What is the oral morphine to oral hydromorphone conversion ratio for pain management?

Oral Morphine to Oral Hydromorphone Conversion Ratio

The conversion ratio from oral morphine to oral hydromorphone is 5:1, meaning 30 mg of oral morphine equals approximately 6 mg of oral hydromorphone. 1

Evidence-Based Conversion Ratio

The 5:1 conversion ratio is consistently supported across multiple high-quality sources:

• The NCCN guidelines establish that 60 mg of oral morphine daily equals 12 mg of oral hydromorphone daily, confirming the 5:1 ratio 1
• The FDA label for hydromorphone demonstrates that 5 mg and 10 mg of oral hydromorphone provided comparable pain relief to 30 mg and 60 mg of oral morphine respectively, directly validating the 5:1 conversion 2
• A systematic review of opioid conversion ratios found consistent data supporting a 5:1 ratio between oral morphine and oral hydromorphone 3

Clinical Application Algorithm

Step 1: Calculate Total Daily Morphine Dose

• Sum all morphine doses taken in 24 hours 1

Step 2: Apply the 5:1 Conversion Ratio

• Divide the total daily oral morphine dose by 5 to obtain the equianalgesic hydromorphone dose 1
• Example: 60 mg morphine daily ÷ 5 = 12 mg hydromorphone daily

Step 3: Reduce for Incomplete Cross-Tolerance

• Reduce the calculated hydromorphone dose by 25-50% to account for incomplete cross-tolerance and individual variability 1
• For well-controlled pain with stable patients: use 25% reduction 1
• For safer, more conservative conversion: use 50% reduction 1

Step 4: Divide into Scheduled Doses

• Distribute the total daily hydromorphone dose across appropriate dosing intervals 1
• Immediate-release hydromorphone: typically every 4 hours (6 doses daily)
• Extended-release hydromorphone: every 12-24 hours depending on formulation

Step 5: Prescribe Breakthrough Medication

• Provide immediate-release hydromorphone for breakthrough pain at 10-15% of the total daily dose 1

Important Clinical Considerations

Monitoring Requirements

• Close monitoring is mandatory during the first 48-72 hours after conversion for adequate pain control and adverse effects including sedation, respiratory depression, and nausea 1
• Reassess pain intensity within 24-48 hours of conversion 4

Special Populations

• In patients with renal impairment (eGFR <30 mL/min), hydromorphone should be used with caution at reduced doses and frequency, as it has less problematic metabolite accumulation compared to morphine 1

Dose-Dependent Considerations

• Research suggests that higher baseline morphine doses (≥240 mg/day morphine equivalent) may require slightly lower conversion ratios, though the 5:1 ratio with appropriate dose reduction remains the standard approach 5
• Studies using an 8:1 conversion ratio (morphine to extended-release hydromorphone) found that 43% of patients remained at their initial conversion dose, while 54% required dose increases, suggesting the 5:1 ratio with dose reduction is more appropriate 6

Mandatory Concurrent Management

Bowel Regimen

• Always prescribe a stimulant laxative (senna/docusate) prophylactically starting at 2 tablets every morning from day one of opioid therapy 1
• Increase laxative dose when escalating opioid doses 1
• Maintain adequate hydration and dietary fiber 1

Common Pitfalls to Avoid

• Do not use simple mathematical conversion without dose reduction - this approach fails to account for incomplete cross-tolerance and can lead to overdosing 4
• Do not apply conversion ratios in reverse - the bidirectional conversion is not symmetrical due to pharmacokinetic differences 1
• Avoid assuming all patients will respond identically - individual titration based on clinical response is essential after initial conversion 4