Substance Misuse
Alcohol, opioid and drug misuse — clinical management and prescribing
Substance misuse encompasses harmful or dependent use of alcohol, opioids, cannabis, stimulants, and other substances. It is a major public health concern in the UK, associated with significant morbidity, mortality, and social harm. Effective clinical management requires a combination of pharmacological treatment, psychological support, and harm reduction.
Overview
Substance misuse refers to the use of alcohol or drugs in a way that is harmful to the individual or others. Dependence is characterised by compulsive use, tolerance, withdrawal symptoms, and continued use despite harm. The biopsychosocial model recognises that substance misuse arises from a complex interaction of genetic vulnerability, mental health, trauma, social deprivation, and environmental factors. Comorbid mental illness (dual diagnosis) is extremely common — up to 75% of people with severe substance misuse have a co-occurring mental health condition. Assessment should include CAGE questionnaire for alcohol (2+ positive answers suggests harmful use), AUDIT score, and COWS/CIWA-Ar for severity of opioid and alcohol withdrawal respectively.
Alcohol misuse
The AUDIT (Alcohol Use Disorders Identification Test) score ≥8 indicates hazardous drinking; ≥16 suggests harmful drinking; ≥20 indicates possible dependence. CAGE score ≥2 suggests clinically significant alcohol problems. The CIWA-Ar (Clinical Institute Withdrawal Assessment for Alcohol) is used to grade severity of alcohol withdrawal. Alcohol withdrawal can cause seizures, delirium tremens, and Wernicke's encephalopathy — a medical emergency requiring IV thiamine. Community detox requires daily contact and support. Inpatient detox is indicated if there is a history of seizures, previous complicated withdrawal, Wernicke's risk, severe dependence, or failure of community detox. Following detox, relapse prevention medication may be considered alongside psychological support.
Opioid misuse
Opioid substitution therapy (OST) is the evidence-based treatment for opioid dependence. Both methadone and buprenorphine/naloxone (Suboxone) are used — the choice depends on clinical factors, patient preference, and setting. OST reduces illicit drug use, criminal activity, and overdose deaths. Supervised consumption is standard initially, with dispensing frequency reduced as stability improves. Take-home naloxone (an opioid overdose reversal agent) should be offered to all patients on OST and their close contacts. Treatment is typically initiated and monitored by specialist drug and alcohol services.
Cannabis & stimulant misuse
A structured evaluation of cannabis and stimulant use should assess frequency, quantity, route, triggers, and impact on mental health and daily functioning. Cannabis: there is no licensed pharmacotherapy for cannabis dependence. High-potency cannabis (skunk) is associated with psychosis, especially in adolescents. Management includes motivational interviewing, CBT, and psychoeducation. Cannabis withdrawal causes irritability, insomnia, and reduced appetite — typically resolves within 2 weeks. Stimulants (cocaine, MDMA, amphetamines): no licensed replacement therapy. Cocaine dependence can cause severe cardiovascular complications (MI, stroke, arrhythmia). Cocaine-induced chest pain should be treated with GTN and benzodiazepines — beta-blockers are contraindicated. Crack cocaine: high dependence potential; community-based intervention is key. Crystal methamphetamine is associated with severe dental disease, psychosis, and cardiovascular complications.
Harm reduction principles
Harm reduction acknowledges that not all patients are ready to stop using substances and that reducing harm is a valid and important goal. Core harm reduction interventions include: needle and syringe programmes (NSP) to reduce blood-borne virus transmission (hepatitis B, C, HIV); hepatitis B vaccination; provision of take-home naloxone; fentanyl test strips (where available); safer use education (not injecting alone, not mixing substances, recognising overdose signs); and access to clean injecting equipment. Housing stability and social support are key determinants of recovery outcomes. Social prescribing, food banks, and support with benefits/housing are integral to holistic care. Screening for blood-borne viruses (HIV, hepatitis B and C) should be offered to all patients using intravenous drugs.
When to refer
Refer to Drug and Alcohol Action Teams (DAAT) or Substance Misuse and Recovery Services (SMARS) for structured community treatment including keyworking, counselling, OST, and recovery support groups including 12-step programmes (AA, NA) and SMART Recovery. Inpatient detox referral criteria: seizure risk, previous complicated withdrawal, Wernicke's risk, failed community detox, or severe dependence with no social support. Refer to hepatology if significant liver disease (cirrhosis, decompensated liver disease). Refer to dual diagnosis team or CMHT if comorbid severe mental illness. Refer to the pain team if chronic pain is driving opioid use disorder. Safeguarding referrals must be made if children are at risk.