opioid use disorder

opioid use disorder

a chronic, relapsing disorder characterized by problematic pattern of opioid use leading to clinically significant impairment or distress. 2024 CMAJ / CRISM Guidelines, emphasize a continuum of care that includes harm reduction and patient-centered treatment goals.

diagnosis (DSM-5-TR)

• Criteria: Problematic pattern of use leading to impairment/distress with $\ge 2$ of 11 criteria in 12 months (e.g., tolerance, withdrawal, larger amounts than intended, cravings, social/occupational neglect).
• Severity: Mild (2–3), Moderate (4–5), Severe ($\ge 6$).

management framework (cmaj 2024)

1. First-Line Therapy: Buprenorphine/Naloxone OR Methadone (Both are now considered first-line).
2. Second-Line Therapy: Slow-Release Oral Morphine (SROM) (Kadian).
3. Harm Reduction: Must be offered to all patients (Naloxone kits, sterile supplies, overdose prevention sites).
4. Psychosocial: CBT/counselling should be offered as adjunct but not mandatory for accessing medication.
5. Withdrawal Management: Avoid as stand-alone treatment (high relapse/overdose risk). Only use if connecting to long-term follow-up.

pharmacotherapy

first-line agents

drug	Buprenorphine / Naloxone (Suboxone)	Methadone
Mechanism	Partial $\mu$-agonist with high affinity (blocks other opioids). Naloxone added to prevent injection (poor PO bioavailability).	Full $\mu$-agonist (L-enantiomer) and NMDA antagonist (S-enantiomer).
Key Features	”Ceiling effect” (safer overdose profile). Can be taken home immediately. Also available as Sublocade (SC depot q28d).	No ceiling effect (good for high tolerance). Requires daily witnessed dosing initially. QT Prolongation risk.
Induction	Precipitated Withdrawal Risk: Must be in moderate withdrawal (COWS score > 12) before starting (12–24h opioid free).	Can start immediately (no need to wait for withdrawal).
Safety	Lower risk of respiratory depression.	Higher risk of overdose during first month (titration phase).
Notes	If injected, the Naloxone component precipitates withdrawal. Taken SL/PO, Naloxone is inert.	Requires specific exemption/license to prescribe in some jurisdictions.

second-line & alternative agents

• Slow-Release Oral Morphine (SROM):
  • Role: Second-line option if Buprenorphine/Methadone ineffective or contraindicated.
  • Form: 24-hour sustained release formulation (e.g., Kadian).
• Oral Naltrexone:
  • Status: Special Consideration (not first-line).
  • Mechanism: Competitive $\mu$-antagonist.
  • Use: Highly motivated patients or those unable to take agonists (e.g., employment restrictions).
  • Critical: Must be opioid-free for 7–10 days to avoid severe precipitated withdrawal.
  • Benefit: Also treats Alcohol Use Disorder.

harm reduction & special populations

• Harm Reduction:
  • Take-home Naloxone kits.
  • Safe consumption sites / Overdose prevention services.
  • Needle exchange programs (reduces HIV/HCV).
• Pregnancy:
  • Buprenorphine or Methadone are both safe and recommended.
  • Avoid withdrawal management (risk of fetal distress/miscarriage).
• Withdrawal Management:
  • “Detox” alone has very high rates of relapse and subsequent overdose (loss of tolerance). Always link to long-term agonist therapy.

precipitated withdrawal

Occurs when a partial agonist (Buprenorphine) or antagonist (Naltrexone) displaces a full agonist (Heroin/Fentanyl) from the $\mu$-receptor.

• Symptoms: Rapid onset severe pain, vomiting, diarrhea, agitation.
• Prevention: Use COWS (Clinical Opioid Withdrawal Scale) to ensure patient is in sufficient withdrawal before starting Buprenorphine.

related pages: Alcohol Use Disorder, Naltrexone, Methadone