How do you switch an adult patient with chronic pain from oral (per oral) hydromorphone to transdermal fentanyl?

Converting from Oral Hydromorphone to Transdermal Fentanyl

Convert oral hydromorphone to transdermal fentanyl by first calculating the 24-hour oral morphine equivalent dose, then using established conversion tables to determine the appropriate fentanyl patch strength, while providing breakthrough medication during the 12-24 hour transition period. 1, 2

Step-by-Step Conversion Algorithm

Step 1: Calculate Total Daily Oral Hydromorphone Dose

• Add up all oral hydromorphone doses taken in a 24-hour period 3
• Document whether pain was well-controlled or poorly controlled on the current regimen 1

Step 2: Convert to Oral Morphine Equivalent

• Use the equianalgesic ratio: 1 mg oral hydromorphone = approximately 4 mg oral morphine 1
• For example: 12 mg/day oral hydromorphone = 48 mg/day oral morphine 1
• Note: The FDA label provides conversion ratios for IV hydromorphone (1.5 mg IV = 10 mg IV morphine), but oral hydromorphone requires different calculations 1, 2

Step 3: Determine Fentanyl Patch Dose Using Conversion Table

Use the FDA-approved conversion table based on 24-hour oral morphine equivalents 2:

Oral Morphine (mg/day)	Fentanyl Patch (mcg/hour)
60-134	25
135-224	50
225-314	75
315-404	100

• Intermediate strengths (37.5 mcg/hr and 62.5 mcg/hr) are available for fine-tuning 2

Step 4: Adjust for Cross-Tolerance and Pain Control Status

• If pain was well-controlled: Consider reducing the calculated fentanyl dose by 25-50% to account for incomplete cross-tolerance 1
• If pain was poorly controlled: Use 100% of the calculated equianalgesic dose or consider increasing by 25% 1
• This conservative approach minimizes overdose risk while maintaining adequate analgesia 2

Step 5: Manage the Transition Period (Critical)

• Apply the fentanyl patch and continue oral hydromorphone for the first 12 hours 3, 4
• Fentanyl patches take 12-24 hours to reach therapeutic blood levels 3, 5
• After 12 hours, discontinue the scheduled oral hydromorphone 4

Step 6: Prescribe Breakthrough Medication

• Provide short-acting opioid for breakthrough pain, typically 10-15% of the total daily opioid dose 3
• Breakthrough medication is essential during the first 8-24 hours as fentanyl levels reach steady state 3, 1
• Continue breakthrough medication availability even after stabilization 1

Dose Titration and Monitoring

Initial Adjustment Period

• Fentanyl reaches steady state after 2-3 days 3, 1
• Adjust the patch dose based on average breakthrough medication requirements after this period 3, 1
• Do not adjust more frequently than every 3 days after initial dose, then every 6 days thereafter 2

Patch Application Schedule

• Change patches every 72 hours as standard 3, 2
• Some patients may require replacement every 48 hours 3, 1

Critical Safety Considerations and Pitfalls

Contraindications and Precautions

• Only use in opioid-tolerant patients - transdermal fentanyl is contraindicated in opioid-naive patients 1, 2
• Do NOT use for unstable pain requiring frequent dose changes 3, 1
• Pain should be relatively well-controlled on short-acting opioids before initiating the patch 1

Heat Exposure Warning

• Avoid all heat sources (fever, heating pads, electric blankets, heat lamps) as heat accelerates fentanyl absorption and can cause overdose 3, 1

Respiratory Depression Risk

• Highest risk occurs during the first 24-72 hours of transition 1
• The prolonged elimination half-life (16-22 hours after patch removal) means adverse effects do not resolve immediately after patch removal 5
• If respiratory depression occurs, treat with naloxone and monitor for at least 24 hours; sequential doses or continuous infusion may be necessary due to naloxone's short half-life 5

Patient Counseling

• Instruct patients to refrain from driving or operating machinery immediately after patch initiation or dose increases until absence of cognitive/physical impairment is documented 5
• Individual patient variability necessitates close monitoring during conversion 1

Important Clinical Context

The conversion tables are intentionally conservative and unidirectional - they are designed only for converting TO fentanyl, not FROM fentanyl to other opioids, as reverse calculations would overestimate doses and risk fatal overdose 2. The substantial inter-patient variability in opioid potency makes it preferable to underestimate initial fentanyl requirements and provide rescue medication rather than risk overdosing 2.