Substance use disorder, including relapse prevention and acute withdrawal from - opioids

Description

Opioid use disorder - compulsive use despite harm, tolerance, withdrawal on cessation
DSM-5-TR: 2+ of 11 criteria over 12 months
Withdrawal is distressing but not life-threatening (unlike alcohol/benzodiazepine withdrawal)
Overdose is the life-threatening complication - respiratory depression

Rising heroin and pharmaceutical opioid (oxycodone, fentanyl) related harm and overdose deaths in Australia
Opioid-related deaths now exceed heroin-specific deaths - pharmaceutical opioids and illicit fentanyl contamination major drivers
Neonatal abstinence syndrome in opioid-exposed pregnancies

Chronic mu-opioid receptor agonism -> receptor downregulation/tolerance
Abrupt cessation -> unopposed noradrenergic surge (locus coeruleus) -> withdrawal syndrome
Overdose: mu-receptor mediated respiratory centre depression -> hypoventilation, hypoxia, death
Illicit fentanyl/nitazene contamination -> potency unpredictability, higher overdose risk even in tolerant users

Clinical - DSM-5-TR criteria, collateral history
Withdrawal: COWS (Clinical Opiate Withdrawal Scale) - objective score guides buprenorphine induction timing
Withdrawal features: dilated pupils, piloerection, rhinorrhoea, lacrimation, cramps, diarrhoea, yawning, myalgia - onset 6-12h (short-acting) to 24-48h (methadone) after last use
Urine drug screen supportive but not diagnostic alone

1. Overdose (acute)

Naloxone IM/IN, titrate to adequate ventilation not full arousal (avoids precipitating acute withdrawal)
Take-home naloxone free and available without prescription in Australia - offer to all at-risk patients and their contacts
Repeat dosing may be needed for long-acting opioids (methadone, extended-release oxycodone) given naloxone's short half-life

2. Opioid agonist treatment (OAT) - mainstay of relapse prevention

Buprenorphine (+/- naloxone combination): partial agonist, ceiling effect -> safer in overdose
- Induction requires objective withdrawal (COWS >=8-12) before first dose to avoid precipitated withdrawal
- Long-acting depot buprenorphine formulations now widely used - improves adherence
Methadone: full agonist, daily supervised dosing, requires careful titration (long/variable half-life -> accumulation risk, QT prolongation)
Both require authorised prescriber/program enrolment in Australia

3. Psychosocial

Counselling, contingency management, peer support, harm reduction (needle syringe programs)

4. Withdrawal management (if not proceeding to OAT)

Symptomatic: clonidine (autonomic symptoms), loperamide, antiemetics, NSAIDs
Not life-threatening but high relapse/overdose risk if abstinence attempted without OAT

Chronic relapsing course; OAT substantially reduces mortality, overdose and criminal activity vs abstinence-only approaches
Overdose risk highest after a period of abstinence (detox, incarceration, rehab) due to lost tolerance - counsel explicitly on this before any planned cessation
Long-term OAT (years, sometimes lifelong) more effective than short courses

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