What is the appropriate use of methadone (opioid analgesic) in postoperative pain management?

Methadone in Postoperative Pain Management

Methadone should be used as an effective component of multimodal analgesia for postoperative pain management, with continued administration of the patient's daily methadone maintenance dose plus additional opioid analgesics when indicated for acute pain control. 1

General Principles for Methadone Use in Postoperative Pain

For Opioid-Naive Patients

• Intraoperative administration of methadone provides superior analgesia compared to other opioids, with benefits lasting up to 72 hours postoperatively 2
• A single intraoperative dose (0.2-0.3 mg/kg) can reduce:
  • Postoperative pain scores at rest and with movement
  • Postoperative opioid consumption
  • Potential for development of chronic postsurgical pain 3

For Patients on Methadone Maintenance Therapy

1. Continue the patient's daily methadone maintenance dose throughout the perioperative period 1
2. Verify the maintenance dose with the methadone maintenance program
3. Notify the methadone program at hospital admission and discharge
4. Administer additional short-acting opioid analgesics when indicated for acute pain control 4

Route of Administration

• Oral route should be preferred whenever feasible 1
• If oral intake is not possible, convert to parenteral administration:
  • Intramuscular or subcutaneous methadone should be given as half to two-thirds the maintenance dose
  • Divide into 2-4 equal doses throughout the day 1
• Avoid intramuscular route for postoperative pain management in general 1
• Patient-controlled analgesia (PCA) with methadone is effective and may provide better analgesia with less opioid consumption compared to morphine PCA 5

Dosing Considerations

For Opioid-Naive Patients

• For intraoperative use: 0.2-0.3 mg/kg as a single dose at the beginning of surgery 2, 3
• For postoperative PCA: Methadone PCA results in less opioid consumption and lower pain scores compared to morphine PCA 5

For Opioid-Tolerant Patients

• Higher doses of opioid analgesics will likely be required due to tolerance 4
• When converting from other opioids to methadone, use FDA conversion tables based on total daily morphine dose 4:
  • For morphine doses <100 mg/day: IV methadone 10-15% of oral morphine dose
  • For morphine doses 100-300 mg/day: IV methadone 5-10% of oral morphine dose
  • For morphine doses 300-600 mg/day: IV methadone 4-6% of oral morphine dose

Multimodal Approach

Combine methadone with:

1. Non-opioid analgesics 1:

   • Acetaminophen (first-line, administer at beginning of postoperative period)
   • NSAIDs (if no contraindications)
   • COX-2 inhibitors (if no contraindications)

2. Regional anesthesia techniques 1:

   • Epidural analgesia when appropriate
   • Peripheral nerve blocks
   • Local anesthetic infiltration

3. Adjuvant medications 1:

   • Gabapentinoids (pregabalin, gabapentin)
   • Alpha-2-agonists (dexmedetomidine)
   • Ketamine (subanesthetic doses)

Special Considerations

For Patients on Buprenorphine Maintenance

Due to buprenorphine's high affinity for μ-receptors, management options include 1:

1. Continue buprenorphine and titrate short-acting opioid analgesics to effect (may require higher doses)
2. Divide daily buprenorphine dose and administer every 6-8 hours
3. For patients on doses >12 mg, consider tapering to 12 mg 2-3 days before surgery 1

Monitoring Requirements

• Monitor level of consciousness and respiratory status frequently
• Have naloxone readily available
• For high-risk patients, consider more intensive monitoring settings

Common Pitfalls and Caveats

1. Avoid mixed agonist-antagonist opioids (pentazocine, nalbuphine, butorphanol) in patients on methadone maintenance as they may precipitate withdrawal 1

2. Avoid combination products with fixed doses of acetaminophen and opioids in patients requiring large doses to prevent acetaminophen toxicity 1

3. Be aware of QT prolongation risk with methadone, especially with concomitant medications that:

   • Prolong QT interval (class I and III antiarrhythmics, some neuroleptics, tricyclic antidepressants)
   • Induce electrolyte disturbances (diuretics, laxatives) 6

4. Do not confuse anxiety symptoms with withdrawal symptoms in methadone maintenance patients 6

5. Remember that maintenance methadone dose does not provide analgesia for acute pain; additional analgesics are required 4, 6