How do I convert morphine to oxycodone?

Converting Morphine to Oxycodone

To convert morphine to oxycodone, use a conversion ratio of 1:1.5, meaning that 1 mg of morphine is equivalent to 0.67 mg of oxycodone (or multiply the morphine dose by 0.67 to get the oxycodone dose). 1

Conversion Process

1. Calculate the total daily morphine dose
2. Multiply the morphine dose by 0.67 (or divide by 1.5) to get the equianalgesic oxycodone dose
3. Reduce the calculated oxycodone dose by 25-50% to account for incomplete cross-tolerance
4. Divide the total daily oxycodone dose into appropriate dosing intervals based on formulation

Detailed Algorithm

Step 1: Calculate Total Daily Morphine Dose

• Add up all regular and as-needed morphine doses taken in 24 hours
• For extended-release formulations, include the full daily amount

Step 2: Apply Conversion Factor

• According to CDC guidelines, the morphine milligram equivalent (MME) conversion factor for oxycodone is 1.5 1
• Therefore: Oxycodone dose = Morphine dose ÷ 1.5

Step 3: Adjust for Cross-Tolerance

• If pain was well-controlled on morphine, reduce the calculated oxycodone dose by 25-50% 1
• If pain was not well-controlled, use 100% of the calculated dose or even increase by 25% 1

Step 4: Determine Dosing Schedule

• For immediate-release oxycodone: Divide total daily dose into portions given every 4-6 hours 2
• For extended-release oxycodone: Divide total daily dose into two equal doses given every 12 hours 2

Example Conversion

For a patient taking 60 mg of oral morphine daily:

1. Calculate equianalgesic dose: 60 mg morphine ÷ 1.5 = 40 mg oxycodone
2. Adjust for cross-tolerance (assuming good pain control): 40 mg × 0.75 = 30 mg oxycodone daily
3. For immediate-release: 5 mg every 4 hours or 7.5 mg every 6 hours
4. For extended-release: 15 mg every 12 hours

Important Considerations

• Individual variability: Patient response to different opioids varies significantly, with 10-30% of patients not responding well to morphine but potentially responding better to oxycodone 1

• Monitoring: Closely monitor for both efficacy and side effects during the first 24-48 hours after conversion

• Breakthrough pain: Provide immediate-release oxycodone for breakthrough pain (typically 10-15% of the total daily dose)

• Titration: After initial conversion, titrate the dose based on patient response to achieve adequate analgesia with minimal side effects 2

• Risk factors: Use caution in elderly patients and those with renal or hepatic impairment

Common Pitfalls to Avoid

• Overestimation: Converting directly using equianalgesic tables without accounting for cross-tolerance can lead to overdosing

• Undertreatment: Excessive dose reduction may lead to inadequate pain control

• Failing to individualize: While conversion ratios provide a starting point, clinical judgment is essential to adjust based on patient response

• Abrupt discontinuation: Always taper morphine gradually while introducing oxycodone to prevent withdrawal symptoms

Remember that these conversion ratios are estimates and careful monitoring is essential to ensure optimal pain control with minimal adverse effects.