Substance Use Disorders and Addictive Behaviour
What the exam tests
Substance questions test intoxication, withdrawal, dependence, harm and treatment. You must know timelines, dangerous withdrawals and the difference between tolerance and withdrawal.
Core rules
- Dependence syndrome includes impaired control, salience, tolerance, withdrawal, continued use despite harm and narrowing of repertoire.
- Alcohol withdrawal begins hours after the last drink, with tremor, sweating, anxiety and nausea; seizures occur around 6-48 hours and delirium tremens at 48-96 hours.
- Opioid withdrawal is distressing but rarely fatal; opioid overdose causes pinpoint pupils, respiratory depression and responds to naloxone.
- Benzodiazepine withdrawal can cause seizures and psychosis; taper gradually, never stop abruptly.
- Brief interventions and motivational interviewing suit harmful use; opioid substitution and psychosocial treatment suit dependence.
Worked example
A man who drinks daily stops and 12 hours later has tremor, sweating, tachycardia and visual hallucinations. This is alcohol withdrawal with perceptual disturbances. The reasoning is the timeline and autonomic hyperactivity; he is at risk of seizures and delirium tremens. Treat with a benzodiazepine, give thiamine before glucose, correct fluids and electrolytes, and monitor.
Traps that cost marks
Do not miss Wernicke encephalopathy: confusion, ataxia and ophthalmoplegia require urgent thiamine. Do not treat alcohol withdrawal with antipsychotics alone. Do not assume withdrawal means dependence in every patient. Do not forget pregnancy, liver disease and polydrug use.