How do I convert a patient from short-acting (immediate release) opioids to long-acting (sustained release) opioids, such as morphine sulfate or oxycodone?

Converting from Short-Acting to Long-Acting Opioids

To convert a patient from short-acting to long-acting opioids, calculate the total 24-hour opioid requirement of the current short-acting medication, then convert to an equianalgesic dose of the long-acting opioid, reducing the calculated dose by 25-50% to account for incomplete cross-tolerance. 1

Step-by-Step Conversion Process

1. Calculate total daily dose of current short-acting opioid

   • Add up the total amount of short-acting opioid taken in a 24-hour period that effectively controls pain 1
   • Example: If patient takes oxycodone 10mg every 4 hours, total daily dose = 60mg/day 1

2. Convert to equianalgesic dose of desired long-acting opioid

   • Use equianalgesic conversion tables to determine equivalent dose 1
   • For oral-to-oral conversions of common opioids, use standard conversion factors 1

3. Reduce calculated dose by 25-50%

   • If pain was effectively controlled with previous opioid, reduce the equianalgesic dose by 25-50% to account for incomplete cross-tolerance 1
   • If pain was poorly controlled, may begin with 100% of equianalgesic dose or increase by up to 25% 1

4. Determine dosing schedule based on long-acting formulation

   • Divide total daily dose by appropriate number of doses (e.g., 2 doses for extended-release morphine every 12 hours) 1
   • Prescribe breakthrough medication (short-acting opioid) for the transition period 1

Specific Conversion Examples

Converting to Extended-Release Oral Morphine or Oxycodone

• Calculate total daily dose of current short-acting opioid 1
• Convert to equivalent daily dose of long-acting formulation 2, 3
• Divide by 2 for twice-daily dosing (e.g., MS Contin, OxyContin) 1
• Monitor closely for sedation during first 24-72 hours of therapy 2, 3

Converting to Transdermal Fentanyl

1. Calculate 24-hour analgesic requirement of current opioid 1
2. Convert to oral morphine equivalent if not already using morphine, oxycodone, hydromorphone, or codeine 1
3. Select appropriate fentanyl patch strength based on conversion table:
   • 60mg/day oral morphine ≈ 25mcg/h fentanyl patch
   • 120mg/day oral morphine ≈ 50mcg/h fentanyl patch
   • 180mg/day oral morphine ≈ 75mcg/h fentanyl patch
   • 240mg/day oral morphine ≈ 100mcg/h fentanyl patch 1, 4
4. Prescribe short-acting opioid for breakthrough pain, especially during first 8-24 hours 1
5. Adjust patch dosage after 2-3 days based on breakthrough medication requirements 1

Important Clinical Considerations

• Ensure pain is relatively well-controlled on short-acting opioid before initiating long-acting formulations 1
• Fentanyl patches are NOT recommended for unstable pain requiring frequent dose changes 1
• Use fentanyl patch only in opioid-tolerant patients 1
• Monitor patients closely for respiratory depression, especially within first 24-72 hours 2, 3
• Continue breakthrough medication once long-acting dose is stabilized 1
• For methadone conversions, use specialized conversion tables due to its unique properties and long half-life 1

Common Pitfalls and Caveats

• Avoid using codeine or morphine in patients with renal failure due to risk of metabolite accumulation 1
• Application of heat (fever, heating pads, electric blankets) accelerates transdermal fentanyl absorption and should be avoided 1
• Significant variability exists in equianalgesic conversion calculations between different resources 5
• Methadone conversions require special consideration due to its long and variable half-life 1
• When converting to extended-release formulations, be vigilant for excessive sedation at peak serum levels 2