What is the opioid conversion scale for an adult patient with no significant comorbidities or substance abuse history?

Opioid Conversion Scale

Use the National Comprehensive Cancer Network equianalgesic conversion ratios as your foundation, with a mandatory 25-50% dose reduction when switching opioids to account for incomplete cross-tolerance. 1

Core Equianalgesic Conversion Ratios

Standard Opioid Conversions (Oral to Oral)

• Morphine 30 mg oral = Oxycodone 20 mg oral (ratio 1.5:1) 1, 2
• Morphine 30 mg oral = Hydromorphone 7.5 mg oral (ratio 4:1) 1
• Morphine 30 mg oral = Oxymorphone 10 mg oral (ratio 3:1) 1
• Morphine 30 mg oral = Codeine 200 mg oral 1
• Oxycodone 20 mg oral = Hydromorphone 4 mg oral (ratio 1:4) 2

Parenteral (IV/SubQ) Conversions

• Morphine 10 mg IV = Hydromorphone 1.5 mg IV (ratio approximately 7:1) 1
• Morphine 10 mg IV = Fentanyl 0.1 mg IV 1
• Oral to IV morphine ratio: 3:1 (30 mg oral morphine = 10 mg IV morphine) 1

Transdermal Fentanyl Conversions

Use this table for converting to transdermal fentanyl patches: 1

• 25 mcg/h patch = 60 mg/day oral morphine = 30 mg/day oral oxycodone = 7.5 mg/day oral hydromorphone 1
• 50 mcg/h patch = 120 mg/day oral morphine = 60 mg/day oral oxycodone = 15 mg/day oral hydromorphone 1
• 75 mcg/h patch = 180 mg/day oral morphine = 90 mg/day oral oxycodone = 22.5 mg/day oral hydromorphone 1
• 100 mcg/h patch = 240 mg/day oral morphine = 120 mg/day oral oxycodone = 30 mg/day oral hydromorphone 1

Methadone Conversions (Dose-Dependent Ratios)

Methadone conversion ratios vary dramatically based on the baseline morphine dose: 1

• Oral morphine 30-90 mg/day: Use 4:1 ratio (morphine:methadone) 1
• Oral morphine 91-300 mg/day: Use 8:1 ratio 1
• Oral morphine >300 mg/day: Use 12:1 ratio or higher; cross-titration recommended 1

Step-by-Step Conversion Algorithm

Step 1: Calculate Total 24-Hour Current Opioid Dose

• Sum all scheduled and breakthrough doses taken in 24 hours 1
• Convert combination products (e.g., oxycodone/acetaminophen) to opioid-only equivalent 1

Step 2: Convert to Equianalgesic Dose of New Opioid

• Use the conversion ratios above to calculate the theoretical equivalent dose 1
• For opioids not listed, first convert to oral morphine equivalents, then to target opioid 1

Step 3: Apply Dose Reduction for Cross-Tolerance

Critical safety step: 1

• If pain was well-controlled: Reduce calculated dose by 25-50% 1
• If pain was poorly controlled: May use 100% of calculated dose or increase by 25% 1
• Conservative approach recommended: Start with 50% reduction for safety 3, 4

Step 4: Divide Into Appropriate Dosing Schedule

• Immediate-release formulations: Divide by 4-6 doses per day 1, 3
• Extended-release formulations: Divide by 2 doses per day (every 12 hours) 1
• Transdermal patches: Apply calculated patch strength every 72 hours (some patients need every 48 hours) 1

Worked Clinical Examples

Example 1: IV Morphine to IV Hydromorphone

Patient on morphine 8 mg/hour IV (192 mg/day): 1

1. Calculate 24-hour dose: 8 mg/h × 24h = 192 mg/day IV morphine 1
2. Convert using 10 mg IV morphine = 1.5 mg IV hydromorphone: 192 ÷ 10 × 1.5 = 28.8 mg/day IV hydromorphone 1
3. Reduce by 50% for cross-tolerance: 28.8 × 0.5 = 14.4 mg/day IV hydromorphone (0.6 mg/hour) 1

Example 2: Oral Oxycodone to Transdermal Fentanyl

Patient on oxycodone 30 mg every 12 hours (60 mg/day): 1

1. Calculate 24-hour dose: 30 mg × 2 = 60 mg/day oral oxycodone 1
2. Use conversion table directly: 60 mg/day oral oxycodone = 50 mcg/h fentanyl patch 1
3. Provide immediate-release opioid for breakthrough during first 24 hours 1

Example 3: Oral Morphine to Oral Methadone

Patient on morphine 30 mg every 4 hours (180 mg/day): 1

1. Calculate 24-hour dose: 30 mg × 6 = 180 mg/day oral morphine 1
2. Use 8:1 ratio (for 91-300 mg/day range): 180 ÷ 8 = 22.5 mg/day methadone 1
3. Reduce by 25%: 22.5 × 0.75 = 16.9 mg/day ≈ 15 mg/day methadone 1
4. Divide into 3 doses: 5 mg every 8 hours 1

Critical Safety Considerations

Avoid These Common Pitfalls

• Never use methadone conversion ratios in reverse (methadone to other opioids requires different approach due to long half-life) 1
• Avoid codeine and morphine in renal failure (accumulation of toxic metabolites) 1
• Do not use mixed agonist-antagonists with pure agonists (can precipitate withdrawal) 1
• Online calculators show dangerous variability—perform manual calculations 5

Special Monitoring Requirements

• Monitor for respiratory depression within first 24-72 hours after any opioid conversion 3
• Methadone requires baseline and follow-up ECG for doses >100 mg/day or in cardiac disease (QTc prolongation risk) 1
• Transdermal fentanyl requires 2-3 days to reach steady state—continue breakthrough medication 1
• Reassess within 24 hours after dose adjustments 6

Breakthrough Pain Management

• Provide immediate-release opioid at 10-20% of total daily dose for breakthrough pain 6
• If requiring >3-4 breakthrough doses daily: Increase scheduled dose by 25-50% rather than shortening interval 6

Mandatory Supportive Care

• Institute prophylactic bowel regimen with stimulant laxatives (constipation is universal with opioids) 1, 6
• Titrate laxatives when increasing opioid doses 1

When Converting to Extended-Release Formulations

• Relative bioavailability between immediate and extended-release is variable—close observation required 3
• For chronic pain, use around-the-clock dosing to prevent pain recurrence rather than treating after onset 3
• If pain returns before next scheduled dose: Increase total daily dose by 25-50%, do not shorten dosing interval 6

1, 7, 6, 3, 2, 5, 4