What is the clinical algorithm for converting an opioid‑tolerant patient receiving at least 60 mg oral morphine per day for ≥24 hours with stable pain to a transdermal fentanyl patch?

Clinical Algorithm for Converting Morphine to Transdermal Fentanyl Patch

For opioid-tolerant patients receiving ≥60 mg oral morphine daily with stable pain, calculate the 24-hour morphine requirement, use the conversion table to select the appropriate fentanyl patch strength (typically 25 mcg/hr for 60-134 mg/day oral morphine), continue short-acting opioids for breakthrough pain during the first 8-24 hours, and reassess after 2-3 days when steady state is achieved. 1, 2

Step 1: Verify Patient Eligibility

• Confirm opioid tolerance: Patient must be receiving ≥60 mg oral morphine equivalents per day for at least 24 hours 3
• Assess pain stability: Fentanyl patches are contraindicated for unstable pain requiring frequent dose adjustments 1, 2
• Rule out contraindications: Exclude opioid-naive patients, those with fever, and situations requiring rapid dose titration 1, 3

Step 2: Calculate Total 24-Hour Morphine Requirement

• For oral morphine: Add all doses taken in 24 hours (scheduled + PRN actually consumed) 2
• For IV/subcutaneous morphine: Multiply hourly rate by 24, or sum all bolus doses given in 24 hours 2
• Use actual consumption: Base calculation on what effectively controls pain, not just prescribed doses 4

Step 3: Select Initial Fentanyl Patch Strength Using Conversion Table

The FDA-approved and NCCN-endorsed conversion ratios are 1, 3:

Oral Morphine (mg/day)	IV/SubQ Morphine (mg/day)	Fentanyl Patch (mcg/hr)
60-134	20-44	25
135-224	45-74	50
225-314	75-104	75
315-404	105-134	100

• Conservative approach: The conversion is designed to underestimate requirements to prevent overdose 3
• Intermediate strengths: 37.5 mcg/hr and 62.5 mcg/hr patches are available for fine-tuning 3
• High-dose patients: For requirements >100 mcg/hr, multiple patches may be applied 3

Step 4: Manage the Transition Period (First 12-24 Hours)

• Timing of patch application: Apply the first patch and discontinue scheduled long-acting morphine 2, 3
• Continue breakthrough medication: Maintain immediate-release morphine (10 mg PO or 3-4 mg IV) every 1-2 hours as needed, representing 10-15% of the 24-hour opioid requirement 1, 2
• Therapeutic lag: Fentanyl takes 12-24 hours to reach therapeutic blood levels, so breakthrough opioids are essential during this period 1, 2
• Do NOT restrict rescue medication: Patients require unrestricted access to short-acting opioids for at least 72 hours 1

Step 5: Monitor and Titrate (Days 2-3)

• Steady-state timing: Fentanyl reaches steady state in 2-3 days (after the second patch application) 1, 2
• Track breakthrough use: Document the total amount of rescue medication consumed daily 1, 2
• Dose adjustment: If breakthrough medication requirements are high, increase the patch strength based on the average daily rescue dose consumed 1, 2
• Patch duration: Standard replacement is every 72 hours, but some patients require 48-hour changes if pain returns prematurely 1, 2

Critical Safety Precautions

• Heat exposure: Never apply heat sources (heating pads, electric blankets, fever) as this accelerates fentanyl absorption and can cause fatal overdose 1, 2
• Withdrawal risk: Three patients in one study experienced morphine withdrawal syndrome within the first 24 hours of conversion, emphasizing the need for adequate breakthrough coverage 5
• Respiratory monitoring: Monitor closely for respiratory depression, especially in the first 24-72 hours 4
• Skin reactions: Cutaneous reactions to patches are typically mild and transient 5

Common Pitfalls to Avoid

• Do NOT use the conversion table in reverse: These tables cannot be used to convert FROM fentanyl TO other opioids, as this will overestimate the new opioid dose and risk fatal overdose 3
• Do NOT abruptly discontinue breakthrough medication: Continue short-acting opioids even after the patch is in place 1
• Do NOT initiate in opioid-naive patients: This is an absolute contraindication 1, 3
• Do NOT adjust patches more frequently than every 3 days: Allow time to reach steady state before titrating 1, 2

Alternative Conversion Ratio

• One multicenter study found that a 70:1 ratio (oral morphine mg : fentanyl mcg/hr) may be more accurate than the standard 100:1 ratio, though the FDA-approved 100:1 ratio remains safer for initial conversion 5
• The conservative FDA approach (100:1) minimizes overdose risk and allows for upward titration based on breakthrough needs 3