Opioid use disorder

Opioid use disorder (OUD) is a high-stakes addiction psychiatry topic across FRANZCP MEQs, MRCPsych papers and CASC stations, ABPN items, and MD/DNB vivas. Examiners test three interlocking skills: (1) emergency overdose and withdrawal management with named doses; (2) opioid agonist treatment (OAT) induction, titration and monitoring; and (3) systems thinking — harm reduction, pregnancy, dual pain, and the mortality benefit of treatment retention. Detoxification without a plan is not a moral victory if it raises fatal overdose risk.[4][11][20]

Overview and definition

OUD is a pattern of opioid use leading to clinically significant impairment or distress, operationalised in DSM-5-TR by at least 2 of 11 criteria within a 12-month period (or shorter if criteria are clustered after recent cessation). Severity: mild 2–3 criteria, moderate 4–5, severe 6 or more. Criteria span larger amounts/longer use than intended; unsuccessful cut-downs; time spent obtaining/using/recovering; craving; role failure; social problems; reduced activities; use in hazardous situations; continued use despite physical/psychological harm; tolerance; withdrawal. Tolerance and withdrawal alone do not count toward diagnosis when they occur solely during appropriate prescribed medical treatment with opioids — a classic exam discriminator against labelling every chronic pain patient as “addicted.”[14]

ICD-11 uses harmful pattern of use and dependence (with craving, impaired control, priority of use, and physiological features). State which manual you are using when coding language is examined. Physiological dependence (tolerance + withdrawal) is expected with sustained full agonists; addiction/OUD adds compulsive use, craving, and continued use despite harm.[14][20]

Classification and pharmacology map

Pharmacologic class drives both acute risk and treatment pathway choice.[10][14]

Epidemiology and risk

Global patterns of opioid use and dependence produce substantial disability and overdose mortality; prescription opioid epidemics and illicit fentanyl contamination reshape risk by region and year.[20] All-cause mortality falls during opioid substitution/agonist treatment and rises after cessation — this is the single most important public-health framing for viva and MEQ management plans.[4][13] After non-fatal opioid overdose, receipt of medication for OUD associates with reduced mortality; discharge without an offer of MOUD is a systems failure.[17]

Risk factors include early substance onset, trauma, co-occurring mental illness, chronic pain and iatrogenic exposure, social disadvantage, peer networks, and high-potency illicit supply. High-risk periods: first weeks of methadone induction if over-rapid titration; after voluntary or forced detox; after prison release; after hospital discharge without OAT restart.[4][12][13]

Pathophysiology

µ-Opioid receptor agonism inhibits pain pathways and, via disinhibition of mesolimbic dopamine, produces reward and reinforcement. Chronic exposure produces tolerance (right-shift of dose–response) and withdrawal on cessation. Locus coeruleus noradrenergic hyperactivity contributes to the sympathetic and dysphoric withdrawal syndrome — the mechanistic rationale for α2-adrenergic agonists (clonidine, lofexidine) as adjunctive withdrawal treatments.[15][20]

Buprenorphine’s partial agonism and high affinity explain both its relative respiratory safety ceiling and its ability to precipitate withdrawal if administered while full agonists still occupy receptors. Naloxone and naltrexone competitively antagonise µ-receptors — life-saving in overdose, but capable of severe precipitated withdrawal if mis-timed as “treatment.” Fentanyl’s potency and kinetics amplify overdose risk and may require repeated naloxone dosing.[10][14]

Clinical presentation

Intoxication. Euphoria or sedation, miosis, slowed speech and gait, reduced respiratory rate, constipation, pruritus. Overdose. Life-threatening triad of coma/reduced consciousness, respiratory depression, and miosis (pupils may not be pinpoint with co-ingestants or some synthetics). Cyanosis, pulmonary oedema, and death follow untreated apnoea.[10]

Withdrawal. Flu-like autonomic features: lacrimation, rhinorrhoea, yawning, mydriasis, piloerection, sweating, myalgia, abdominal cramps, diarrhoea, nausea, restlessness, anxiety, craving. Short-acting opioids (heroin, many IR pharmaceuticals): onset ~6–12 h, peak 1–3 days. Methadone withdrawal starts later and lasts longer. Withdrawal is miserable and drives relapse but is rarely directly fatal in adults — the fatal risk is return to use at lost tolerance.[3][14]

Chronic OUD. Compulsive use, injecting or other high-risk routes, neglect of roles, continued use despite harms (overdoses, infections, legal problems), and often co-occurring depression, PTSD, or pain. Examine for track marks, abscesses, and right-heart endocarditis stigmata when injecting is suspected.[20]

Differential diagnosis

Never miss medical emergencies co-travelling with overdose: head injury, hypoglycaemia, sepsis, hypoxia, and aspiration.[10]

Clinical and bedside assessment

Structure the history: opioid type(s), route, typical daily amount, last use and time, prior OAT (drug, dose, clinic), prior overdoses and naloxone use, injecting and sharing, blood-borne virus status, alcohol and other drugs (especially benzodiazepines), mental health and suicide risk, chronic pain, forensic/child protection, housing, and pregnancy potential.[14]

MSE covers consciousness, affect, craving, insight, motivation (stages of change), and risk (overdose, suicide, violence, vulnerability). Capacity is decision-specific. Involuntary treatment frameworks are jurisdiction-specific — use least-restrictive principles; do not invent foreign statute numbers.[14]

COWS — the scale you must own

The Clinical Opiate Withdrawal Scale (COWS) rates 11 domains (resting pulse; sweating; restlessness; pupil size; bone/joint aches; runny nose or tearing; GI upset; tremor; yawning; anxiety or irritability; gooseflesh). Common total-score bands used in practice: mild 5–12, moderate 13–24, moderately severe 25–36, severe greater than 36. Serial scores guide symptomatic care and, critically, whether buprenorphine induction is safe. Many protocols wait for at least mild–moderate objective withdrawal (often COWS around 8–12 or higher depending on local protocol and fentanyl exposure) before the first buprenorphine dose.[3][14]

Investigations

Bedside. Respiratory rate, SpO2, glucose, ECG when methadone planned or arrhythmia risk, pregnancy test. Labs. FBC, U&E, LFT; HIV, HBV, HCV serology; offer STI screen as indicated. Urine drug screen (UDS). Interprets recent exposure — know limits (immunoassay false positives/negatives; fentanyl and designer opioids may need specific assays; buprenorphine and methadone need their own tests). Use UDS for safety and engagement, not as a moral test.[14]

ECG / QTc. Methadone can prolong QTc and rarely associate with torsades; screen at baseline and when doses are high, symptoms appear, or interacting drugs are added (other QT-prolonging agents, CYP3A4 inhibitors). Correct electrolytes.[18]

Management — resuscitation and overdose

Immediate care. Airway positioning, bag-mask ventilation as needed, high-flow oxygen, monitor. Naloxone is a competitive µ-antagonist. Typical adult parenteral starting ranges taught in emergency care: 0.4–2 mg IV/IM/SC, repeated every few minutes to restore adequate ventilation (not necessarily full alertness — abrupt full reversal can precipitate severe withdrawal and agitation). Intranasal formulations (commonly 2–4 mg per device depending on product) enable lay and first-responder use. Infusion may be needed for long-acting opioids (methadone) or massive fentanyl exposure because naloxone’s duration can be shorter than the agonist’s.[10][14]

Observe for re-sedation. After survival, offer take-home naloxone, brief overdose education, and — where feasible — same-episode initiation of buprenorphine with assertive linkage to ongoing care. ED-initiated buprenorphine/naloxone improved engagement versus brief intervention alone in a landmark RCT.[6][12][17]

Management — definitive: OAT, antagonists, psychosocial care

Medication for OUD (MOUD/OAT) is first-line disease-modifying treatment, not a “last resort after willpower fails.” Methadone and buprenorphine maintenance reduce illicit opioid use and improve retention versus non-replacement approaches; buprenorphine is effective versus placebo and flexible-dose methadone comparisons inform choice and setting.[1][2][11][14]

Methadone (full agonist OAT)

Induction (exam-safe framing). Start low and go slow because accumulation over the first days can kill. Day-1 oral doses in many specialist protocols are often in the 10–30 mg range for patients with clear opioid tolerance (lower if low/uncertain tolerance, older age, heavy alcohol/benzo use, or respiratory disease), with careful review before additional small increments the same day. Avoid aggressive titration in week 1; peak induction toxicity often appears around days 3–7. Maintenance for most patients settles in the region of 60–120 mg orally daily, sometimes higher under specialist review if still using or craving. Supervise dosing early; unsupervised takeaways follow local regulation and stability criteria.[1][14]

Monitoring. Sedation and respiratory rate early in treatment; interactions (CYP3A4 inducers/inhibitors; sedatives); ECG/QTc as above; LFT and clinical review; pregnancy status. Missed doses may require partial restart algorithms after loss of tolerance — follow local OST guidelines.[14][18]

Buprenorphine (± naloxone)

Office-based and clinic-based buprenorphine–naloxone is effective for opiate addiction and expands access beyond methadone clinics where regulations allow.[8] Induction: wait until the patient is in adequate objective withdrawal (COWS-guided) to avoid precipitated withdrawal. Typical teaching start: 2–4 mg sublingual, reassess in ~1–2 hours, total day-1 often up toward 8 mg if tolerated (local protocols vary; fentanyl-era high-dose or micro-induction pathways exist in specialist hands). Maintenance commonly 8–24 mg sublingual daily (some jurisdictions allow up to 32 mg). Film/tablet must dissolve fully; advise against injecting diverted product. Depot/long-acting injectable buprenorphine formulations are available in some regions — know that they exist and require specialist pathways.[2][8][14]

Naltrexone

Oral naltrexone 50 mg daily (or three-times-weekly regimens in some protocols) and extended-release intramuscular naltrexone (commonly 380 mg every 4 weeks where available) require a completed opioid-free period (often ~7–10 days after short-acting opioids; longer after methadone) and ideally a negative UDS / supervised withdrawal before first dose. The X:BOT trial found that once induction succeeded, XR-naltrexone and buprenorphine–naloxone had similar effectiveness, but XR-naltrexone was harder to initiate — a key exam pearl for counselling and pathway choice.[5][14]

Withdrawal management without immediate OAT

α2-Agonists (e.g. clonidine often 0.1–0.2 mg oral every 6–8 hours with blood-pressure monitoring; lofexidine where licensed) reduce autonomic symptoms; add antiemetics, antidiarrhoeals, analgesia (non-opioid), and sleep support. Buprenorphine itself is also an evidence-based withdrawal agent. Planned detox alone has high relapse rates — always couple with overdose prevention and a maintenance offer.[15][14]

Psychosocial care and duration

Counselling and contingency frameworks support OAT but do not replace it for most severe OUD. In prescription opioid dependence, the POATS trial showed that tapering off buprenorphine after brief or extended treatment led to high relapse — favouring longer treatment rather than arbitrary short courses.[9] Duration is often years, individualised; premature taper for “clean time optics” is a classic harmful error.[4][14]

Specific subtypes and scenarios

Pharmaceutical opioid dependence. OAT is effective in pharmaceutical opioid dependence as in heroin dependence; do not withhold methadone/buprenorphine because the opioid was “only tablets.”[19][9]

Acute hospital admission. Continue existing OAT at the verified community dose after liaison with the clinic; cover opioid withdrawal if dose cannot be confirmed; do not leave patients in untreated withdrawal or uncontrolled pain.[14]

Forensic / post-release. Continuity of OAT into and out of custody plus take-home naloxone targets a known mortality spike.[12][13]

Polysubstance use. Benzodiazepines and alcohol multiply overdose risk on methadone and heroin; manage sedative use actively rather than ignoring it.[10][14]

Complications and pitfalls

Other pitfalls: diverted OAT; injecting crushed tablets; QTc ignoring interacting drugs; forced taper for administrative reasons; withholding analgesia for acute pain in patients on OAT (they may need higher short-term full-agonist doses with specialist advice while continuing buprenorphine/methadone strategy carefully); missing endocarditis; stigma that frames OAT as “replacing one addiction with another” — a viva trap to reject with evidence.[4][11][18]

Prognosis and disposition

Retention in OAT is the dominant modifiable prognostic factor for survival.[4][13] Disposition spans GP shared care, specialist drug treatment clinics, residential rehabilitation (usually after or alongside OAT stabilisation), hospital, and custody. After any non-fatal overdose, disposition planning is incomplete without a MOUD offer and naloxone supply.[17]

Special populations

Pregnancy. Opioid withdrawal risks miscarriage, preterm labour, and return to unregulated use. Maintenance agonist treatment is preferred over detoxification for dependent pregnant patients. Both methadone and buprenorphine are used; the MOTHER trial found buprenorphine-exposed neonates required less treatment for neonatal abstinence syndrome and had shorter hospital stays than methadone-exposed neonates, with important retention nuances — choice is individualised with obstetric-addiction collaboration. Cochrane synthesis supports maintenance agonist treatments in pregnancy.[7][16]

Chronic pain dual pathway. Assess OUD criteria carefully; use multimodal analgesia (non-opioid drugs, interventional and psychological pain care); if OUD is present, treat addiction with OAT while managing pain — abandonment of both pain and addiction care is the failure mode.[14][19]

Youth and older adults. Consent, family engagement, and limited licensed options in adolescents; polypharmacy, falls, and chronic disease dominate later life.[14][20]

Cultural safety. Access barriers, discrimination in healthcare, and community-controlled service models matter for Indigenous and other priority populations — FRANZCP expects culturally safe formulation, not stereotype.[20]

Evidence, guidelines, and controversies

Landmark evidence to name at viva: Mattick Cochrane reviews (methadone; buprenorphine); Sordo mortality meta-analysis; NSW pharmacotherapy cohort lives saved; Fudala office-based buprenorphine–naloxone; D’Onofrio ED initiation; Weiss POATS; Lee X:BOT; Jones MOTHER; Larochelle post-overdose MOUD; Gowing α2-agonists; ASAM 2020 guideline; Degenhardt global Lancet framing.[1][2][4][5][6][7][8][9][14][17][20]

Controversies worth a balanced sentence: supervised vs takeaway dosing balance; safe supply / prescribed diacetylmorphine in refractory cases (selected jurisdictions); fentanyl-era buprenorphine induction strategies; coerced treatment ethics.[14][20]

Exam pearls

Self-test: name doses under pressure

Methadone day-1 often 10–30 mg oral with slow titration; maintenance commonly 60–120 mg daily. Buprenorphine induction 2–4 mg SL steps after withdrawal; maintenance often 8–24 mg daily. Naloxone 0.4–2 mg parenteral repeated to ventilation; IN kits commonly 2–4 mg/device. Naltrexone oral 50 mg daily or XR-IM ~380 mg/4 weeks after detox. Clonidine ~0.1–0.2 mg q6–8h with BP checks for autonomic withdrawal.[10][14][15]

References

1. [1]Mattick RP, Breen C, Kimber J, Davoli M Methadone maintenance therapy versus no opioid replacement therapy for opioid dependence Cochrane Database Syst Rev, 2009.PMID 19588333
2. [2]Mattick RP, Breen C, Kimber J, Davoli M Buprenorphine maintenance versus placebo or methadone maintenance for opioid dependence Cochrane Database Syst Rev, 2014.PMID 24500948
3. [3]Wesson DR, Ling W The Clinical Opiate Withdrawal Scale (COWS) J Psychoactive Drugs, 2003.PMID 12924748
4. [4]Sordo L, Barrio G, Bravo MJ, Indave BI, Degenhardt L, Wiessing L, et al. Mortality risk during and after opioid substitution treatment: systematic review and meta-analysis of cohort studies BMJ, 2017.PMID 28446428
5. [5]Lee JD, Nunes EV, Novo P, Bachrach K, Bailey GL, Bhatt S, et al. Comparative effectiveness of extended-release naltrexone versus buprenorphine-naloxone for opioid relapse prevention (X:BOT): a multicentre, open-label, randomised controlled trial Lancet, 2018.PMID 29150198
6. [6]D'Onofrio G, O'Connor PG, Pantalon MV, Chawarski MC, Busch SH, Owens PH, et al. Emergency department-initiated buprenorphine/naloxone treatment for opioid dependence: a randomized clinical trial JAMA, 2015.PMID 25919527
7. [7]Jones HE, Kaltenbach K, Heil SH, Stine SM, Coyle MG, Arria AM, et al. Neonatal abstinence syndrome after methadone or buprenorphine exposure N Engl J Med, 2010.PMID 21142534
8. [8]Fudala PJ, Bridge TP, Herbert S, Williford WO, Chiang CN, Jones K, et al. Office-based treatment of opiate addiction with a sublingual-tablet formulation of buprenorphine and naloxone N Engl J Med, 2003.PMID 12954743
9. [9]Weiss RD, Potter JS, Fiellin DA, Byrne M, Connery HS, Dickinson W, et al. Adjunctive counseling during brief and extended buprenorphine-naloxone treatment for prescription opioid dependence: a 2-phase randomized controlled trial Arch Gen Psychiatry, 2011.PMID 22065255
10. [10]Boyer EW Management of opioid analgesic overdose N Engl J Med, 2012.PMID 22784117
11. [11]Volkow ND, Frieden TR, Hyde PS, Cha SS Medication-assisted therapies--tackling the opioid-overdose epidemic N Engl J Med, 2014.PMID 24758595
12. [12]Strang J, Bird SM, Parmar MK Take-home emergency naloxone to prevent heroin overdose deaths after prison release: rationale and practicalities for the N-ALIVE randomized trial J Urban Health, 2013.PMID 23633090
13. [13]Degenhardt L, Randall D, Hall W, Law M, Butler T, Burns L Mortality among clients of a state-wide opioid pharmacotherapy program over 20 years: risk factors and lives saved Drug Alcohol Depend, 2009.PMID 19608355
14. [14]American Society of Addiction Medicine The ASAM National Practice Guideline for the Treatment of Opioid Use Disorder: 2020 Focused Update J Addict Med, 2020.PMID 32511106
15. [15]Gowing L, Farrell M, Ali R, White JM Alpha₂-adrenergic agonists for the management of opioid withdrawal Cochrane Database Syst Rev, 2016.PMID 27140827
16. [16]Minozzi S, Amato L, Jahanfar S, Bellisario C, Ferri M, Davoli M Maintenance agonist treatments for opiate-dependent pregnant women Cochrane Database Syst Rev, 2020.PMID 33165953
17. [17]Larochelle MR, Bernson D, Land T, Stopka TJ, Wang N, Xuan Z, et al. Medication for Opioid Use Disorder After Nonfatal Opioid Overdose and Association With Mortality: A Cohort Study Ann Intern Med, 2018.PMID 29913516
18. [18]Krantz MJ, Martin J, Stimmel B, Mehta D, Haigney MC QTc interval screening in methadone treatment Ann Intern Med, 2009.PMID 19153406
19. [19]Nielsen S, Larance B, Degenhardt L, Gowing L, Kehler C, Lintzeris N Opioid agonist treatment for pharmaceutical opioid dependent people Cochrane Database Syst Rev, 2016.PMID 27157143
20. [20]Degenhardt L, Grebely J, Stone J, Hickman M, Vickerman P, Marshall BDL, et al. Global patterns of opioid use and dependence: harms to populations, interventions, and future action Lancet, 2019.PMID 31657732