Substance Use Disorders
Definitions
Distinguish use, harmful use/abuse, dependence (compulsion, loss of control, withdrawal, tolerance, salience), and withdrawal. DSM-5 combines abuse and dependence into a single substance use disorder with severity graded by number of criteria (mild 2–3, moderate 4–5, severe ≥6).
Withdrawal syndromes - high-yield
- Alcohol: tremor, sweating, anxiety, seizures, delirium tremens (24–72h, autonomic instability, mortality without treatment). Treat with benzodiazepines (chlordiazepoxide/lorazepam), thiamine before glucose, and manage Wernicke's encephalopathy with parenteral thiamine.
- Opioid: yawning, rhinorrhoea, piloerection, diarrhoea, mydriasis - distressing but rarely fatal; treat with substitution/tapering.
- Benzodiazepine: anxiety, insomnia, seizures; taper slowly.
Intoxication and harm reduction
Know opioid overdose (pinpoint pupils, respiratory depression) → naloxone; and that flumazenil is avoided in mixed overdose due to seizure risk.
Traps
- Giving glucose before thiamine in an at-risk patient (precipitates Wernicke's).
- Missing dual diagnosis - comorbid psychiatric illness is the rule, not the exception.
- Assuming withdrawal is the main danger in every substance; alcohol and benzodiazepine withdrawal are the life-threatening ones.
Rule of thumb
In any confused, agitated patient in hospital, think substance withdrawal or intoxication before psychiatric diagnosis, and always check glucose, thiamine, and a toxicology screen.