How to convert a patient from methadone (opioid agonist) 65mg to fentanyl (synthetic opioid) patch?

Converting Methadone 65mg to Fentanyl Patch

Convert methadone 65mg daily to oral morphine equivalent first (approximately 130-195mg/day using a 2:1 to 3:1 ratio), then use this morphine equivalent to select a 50 mcg/hour fentanyl patch, while providing immediate-release opioid for breakthrough pain during the first 24 hours. 1, 2, 3

Step-by-Step Conversion Algorithm

Step 1: Convert Methadone to Oral Morphine Equivalent

• The critical challenge is that methadone-to-morphine conversion ratios are NOT bidirectional - the guidelines explicitly warn against using morphine-to-methadone tables in reverse 1
• For methadone 65mg/day, use a conservative 1:1 ratio on day one of conversion (while methadone is still present in the system), which equals approximately 65mg morphine equivalent 1
• However, as methadone clears over several days due to its long half-life, the true morphine equivalent will be higher - likely 130-195mg/day based on typical conversion ratios of 2:1 to 3:1 for this methadone dose range 1
• Use the higher estimate (130-195mg morphine equivalent) to select your fentanyl patch dose to avoid undertreatment 1, 2

Step 2: Select Fentanyl Patch Strength

• Based on 135-224mg/day oral morphine equivalent, initiate a 50 mcg/hour fentanyl patch 2, 3
• The FDA conversion table confirms that 135-224mg/day oral morphine converts to a 50 mcg/hour patch 3
• Apply the patch and remove after 72 hours, replacing with a new patch 2, 3

Step 3: Timing of Methadone Discontinuation

• Stop methadone and apply the fentanyl patch simultaneously - do not wait 12-18 hours as you would when converting in the opposite direction 4, 5
• Research demonstrates that starting the new opioid immediately after stopping methadone prevents therapeutic gaps, as methadone levels decline slowly over days 4, 5
• Fentanyl levels will take 12-24 hours to reach therapeutic range, during which residual methadone provides coverage 2, 4, 6

Step 4: Breakthrough Medication

• Prescribe immediate-release morphine 10-20mg every 2-4 hours as needed for breakthrough pain (approximately 10-20% of total daily morphine equivalent) 2
• Breakthrough medication is essential during the first 24 hours as fentanyl levels continue rising to steady state 2, 7
• Monitor total breakthrough medication use over 48-72 hours to guide dose titration 2

Critical Safety Considerations

Opioid Tolerance Requirement

• Only use fentanyl patches in opioid-tolerant patients - methadone 65mg/day confirms tolerance 2, 7, 3
• This dose of methadone indicates significant tolerance, making fentanyl patch appropriate 3

Heat Exposure Warning

• Never apply heat sources (heating pads, electric blankets, heat lamps) to patch sites as this accelerates absorption and can cause fatal overdose 2, 7, 3

Monitoring During Conversion

• Assess pain control and sedation at 24 hours, 48 hours, and 72 hours after patch application 2
• Fentanyl levels continue rising for 12-24 hours after initial application 2, 7

Dose Titration After Initial Conversion

When to Adjust

• Wait at least 72 hours (one full patch cycle) before increasing the fentanyl dose 2, 3
• Calculate average daily breakthrough medication requirements over this period 2

How to Adjust

• If patient required significant breakthrough medication (>3-4 doses daily), increase patch strength by 25 mcg/hour 2
• Consider using 62.5 mcg/hour as an intermediate strength between 50 and 75 mcg/hour patches 3

Common Pitfalls to Avoid

Bidirectional Conversion Error

• The most critical error is using morphine-to-methadone conversion tables in reverse - this will overestimate the morphine equivalent and potentially cause overdose 1
• The conservative approach is to estimate lower initially (using 1:1 ratio) but have generous breakthrough medication available 1

Premature Dose Escalation

• Do not increase the fentanyl patch dose before 72 hours, as steady-state levels are not achieved until after the first patch cycle 2, 3

Inadequate Breakthrough Coverage

• Failing to provide adequate breakthrough medication during the first 24-48 hours is a common cause of conversion failure 2