What are the guidelines for converting a patient to hydromorphone (opioid analgesic)?

Hydromorphone Conversion Guidelines

When converting to hydromorphone, use a 5:1 ratio for IV morphine to IV hydromorphone (10 mg IV morphine = 2 mg IV hydromorphone), and reduce the calculated dose by 25-50% to account for incomplete cross-tolerance if pain was previously well-controlled. 1

Step-by-Step Conversion Protocol

1. Calculate Current 24-Hour Opioid Requirement

• Determine the total amount of current opioid taken in a 24-hour period that effectively controls pain 1
• For patients on multiple opioids, convert all to morphine equivalents first before converting to hydromorphone 1

2. Apply Conversion Ratios

IV to IV Conversions:

• Use a 5:1 ratio: 10 mg IV morphine = 2 mg IV hydromorphone 1, 2
• This ratio is approximately 5-7 times more potent than morphine 2

IV to Oral Hydromorphone:

• Use a 2.5:1 ratio: 1 mg IV hydromorphone = 2.5 mg oral hydromorphone 3
• The FDA label recommends starting with one-fourth to one-half the usual dose in hepatic or renal impairment 4

Oral Morphine to Oral Hydromorphone:

• Use a 5:1 ratio for conversion 1, 5
• Research supports ratios ranging from 1:5 to 1:8 depending on dose level 6

3. Reduce for Incomplete Cross-Tolerance

Critical Safety Step:

• If pain was effectively controlled on the previous opioid, reduce the calculated hydromorphone dose by 25-50% 1, 2
• If pain was poorly controlled, you may begin with 100% of the equianalgesic dose or increase by 25% 1
• This reduction accounts for incomplete cross-tolerance between different opioids and prevents overdosing 1

4. Dosing Schedule

For Immediate-Release Oral Hydromorphone:

• Initiate at 2-4 mg orally every 4-6 hours for opioid-naïve patients 4
• For chronic pain, administer scheduled doses around-the-clock rather than as-needed 4
• Provide breakthrough doses of 10-20% of the total 24-hour dose for transient pain exacerbations 2

For IV Hydromorphone:

• Administer bolus doses every 15 minutes as required for adequate pain control in acute settings 2
• For continuous infusions with breakthrough pain, give a bolus equal to or double the hourly infusion rate 2
• If two bolus doses are required within one hour, consider doubling the infusion rate 2

Practical Conversion Example

Case: Converting IV Morphine to IV Hydromorphone 1

A patient receiving 8 mg/h IV morphine (192 mg/day total):

1. Calculate equianalgesic dose: 192 mg IV morphine ÷ 5 = 38.4 mg IV hydromorphone per day = 1.6 mg/h
2. Reduce by 50% for cross-tolerance: 1.6 mg/h × 0.5 = 0.8 mg/h IV hydromorphone
3. Alternative calculation: If pain poorly controlled, start at 1.6 mg/h or increase to 2 mg/h 1

Special Population Considerations

Renal Impairment:

• Start with one-fourth to one-half the usual dose 4, 2
• Hydromorphone is safer than morphine in renal failure, but active metabolites can still accumulate 2
• Exposure increases 2-fold in moderate and 3-fold in severe renal impairment 2

Hepatic Impairment:

• Start with one-fourth to one-half the usual dose 4, 2
• Exposure increases 4-fold in moderate hepatic impairment 2
• Reduce the dose rather than extending intervals 2

Titration and Monitoring

Dose Adjustment Protocol:

• If more than 3-4 breakthrough doses per day are required, increase the scheduled baseline dose by 25-50% rather than shortening the dosing interval 2, 7
• When pain returns before the next scheduled dose, increase the dose rather than the frequency 2
• There is no advantage to increasing frequency beyond every 4 hours for immediate-release formulations 2

Monitoring Timeline:

• Monitor closely for respiratory depression, especially within the first 24-72 hours of initiating therapy 4
• Re-evaluate within 24 hours after dose adjustment, as steady state is reached within this timeframe 2
• Assess efficacy and side effects every 60 minutes for oral hydromorphone after breakthrough doses 2

Common Pitfalls to Avoid

Do Not:

• Use mixed agonist-antagonist opioids in combination with hydromorphone, as this could precipitate withdrawal 2
• Make the mistake of increasing frequency to every 3 hours—this creates non-standard dosing that increases medication errors without pharmacologic advantage 2
• Use a smaller breakthrough dose than the regular 4-hourly equivalent—the full dose is more likely to be effective 2
• Simply add more PRN doses without adjusting the scheduled regimen, as this leads to inconsistent pain control 2

Always:

• Institute prophylactic bowel regimen with stimulant laxatives, as constipation is universal with opioid therapy 2
• Monitor for myoclonus, especially with chronic use, renal failure, or dehydration 2
• Consider the quicker onset of action of hydromorphone (compared to morphine), which supports more frequent dosing intervals for optimal acute pain control 2

Conversion to Extended-Release Formulations

When Transitioning to Long-Acting Opioids:

• Calculate total 24-hour immediate-release hydromorphone requirement 1
• For extended-release hydromorphone, use a 5:1 conversion ratio from oral morphine equivalents 5, 8
• The relative bioavailability between immediate and extended-release hydromorphone is unknown, requiring close observation 4
• Most patients stabilize within 2 or fewer titration steps (mean time 4.2 days) 8