23.2 Chronic Pain Management, Medication-Assisted Therapy & the Opioid-Tolerant Patient

Why This Topic Matters on the NCE

Two separate parts of the content outline converge here: Domain III.L.2.b, chronic pain management, and Domain IV.B.5, the substance use disorder population including medication-assisted therapy, pharmacologic interactions, pain management, and management of complications. The opioid-tolerant surgical patient is the single most common place these two domains meet, and getting it wrong produces either uncontrolled agony or a respiratory arrest.

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1. Non-Opioid Foundations of Chronic Pain Management

Infusion adjuvants used perioperatively

• Ketamine: a bolus of 0.25 to 0.5 mg/kg followed by an infusion of roughly 0.1 to 0.3 mg/kg/h reliably reduces opioid consumption and is most valuable in the opioid-tolerant patient.
• Lidocaine: 1 to 2 mg/kg bolus then 1 to 2 mg/kg/h, best supported in open and laparoscopic abdominal surgery within enhanced recovery pathways. Do not combine with a large-volume regional block without accounting for total local anesthetic dose.
• Dexmedetomidine: 0.2 to 0.7 mcg/kg/h, opioid sparing without respiratory depression.
• Methadone: a single intraoperative dose of roughly 0.1 to 0.3 mg/kg provides prolonged analgesia through combined mu agonism and NMDA antagonism. Watch for QT prolongation and remember its long and variable half-life of 15 to 60 hours.

Regional anesthesia and analgesia is first-line for the opioid-tolerant patient whenever the surgery permits it.

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2. The Opioid-Tolerant Surgical Patient

Core principle

Continue the baseline opioid requirement and treat the acute surgical pain on top of it. The single most common and most dangerous error is stopping the home opioid at admission, which produces withdrawal and leaves the acute pain untreated.

• Verify the home regimen with the prescriber, the pharmacy, or the prescription drug monitoring program.
• Expect acute opioid requirements 30 to 100 percent above those of an opioid-naive patient for the same operation.
• Do not rely on as-needed dosing alone. Use scheduled baseline dosing plus patient-controlled analgesia with a higher demand dose, and consider a background infusion in the genuinely tolerant patient.
• Avoid agonist-antagonists and partial agonists — nalbuphine, butorphanol, and buprenorphine given acutely to a patient on a full agonist will displace it and precipitate withdrawal and severe pain.

Equianalgesic conversion

When converting between opioids, reduce the calculated dose by 25 to 50 percent to account for incomplete cross-tolerance, then titrate up. Methadone conversion is nonlinear and dose dependent and should not be estimated with a simple ratio.

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3. Medication-Assisted Therapy: The Three Drugs

Buprenorphine

A partial mu agonist with very high receptor affinity and slow dissociation. It has a ceiling on respiratory depression but not on analgesia, and its high affinity means full agonists cannot easily displace it.

Historic practice was to stop buprenorphine 72 hours before surgery. Current consensus guidance from ASRA, the American Society of Addiction Medicine, and allied societies recommends continuing buprenorphine perioperatively for most patients, because discontinuation destabilizes recovery, risks relapse and overdose death, and is not required for adequate analgesia.

• Continue the home dose, or divide it into two or three daily doses to exploit its analgesic duration.
• Add titrated full agonists, regional anesthesia, ketamine, and non-opioid multimodal therapy on top. Higher full-agonist doses may be needed to compete for receptors, so monitor accordingly.
• Consider dose reduction only for very high doses in consultation with the prescriber, and never abruptly.

Methadone (for opioid use disorder)

A full mu agonist with NMDA antagonism and a long, variable half-life.

• Continue the maintenance dose and verify it directly with the opioid treatment program — federal regulation governs these programs and the dose must be confirmed, not assumed.
• Critically, the once-daily maintenance dose provides no meaningful acute analgesia, because the analgesic duration is only 6 to 8 hours while the dosing interval is 24 hours. Additional short-acting opioid is required for surgical pain.
• QT prolongation and torsades risk; check an ECG when combining with other QT-prolonging drugs.

Naltrexone

A full mu antagonist — the mirror-image problem. Opioids will not work.

• Oral naltrexone: discontinue at least 72 hours before elective surgery.
• Extended-release injectable naltrexone (monthly depot): schedule elective surgery at least 30 days after the last injection.
• After any period off naltrexone the patient is opioid-naive and highly sensitive — receptor upregulation means standard doses can cause respiratory arrest.
• For emergency surgery in a naltrexone-blocked patient, plan a non-opioid strategy: regional anesthesia, ketamine, dexmedetomidine, lidocaine infusion, acetaminophen and NSAIDs, and high-dependency monitoring if high-dose opioid is used to overcome the blockade.

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4. Practical Perioperative Algorithm

1. Identify and verify all chronic opioid, buprenorphine, methadone, and naltrexone therapy preoperatively.
2. Continue baseline therapy; never stop it at the door.
3. Choose a regional technique whenever the surgery allows.
4. Load multimodal non-opioids: acetaminophen, an NSAID if permitted, a gabapentinoid where appropriate, dexamethasone.
5. Add ketamine, lidocaine, or dexmedetomidine infusions intraoperatively.
6. Anticipate substantially higher opioid requirements and use scheduled plus patient-controlled dosing.
7. Monitor for sedation and respiratory depression with capnography in the high-risk patient.
8. Communicate a clear discharge plan with the prescriber and avoid discharging on an escalated long-term regimen.

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Exam Traps

• Do not stop buprenorphine. Current guidance is to continue it and add full agonists.
• Maintenance methadone is not analgesia. Additional short-acting opioid is required.
• Extended-release naltrexone needs 30 days, oral naltrexone 72 hours.
• Never give nalbuphine or butorphanol to a patient on chronic full agonists — precipitated withdrawal.
• Reduce by 25 to 50 percent when converting between opioids for incomplete cross-tolerance.