step 3: Convert IV Morphine to IV Hydromorphone

• Divide the IV morphine dose by 5 to obtain the equivalent IV hydromorphone dose, using the standard 5:1 conversion ratio 1, 2, 3
• Example: 24 mg/day IV morphine = 4.8 mg/day IV hydromorphone

Step 4: Apply Dose Reduction for Incomplete Cross-Tolerance

• Reduce the calculated hydromorphone dose by 25-50% to account for incomplete cross-tolerance between opioids 1, 4, 2
• If pain was well-controlled on fentanyl, use the 50% reduction (more conservative) 4, 2
• If pain was poorly controlled, use only 25% reduction or even 100% of calculated dose 1, 4
• Example: 4.8 mg/day reduced by 50% = 2.4 mg/day IV hydromorphone

Step 5: Divide Into Appropriate Dosing Schedule

• Divide the total daily hydromorphone dose by 6 for every-4-hour dosing, or provide as continuous infusion 1
• Example: 2.4 mg/day ÷ 24 hours = 0.1 mg/hour continuous infusion

Critical Considerations for Renal or Hepatic Impairment

Renal Dysfunction

• Hydromorphone is preferred over morphine in renal impairment because its metabolites are less neurotoxic, though caution is still warranted in severe renal dysfunction 1, 2
• Morphine should be avoided entirely if creatinine clearance is below 30 mL/min due to accumulation of morphine-6-glucuronide, which causes neurotoxicity 1, 4
• Hydromorphone metabolites may still accumulate and cause myoclonus, hyperalgesia, and seizures in severe renal impairment, though less problematic than morphine 1
• In severe renal impairment (CrCl <30 mL/min), start with 50% of the calculated hydromorphone dose and monitor closely for neurotoxicity 4, 2

Hepatic Dysfunction

• Both fentanyl and hydromorphone undergo hepatic metabolism, so dose adjustments may be necessary in hepatic impairment 1
• Start with the lower end of the dose reduction range (50% reduction) in hepatic dysfunction 4

Monitoring and Titration Protocol

Initial 24-48 Hours

• Monitor pain scores and sedation levels every 4-6 hours during the first 24-48 hours after conversion 4
• Assess for signs of opioid toxicity: excessive sedation, respiratory depression, myoclonus, confusion 1, 4
• Watch for signs of inadequate pain control: pain scores >4/10, frequent breakthrough medication use 4, 2

Breakthrough Pain Management

• Prescribe immediate-release hydromorphone for breakthrough pain at 10-15% of the total daily dose 4, 2
• If patient requires more than 3-4 breakthrough doses per day, increase the scheduled baseline dose by 25-50% 4, 2

Dose Adjustments

• If pain remains >4/10 on average, increase total daily dose by 25-50% 2
• Titrate liberally during the first 24 hours if previous pain control was inadequate 1

Common Pitfalls and How to Avoid Them

Pitfall 1: Using Transdermal Fentanyl Conversion Ratios

• Never use the 1:1 transdermal-to-IV fentanyl conversion ratio when converting from IV fentanyl to other IV opioids 4, 5, 6
• The transdermal conversion applies only when switching between transdermal and IV fentanyl formulations, not when converting to different opioids 1, 4

Pitfall 2: Forgetting Incomplete Cross-Tolerance

• Always reduce the calculated equianalgesic dose by 25-50% unless pain was poorly controlled 1, 4, 2
• Failure to account for incomplete cross-tolerance can lead to opioid toxicity 4, 7

Pitfall 3: Using Morphine in Renal Failure

• Avoid morphine entirely in patients with CrCl <30 mL/min; hydromorphone is the safer alternative 1, 4
• If morphine must be used despite renal impairment, start with 25-50% of calculated dose 4

Pitfall 4: Inadequate Breakthrough Coverage

• Patients often need more breakthrough medication during the first 24 hours of conversion 4, 6
• Ensure adequate PRN hydromorphone is available (10-15% of total daily dose per breakthrough dose) 4, 2

Pitfall 5: Fixed Ratio Application Without Clinical Judgment

• Conversion ratios are approximate guides; individual patient factors (age, comorbidities, opioid tolerance) must be considered 4, 2, 7
• Higher baseline fentanyl doses may require lower conversion ratios due to incomplete cross-tolerance 3, 7

Practical Example

For a patient on 100 mcg/hour IV fentanyl (2400 mcg/day):

1. Convert to IV morphine: 2400 mcg ÷ 100 = 24 mg/day IV morphine 1
2. Convert to IV hydromorphone: 24 mg ÷ 5 = 4.8 mg/day IV hydromorphone 1, 2
3. Reduce by 50% for cross-tolerance: 4.8 mg × 0.5 = 2.4 mg/day 4, 2
4. Final dose: 0.1 mg/hour IV hydromorphone continuous infusion 1
5. Breakthrough: 0.4 mg IV hydromorphone every 2-4 hours as needed 4, 2