What is the equivalent dose of oxycodone (OxyContin) for a patient taking 10mg of methadone (Dolophine) twice daily (BID)?

Converting Methadone 10mg BID to Oxycodone

Start with oxycodone 20mg daily (approximately 10mg every 12 hours), using a conservative 1:1 conversion ratio on day one, then titrate upward over the following days as residual methadone clears from the system. 1

Conversion Algorithm

Step 1: Calculate Total Daily Methadone Dose

• Current regimen: 10mg BID = 20mg methadone daily 1

Step 2: Apply Conservative Day-One Conversion

• The NCCN explicitly warns that standard conversion ratios should NOT be used when converting FROM methadone to other opioids 1
• Use a conservative 1:1 ratio (oral methadone to oral morphine) on the first day of conversion 1
• 20mg methadone = approximately 20mg morphine equivalent on day one 1

Step 3: Convert Morphine Equivalent to Oxycodone

• Using standard equianalgesic ratios: morphine to oxycodone is approximately 1.5:1 2
• 20mg morphine ÷ 1.5 = approximately 13mg oxycodone daily
• Round down to 10-12mg oxycodone daily initially (5-6mg every 12 hours) 2

Step 4: Account for Incomplete Cross-Tolerance

• Reduce the calculated dose by an additional 25-50% for safety 1, 2
• Final starting dose: approximately 5-10mg oxycodone every 12 hours (10-20mg daily total) 2

Critical Safety Considerations

Methadone's Unique Pharmacokinetics

• Methadone has a very long elimination half-life (mean 22 hours, range 5-130 hours), taking several days to clear completely 3, 4
• Residual methadone will continue providing analgesic effect for 2-3 days after discontinuation 1
• The oxycodone requirement will increase progressively over the first 3-5 days as methadone clears 1

Titration Strategy

• Provide immediate-release oxycodone 2-3mg (10-20% of 24-hour dose) every 4-6 hours as needed for breakthrough pain 2
• Reassess daily and increase the scheduled oxycodone dose by 25-50% every 1-2 days based on breakthrough medication requirements 1, 2
• Most patients will require dose adjustments for 3-5 days until methadone is fully cleared 1

Common Pitfalls to Avoid

Do Not Use Standard Morphine-to-Methadone Ratios in Reverse

• The conversion ratios for morphine-to-methadone (ranging from 4:1 to 12:1 depending on morphine dose) are NOT bidirectional 1
• Using these ratios in reverse would result in dangerous overdosing due to residual methadone 1

Monitor for Oversedation Early

• The greatest risk of oversedation occurs in the first 24-48 hours when both medications overlap 2, 5
• Have naloxone immediately available 6

Expect Underdosing Initially

• The conservative approach will likely result in inadequate analgesia initially, but this is safer than overdosing 1
• Be prepared to titrate upward aggressively based on pain control and breakthrough medication use 2

Practical Dosing Recommendation

Day 1-2: Oxycodone 5mg every 12 hours (10mg daily) + oxycodone IR 2-3mg every 4-6 hours PRN 2

Day 3-4: Increase to oxycodone 10mg every 12 hours (20mg daily) if using ≥3 breakthrough doses daily 2

Day 5-7: Continue titrating upward by 25-50% every 1-2 days until pain is controlled, typically reaching 30-40mg oxycodone daily (equivalent to the original methadone dose using higher conversion ratios) 1, 2