8.4 Substance Use Disorders, Withdrawal Syndromes, & Harm Reduction
Key Takeaways
- Canadian CRISM guidelines recommend Buprenorphine-Naloxone as the first-line Opioid Agonist Therapy (OAT) for Opioid Use Disorder due to its favorable safety profile and lower risk of fatal overdose.
- Severe alcohol withdrawal can progress to Delirium Tremens (48-96h post-ingestion) marked by delirium, autonomic hyperactivity, and fever; treatment involves symptom-triggered benzodiazepines (diazepam, or lorazepam in hepatic impairment).
- Thiamine (Vitamin B1) must always be administered BEFORE or concurrently with IV glucose in patients with alcohol use disorder to prevent precipitating acute Wernicke's Encephalopathy.
- First-line relapse prevention pharmacotherapy for Alcohol Use Disorder includes Naltrexone (contraindicated in acute hepatitis or opioid use) and Acamprosate (safe in liver disease, dose-adjusted in renal impairment).
- Canadian harm reduction strategies emphasize low-barrier access to Take-Home Naloxone (THN) kits, Supervised Consumption Services (SCS), and drug checking to reduce drug toxicity deaths.
8.4 Substance Use Disorders, Withdrawal Syndromes, & Harm Reduction
Substance use disorders (SUD) are chronic, relapsing medical conditions characterized by compulsive drug seeking and use despite harmful consequences. Management in Canada integrates evidence-based withdrawal protocols, long-term pharmacotherapy, and a comprehensive public health harm reduction model.
Alcohol Use Disorder & Withdrawal Protocols
Clinical Assessment & CIWA-Ar Scale
Alcohol withdrawal occurs when chronic ethanol suppression of central nervous system (CNS) $\text{GABA}_A$ receptors and enhancement of NMDA receptors is abruptly removed, causing severe glutamate-driven neuroexcitation.
The Clinical Institute Withdrawal Assessment for Alcohol, Revised (CIWA-Ar) scale monitors withdrawal severity across 10 domains (nausea, tremor, paroxysmal sweats, anxiety, agitation, tactile/auditory/visual disturbances, headache, orientation).
Alcohol Withdrawal Timeline & Features
Withdrawal Progression:
6 - 12 Hours: Minor Withdrawal (Tremor, anxiety, tachycardia, sweating)
12 - 48 Hours: Withdrawal Seizures (Generalized tonic-clonic)
12 - 48 Hours: Alcoholic Hallucinosis (Visual/auditory, CLEAR sensorium)
48 - 96 Hours: Delirium Tremens (DTs: Delirium, autonomic instability, fever, 5% mortality)
Pharmacological Management of Alcohol Withdrawal
- First-Line Therapy: Benzodiazepines act as $\text{GABA}_A$ agonists to suppress withdrawal hyperexcitability.
- Long-acting agents (Preferred): Diazepam or Chlordiazepoxide provide smooth self-tapering and lower risk of breakthrough seizures.
- Short/Intermediate-acting agents: Lorazepam, Oxazepam, Temazepam (mnemonic LOT) are preferred in patients with hepatic impairment, advanced age, or severe respiratory compromise because they undergo direct glucuronidation without active hepatic metabolites.
- Thiamine Administration: Thiamine (Vitamin B1) 200–500 mg IV must be administered BEFORE or concurrently with any glucose/dextrose infusion to prevent precipitating acute Wernicke's Encephalopathy (triad: confusion, ataxia, ophthalmoplegia/nystagmus). If untreated, it progresses to irreversible Korsakoff Syndrome (confabulation, anterograde amnesia).
Relapse Prevention Pharmacotherapy for Alcohol Use Disorder
- Naltrexone (First-Line): Oral $\mu$-opioid receptor antagonist that reduces alcohol craving and heavy drinking reinforcement. Contraindicated in patients taking opioids or with acute hepatitis/liver failure.
- Acamprosate (First-Line): NMDA receptor antagonist that restores glutamate homeostasis. Safe in hepatic impairment; excreted renally (requires dose reduction in renal impairment).
- Disulfiram (Second-Line): Aldehyde dehydrogenase inhibitor causing accumulation of acetaldehyde upon alcohol ingestion (flushing, nausea, vomiting, throbbing headache). Requires high patient motivation and adherence.
Opioid Use Disorder (OUD) & Harm Reduction Guidelines
Acute Opioid Toxicity & Overdose
- Classic Triad: CNS depression / coma, miosis (pinpoint pupils), and respiratory depression ($\text{RR} < 10/\text{min}$).
- Emergency Management: Airway protection, oxygenation, and immediate Naloxone (IV, IM, SC, or Intranasal). Goal of naloxone is restoring adequate spontaneous respiration, not full arousal, to avoid precipitating acute severe opioid withdrawal.
Opioid Agonist Therapy (OAT) — Canadian Guidelines (CRISM)
The Canadian Research Initiative in Substance Misuse (CRISM) guidelines establish clear evidence-based hierarchies for OAT in OUD:
| OAT Line | Medication | Mechanism & Clinical Properties | Administration & Safety Features |
|---|---|---|---|
| First-Line | Buprenorphine - Naloxone (Suboxone) | Partial $\mu$-opioid agonist + antagonist (Naloxone). High affinity, ceiling effect on respiratory depression. | Sublingual administration. Naloxone has minimal oral bioavailability; if crushed and injected, naloxone blocks opioid receptors, discouraging IV misuse. Unsupervised home dosing is safe early in treatment. |
| Second-Line | Methadone | Full $\mu$-opioid agonist with long, variable half-life. No ceiling effect. | Oral solution. Requires daily witnessed ingestion at pharmacy initially. Risks: Overdose during induction, QTc prolongation (requires baseline ECG), extensive CYP3A4 interactions. |
| Third-Line | Sustained-Release Oral Morphine (SROM / Kadian) | 24-hour slow-release full $\mu$-opioid agonist. | Prescribed when buprenorphine and methadone fail or are intolerable. Witnessed daily ingestion. |
CRITICAL EXAM TRAP — Precipitated Withdrawal: Buprenorphine has a very high binding affinity for $\mu$-opioid receptors. If administered to a patient with active full-agonist opioids in their system, buprenorphine will displace the full agonist and precipitate acute severe withdrawal. Buprenorphine induction must be delayed until the patient demonstrates objective mild-to-moderate withdrawal symptoms (COWS score $\ge 8-12$).
Canadian Harm Reduction Framework
Harm reduction aims to reduce negative health and social consequences associated with substance use without requiring abstinence:
- Take-Home Naloxone (THN) Kits: Distributed free of charge across Canadian pharmacies and community centers.
- Supervised Consumption Services (SCS) / Overdose Prevention Sites (OPS): Provide hygienic spaces, sterile supplies, overdose management, and referrals to treatment.
- Drug Checking Services: Utilizing mass spectrometry or test strips to identify fentanyl and toxic adulterants (e.g., nitazenes, xylazine).
Other Substance Withdrawal Profiles
Common Substance Withdrawal Symptoms:
Benzodiazepines: Anxiety, tremors, seizures, delirium (life-threatening, slow taper required)
Cannabis: Irritability, insomnia, decreased appetite, anxiety (supportive care)
Stimulants (Cocaine/Amphetamines): "Crash" depression, hyperphagia, vivid dreams (suicide risk monitoring)
- Benzodiazepine Withdrawal: Similar to alcohol withdrawal, characterized by rebound anxiety, tremor, autonomic instability, and life-threatening seizures. Requires a slow, structured outpatient taper using long-acting benzodiazepines (e.g., Diazepam).
- Stimulant Withdrawal (Cocaine / Methamphetamine): Characterized by severe mood "crash", intense craving, fatigue, hyperphagia, psychomotor retardation, and suicidal ideation. Treatment is supportive; no specific FDA/Health Canada-approved pharmacotherapy.
According to Canadian Research Initiative in Substance Misuse (CRISM) guidelines, what is the recommended first-line Opioid Agonist Therapy (OAT) for Opioid Use Disorder?
A 52-year-old male with a history of severe alcohol use disorder is admitted to the medical ward. On day 3 of admission, he becomes severely disoriented, agitated, diaphoresis, tachycardic (HR 130 bpm), and reports seeing insects crawling on the walls. What is the most appropriate pharmacotherapy?
A 48-year-old homeless male with chronic alcohol use disorder presents to the emergency department confused and uncooperative. On physical exam, he exhibits horizontal nystagmus, bilateral abducens nerve palsy, and a wide-based ataxic gait. Which medication must be administered before or alongside intravenous dextrose?