Which substance withdrawals can be fatal?

Alcohol and the sedative-hypnotics (benzodiazepines and barbiturates) are the withdrawals that can kill, through seizures and delirium tremens with autonomic instability. Opioid and stimulant withdrawal are very uncomfortable but rarely lethal in an otherwise healthy adult. Alcohol and sedative withdrawal are treated with a benzodiazepine taper.

Why is thiamine given before glucose in an alcohol-dependent patient?

Chronic heavy drinking depletes thiamine. Giving glucose first consumes the remaining thiamine and can precipitate Wernicke encephalopathy: confusion, ophthalmoplegia, and ataxia. Wernicke is reversible if treated early, but untreated it can progress to permanent Korsakoff amnesia. So thiamine is given before or with glucose.

Why avoid pure beta-blockers in cocaine-associated chest pain?

Cocaine drives both alpha and beta adrenergic stimulation. Blocking only beta receptors leaves alpha-mediated vasoconstriction unopposed, which can worsen coronary spasm and hypertension. The first-line treatment is a benzodiazepine to reduce sympathetic tone, along with aspirin and nitrates.

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Psychiatry · Addiction Medicine

Substance Intoxication and Withdrawal

One drug presses the brake, another hits the gas. Learn the mirror rule, the only two withdrawals that kill, the antidotes, and why thiamine always goes in before glucose.

The Setup

Brake Pedal, Gas Pedal

Every drug pushes the brain one direction. Name the direction and you already know what intoxication and withdrawal look like, and which withdrawals can kill.

A 52-year-old man is on hospital day 2 after an elective hip operation. He becomes tremulous and drenched in sweat. His blood pressure is 172/104, heart rate 124, temperature 100.9 F. He then has a generalized seizure and afterward is confused and swatting at bugs he sees on the wall. Records note he drinks heavily every day.

Which withdrawal is this, and how dangerous is it?

One rule runs the whole topic: intoxication and withdrawal are mirror images. A drug that presses the brake (a CNS depressant: alcohol, benzodiazepines, barbiturates, opioids) makes you sedated and slow while it is on board, and the withdrawal is the rebound, an overexcited brain. A drug that hits the gas (a stimulant: cocaine, amphetamines) makes you wired and fast while on board, and withdrawal is the crash. Name the direction the drug pushes and you already know what intoxication and withdrawal look like.

Now the line that saves lives. Most withdrawals are miserable but survivable. Only alcohol and the sedative-hypnotics (benzodiazepines and barbiturates) reliably kill through withdrawal, because pulling a chronic brake off an adapted brain causes seizures and autonomic collapse. Opioid withdrawal feels like the worst flu of your life but does not kill an otherwise healthy adult. clinical medicine lean on that asymmetry over and over.

Sort every drug into a lane first. Flip each card.

CNS depressantsTap to flip

Brake pedalAlcohol, benzodiazepines, barbiturates, opioids. On board: sedation, slow breathing, low energy. Coming off: rebound activation. For alcohol and sedatives that rebound can become seizures and delirium.

StimulantsTap to flip

Gas pedalCocaine and amphetamines. On board: wired, dilated pupils, racing heart, paranoia. Coming off: a crash with sleep, hunger, low mood, and craving. Uncomfortable, not deadly.

The lethal withdrawalsTap to flip

Memorize this pairAlcohol and the sedative-hypnotics are the withdrawals that can kill. Both are treated by replacing the brake with a benzodiazepine and tapering it down slowly.

At the Bedside

Reading the Syndromes

The pupils and the breathing rate split depressants from stimulants in seconds. Learn the six pictures and their antidotes.

Read the pupils and the breathing first. The eyes and the respiratory rate split the depressants from the stimulants faster than any history. Tap each syndrome.

Opioids

Tap to reveal

Pinpoint pupils (miosis), slow shallow breathing, deep sedation, and constipation. Respiratory depression is what kills. The antidote is naloxone, which reverses it within minutes.

Stimulants

Tap to reveal

Big pupils (mydriasis), fast heart, high blood pressure, high temperature, agitation, and paranoia. Some feel bugs crawling on the skin (formication). Cocaine adds chest pain from coronary spasm.

Sedative-hypnotics

Tap to reveal

Slurred speech, unsteady gait (ataxia), drowsiness, and nystagmus, basically looking drunk. Alcohol, benzodiazepines, and barbiturates share this picture. The benzodiazepine antidote is flumazenil, used with great caution.

PCP

Tap to reveal

Violent agitation, numbness to pain, high blood pressure, and the giveaway: nystagmus in every direction (vertical, horizontal, and rotary). Place the patient in a calm, low-stimulation room and sedate with a benzodiazepine.

Hallucinogens (LSD)

Tap to reveal

Vivid visual changes and dilated pupils, but the person usually knows the experience is drug-induced. There is no dangerous physical withdrawal. Manage a bad trip with reassurance and a quiet room.

Cannabis

Tap to reveal

Red (injected) conjunctivae, dry mouth, increased appetite, a slowed sense of time, and a fast heart. Withdrawal is mild: irritability, poor sleep, and reduced appetite.

From the AttendingPinpoint pupils plus a respiratory rate of 6 is an opioid until proven otherwise, and your hand should already be reaching for naloxone. Blown pupils plus a heart rate of 140 and a soaring blood pressure is a stimulant. The eyes and the breathing rate are your two fastest discriminators at the bedside.

Confirming It

Which Withdrawal Kills

The dangerous decisions all come down to recognizing the lethal withdrawals and giving the right replacement.

Three forks decide the dangerous calls. Work each one before you reveal it.

Which withdrawal is the one most likely to kill an otherwise healthy adult?

Alcohol and the sedative-hypnotics. Removing a chronic brake leaves the brain dangerously overexcited, which drives seizures and delirium tremens with autonomic instability. Opioid withdrawal is brutal but rarely lethal. If a withdrawal can kill, it is almost always alcohol or a sedative-hypnotic.

A man is 60 hours past his last drink. He is confused, febrile, has a heart rate of 130, and is hallucinating. Which stage is this?

Delirium tremens. The hallmark is the late window (48 to 96 hours) plus a clouded sensorium and an autonomic storm: fever, tachycardia, hypertension, and sweating. It carries real mortality. Confusion plus autonomic instability days after the last drink equals delirium tremens, an emergency.

What is the cornerstone treatment for alcohol withdrawal?

A benzodiazepine. It substitutes for the missing brake and is titrated to a withdrawal scale. A beta-blocker only masks the heart rate and blood pressure while the brain keeps marching toward seizures. Treat alcohol and sedative withdrawal with a benzodiazepine taper, not a beta-blocker.

Line the three big withdrawals up side by side.

Withdrawal	Pupils and key signs	Deadly?	Treatment
Alcohol / sedative	Tremor, sweating, seizures, delirium tremens	Yes	Benzodiazepine taper; thiamine
Opioid	Big pupils, yawning, runny nose, diarrhea, cramps, gooseflesh	No (rarely)	Buprenorphine or methadone; clonidine for autonomics
Stimulant	The crash: sleep, hunger, low mood, vivid dreams, craving	No	Supportive care; watch for suicidality

The Plan

Antidotes and Pearls

Match the poison to the antidote, then lock in the two pearls that decide questions: thiamine before glucose, and no pure beta-blockers in cocaine toxicity.

Match the poison to the antidote. A handful of these are tested constantly.

Problem	Give
Opioid overdose (pinpoint pupils, low respiratory rate)	Naloxone
Benzodiazepine overdose	Flumazenil (avoid if chronic use or unknown co-ingestion; it can trigger seizures)
Alcohol or sedative withdrawal	Benzodiazepine taper, guided by a withdrawal scale
Acetaminophen overdose	N-acetylcysteine
Methanol or ethylene glycol	Fomepizole
Opioid use disorder, long term	Methadone or buprenorphine; naltrexone after detox

Two more pearls that decide a question. In a heavy drinker, the brain is starved of thiamine (vitamin B1). Pouring in glucose without thiamine first can tip them into Wernicke encephalopathy: confusion, eye-movement paralysis (ophthalmoplegia), and a wobbly gait (ataxia). If it is missed it hardens into Korsakoff, with permanent memory loss and made-up stories to fill the gaps (confabulation).

From the AttendingIn any malnourished or alcohol-dependent patient, thiamine goes in before glucose, every time. Wernicke is reversible if you treat it fast. Korsakoff is not. Spend the dollar on thiamine and you may save the memory.

Board TrapA cocaine user with chest pain gets a benzodiazepine first to calm the sympathetic surge, plus aspirin and nitrates. Do not reach for a pure beta-blocker: blocking beta while alpha runs wild leaves unopposed alpha vasoconstriction that can worsen coronary spasm and blood pressure. And flumazenil in a chronic benzodiazepine user can precipitate a withdrawal seizure, so it is rarely the right answer.

Prove It

Board Walkthrough

Original clinical vignettes, 5 dealt per round, answer choices shuffled, never repeating within a round. Tap a wrong answer first to see why it almost works, then read the glowing clues.

Medically reviewed by Fatima Ali, DO and Kaitlyn Cocuzzo, MD · Last reviewed June 2026

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