About This Page
This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Opioid dependence features: tolerance, withdrawal, compulsive use, continued use despite harm
- Opioid withdrawal: NOT life-threatening (unlike alcohol) — yawning, lacrimation, rhinorrhoea, piloerection ("cold turkey"), abdominal cramps, diarrhoea, dilated pupils
- Opioid substitution therapy (OST): methadone (full agonist) or buprenorphine (partial agonist) — reduces illicit use, crime, BBV transmission, and mortality
- Naloxone: opioid antagonist for overdose reversal — IM/IV 400 mcg, repeat every 2–3 min. Short-acting (may need repeated dosing)
- Screen for blood-borne viruses: HIV, hepatitis B, hepatitis C — offer vaccination for hepatitis B
- Harm reduction: needle exchange, naloxone supply (take-home naloxone programme), safe injecting advice
Overview
Opioid use disorder encompasses harmful use and dependence on opioid substances, including heroin (diamorphine), prescribed opioids (codeine, tramadol, morphine, oxycodone, fentanyl), and illicit synthetic opioids. Dependence develops through tolerance (requiring escalating doses) and physical/psychological withdrawal on cessation. Opioids act on mu receptors to produce analgesia, euphoria, respiratory depression, and constipation. Opioid substitution therapy (OST) with methadone or buprenorphine is the cornerstone of treatment — it is evidence-based, reduces illicit drug use, criminal behaviour, blood-borne virus transmission, and mortality from overdose. The UK harm reduction approach prioritises reducing harm from drug use alongside supporting recovery.
Epidemiology
There are approximately 260,000–300,000 opioid-dependent individuals in England. The opioid-related death rate has risen significantly, with ~3,000 drug misuse deaths annually in the UK. Heroin remains the opioid most commonly associated with dependence and overdose death. Prescription opioid misuse is an increasing concern. Opioid dependence is more common in men, deprived areas, and among those with adverse childhood experiences, mental health problems, and social exclusion. Injection drug use carries risks of blood-borne virus transmission (hepatitis C: up to 50% prevalence in IV drug users; HIV), bacterial infections (endocarditis, abscesses, necrotising fasciitis), and venous disease.
Clinical Features
Symptoms
Intoxication: euphoria, drowsiness, analgesia, miosis (pinpoint pupils), respiratory depression
Withdrawal (onset 6–24h after last dose): yawning, lacrimation, rhinorrhoea, sweating, piloerection ("gooseflesh"/"cold turkey")
Withdrawal continued: abdominal cramps, diarrhoea, nausea, vomiting, muscle aches, dilated pupils, insomnia, anxiety
Compulsive drug-seeking behaviour, loss of control over use
Continued use despite harm to health, relationships, work
Overdose: respiratory depression, loss of consciousness, cyanosis — life-threatening
Signs
Intoxication: miosis (pinpoint pupils), drowsiness, respiratory depression, hypotension, bradycardia
Withdrawal: dilated pupils, tachycardia, piloerection, sweating, yawning
Track marks (injection sites), abscesses, thrombophlebitis
Features of overdose: respiratory rate <8, SpO₂ low, unresponsive, pinpoint pupils
Investigations
First-line
Urine drug screenConfirm opioid use and screen for other substances (benzodiazepines, cocaine, cannabis, amphetamines)
Blood-borne virus screenHIV, hepatitis B surface antigen, hepatitis C antibody — essential for all IV drug users
BloodsFBC, LFTs, U&Es, hepatitis B/C serology, HIV test
Second-line
ECGBaseline before starting methadone — risk of QTc prolongation (dose-dependent)
Screen for comorbidityDepression (PHQ-9), PTSD, personality disorder — very high comorbidity rates
Specialist
Specialist substance misuse assessmentComprehensive drug history, risk assessment, readiness for change, social circumstances, safeguarding
Management
NICE CG52 (Drug misuse: opioid detoxification) and NICE TA114 (Methadone and buprenorphine)1
Opioid substitution therapy (OST) — first-line for dependence
- Methadone (full mu-agonist): oral solution, starting dose 10–30 mg/day, titrated over 2 weeks to maintenance (60–120 mg/day)
- Buprenorphine (partial mu-agonist): sublingual, starting dose 4 mg, titrated to 8–24 mg/day
- Buprenorphine: must be initiated when patient is in mild withdrawal (otherwise precipitates withdrawal — partial agonist effect)
- OST reduces: illicit opioid use, overdose deaths, criminal behaviour, injection-related harm, BBV transmission
- Treatment is long-term — no pressure to detox. Supervised consumption initially, then take-home once stable
2
Opioid detoxification (if patient chooses)
- Gradual dose reduction of methadone or buprenorphine over weeks to months
- Lofexidine (alpha-2 agonist) for managing withdrawal symptoms (non-opioid alternative)
- High relapse rate after detox — psychosocial support and naltrexone can help maintain abstinence
3
Overdose management
- Naloxone: IM/IV/IN 400 mcg, repeat every 2–3 min to a max 10 mg if needed. Short half-life — patient may re-sedate
- Take-home naloxone: supply to all opioid users and their families/carers
- ABCDE approach: airway management, ventilation, oxygen. Call 999
4
Harm reduction
- Needle and syringe exchange programmes — reduce BBV transmission and injection-related harm
- Hepatitis B vaccination for all non-immune users
- Hepatitis C treatment: direct-acting antivirals — refer for treatment (cure rate >95%)
- Naloxone supply: take-home programme for overdose prevention
Complications
- Overdose death: Respiratory depression — leading cause of death. Risk increases with concurrent benzodiazepine/alcohol use and reduced tolerance after abstinence
- Blood-borne viruses: Hepatitis C (~50% in IVDU), hepatitis B, HIV — from needle sharing
- Infections: Skin abscesses, cellulitis, infective endocarditis (right-sided — tricuspid valve), septic emboli, necrotising fasciitis
- Venous damage: Thrombophlebitis, DVT, chronic venous insufficiency
- Social harm: Homelessness, unemployment, criminal activity, relationship breakdown, child safeguarding concerns
UKMLA Exam Tips
- 1Opioid intoxication: MIOSIS (pinpoint pupils) + respiratory depression + drowsiness. Opioid withdrawal: MYDRIASIS (dilated pupils) + diarrhoea + piloerection
- 2Opioid withdrawal is extremely unpleasant but NOT life-threatening (unlike alcohol withdrawal which can kill)
- 3Naloxone for overdose: short-acting — patient may re-sedate after naloxone wears off. Monitor and repeat as needed
- 4Methadone: full agonist, once daily, liquid. Buprenorphine: partial agonist, sublingual. Both are effective OST
- 5Buprenorphine must be started in WITHDRAWAL — if given while opioids still active, it precipitates withdrawal
- 6Methadone prolongs QTc — get baseline ECG. Risk of fatal arrhythmia at high doses
- 7Hepatitis C treatment: direct-acting antivirals achieve cure in >95% — all IVDU should be screened and offered treatment
practicetest your knowledge on opioid use disorderApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — psychiatry and beyond.
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