What is the equivalent dose of methadone for a patient taking 15 mg of oxycodone (oxycondone) three times a day (tid)?

Converting 15 mg Oxycodone TID to Methadone

The equivalent dose of methadone for a patient taking 15 mg of oxycodone three times daily is approximately 10-15 mg of methadone total daily dose, divided into 3-4 doses per day. 1, 2

Step-by-Step Conversion Process

1. Calculate Total Daily Oxycodone Dose

• Oxycodone 15 mg × 3 times daily = 45 mg total daily dose

2. Convert to Morphine Equivalent Dose (MED)

• Using the conversion factor from CDC guidelines: oxycodone 1.5 × morphine 1
• 45 mg oxycodone × 1.5 = 67.5 mg oral morphine equivalent

3. Determine Appropriate Morphine-to-Methadone Conversion Ratio

• For morphine equivalent doses between 30-90 mg, the National Comprehensive Cancer Network recommends a variable conversion ratio 1, 2
• Since our calculated dose (67.5 mg) falls within this range, we use a ratio of approximately 4:1 to 6:1

4. Calculate Initial Methadone Dose

• 67.5 mg morphine ÷ 4 to 6 = approximately 11-17 mg methadone per day

5. Apply Safety Reduction

• Reduce calculated dose by 25-50% to account for incomplete cross-tolerance 1, 2
• 11-17 mg × 0.75 (25% reduction) = approximately 8-13 mg methadone per day
• Final recommended dose: 10-15 mg methadone total daily dose

6. Divide into Multiple Daily Doses

• Divide total daily methadone dose into 3-4 doses per day 1, 2
• Approximately 3-5 mg methadone every 8 hours (for TID dosing)

Important Considerations and Precautions

Methadone's Unique Pharmacology

• Methadone has a long and variable half-life (15-60 hours) 2
• Risk of accumulation with repeated dosing
• Peak respiratory depression may occur later than peak analgesic effect 2

Monitoring Requirements

• Assess pain control and side effects daily for the first week 2
• Watch for signs of oversedation or respiratory depression
• Consider ECG monitoring for QTc prolongation, especially if:
  • Doses exceed 100 mg/day
  • Patient has cardiac risk factors
  • Patient takes other medications that prolong QTc 1, 2

Dose Titration

• Increase methadone doses no more frequently than every 5-7 days 1, 2
• Typical increases of 5-10 mg per dose
• Provide rescue doses of immediate-release opioid during transition if needed 2

Common Errors to Avoid

• Using fixed conversion ratios without considering total daily dose 2
• Titrating methadone too quickly (accumulation may not be apparent for days) 2
• Not monitoring for cardiac effects in at-risk patients 1, 2

This conversion requires careful monitoring due to methadone's complex pharmacokinetics and potential for delayed toxicity. The conversion ratio varies based on the patient's prior opioid exposure, with higher morphine equivalent doses requiring higher conversion ratios.