Drugs of Abuse, Withdrawal, and Addiction Toxicology
This domain tests whether you can separate intoxication from withdrawal, predict the time course of each syndrome, and choose treatment that does not precipitate the event you are trying to prevent. Expect questions on withdrawal timelines and their danger, on medications for opioid and alcohol use disorder, and on adulterants that change the classic picture.
Intoxication patterns
Opioids cause miosis, respiratory depression and sedation; stimulants cause hypertension, tachycardia, diaphoresis and agitation with preserved orientation; alcohol and benzodiazepines cause disinhibition then depression; cannabis causes conjunctival injection, tachycardia and, at high dose, agitation or emesis; GHB produces abrupt deep coma with preserved reflexes and rapid recovery.
Withdrawal timelines and danger
- Alcohol: tremor and autonomic hyperactivity at 6–24 hours, seizures at 12–48 hours, delirium tremens at 48–96 hours. Alcohol and benzodiazepine withdrawal can kill.
- Benzodiazepines: onset depends on half-life - 1–4 days for short-acting agents, up to 1–2 weeks for long-acting - with protracted anxiety and perceptual symptoms.
- Opioids: lacrimation, rhinorrhoea, yawning, piloerection and diarrhoea peak at 36–72 hours. Miserable but not life-threatening.
- Stimulants: a crash of fatigue, depression and hypersomnia rather than a hyperadrenergic syndrome.
Treatment principles
Symptom-triggered benzodiazepines guided by a validated scale for alcohol withdrawal; thiamine before or with glucose to prevent Wernicke encephalopathy; methadone or buprenorphine for opioid use disorder, with buprenorphine started only when withdrawal is established to avoid precipitated withdrawal; naloxone distribution for overdose reversal. Adulterants matter: illicitly manufactured fentanyls increase overdose potency, and xylazine produces sedation unresponsive to naloxone.
Worked example. A 45-year-old presents 36 hours after his last drink with heart rate 120, blood pressure 160/95, tremor, diaphoresis and visual hallucinations, scoring 18 on the withdrawal scale. This is alcohol withdrawal with impending delirium tremens; he needs a benzodiazepine dosed to symptom scores, thiamine, glucose and electrolyte assessment, and a monitored bed. Beta-blockade alone would blunt the tachycardia used to titrate therapy and would not prevent seizures or delirium.
Traps that cost marks
- Using beta-blockers as monotherapy for alcohol withdrawal.
- Giving buprenorphine to a patient who is not yet in withdrawal.
- Assuming naloxone will reverse every overdose, including xylazine or stimulant toxicity.
- Treating a positive immunoassay as confirmation, or ignoring that opioid withdrawal is not lethal.