What is the equivalent dose of morphine (every 6 hours) for a patient taking 15mg of oxycodone (every 6 hours)?

Oxycodone to Morphine Conversion for Every 6 Hours Dosing

The equivalent dose of morphine for a patient taking 15mg of oxycodone every 6 hours is 22.5mg of morphine every 6 hours, based on the standard conversion factor of 1.5 for oxycodone to morphine. 1

Conversion Calculation Process

To convert from oxycodone to morphine:

1. Identify the conversion factor:

   • According to the CDC Clinical Practice Guideline (2022), oxycodone has a conversion factor of 1.5 to morphine 1
   • This means 1mg of oxycodone = 1.5mg morphine equivalent

2. Calculate the morphine equivalent dose:

   • 15mg oxycodone × 1.5 = 22.5mg morphine

3. Maintain the same dosing frequency:

   • Since the original prescription is for every 6 hours, maintain this schedule with morphine

Important Clinical Considerations

Incomplete Cross-Tolerance

• When switching between opioids, reduce the calculated dose by 25-50% to account for incomplete cross-tolerance 1
• This would mean starting with approximately 11.25-16.9mg morphine every 6 hours
• Titrate upward as needed for pain control

Patient Monitoring

• Monitor closely for signs of:
  • Inadequate pain control
  • Excessive sedation
  • Respiratory depression
  • Other opioid-related side effects

Breakthrough Pain Management

• For breakthrough pain, consider providing a rescue dose of immediate-release morphine
• The appropriate rescue dose is typically 10-20% of the total daily morphine dose 1

Pharmacological Differences

• Oxycodone has a higher oral bioavailability (60-87%) compared to morphine 2
• Oxycodone has a shorter half-life (3-5 hours) than morphine 2
• These differences may affect individual patient response to the conversion

Practical Application

When implementing this conversion:

1. Start with the reduced dose (11.25-16.9mg morphine every 6 hours)
2. Assess pain control and side effects after 24 hours
3. Titrate by 25% increments if pain control is inadequate 3
4. Consider the total daily morphine equivalent dose (MME) - for this patient, the full calculated dose would be 90mg/day (22.5mg × 4 doses)
5. Be cautious if approaching 50 MME/day, as this is a threshold for increased risk 1

Common Pitfalls to Avoid

• Using the calculated MME directly for conversion without accounting for cross-tolerance
• Failing to monitor for both under-treatment and over-treatment after conversion
• Not providing adequate breakthrough pain coverage during transition
• Assuming all patients will respond identically to the mathematical conversion

Remember that equianalgesic dose conversions are estimates and cannot account for individual variability in genetics and pharmacokinetics 1. Clinical judgment and careful monitoring remain essential when converting between opioids.