Medical School · Year 3 · Emergency Medicine · includes a quiz and discussion video

Seminar 07: Toxicological Emergencies

Year 3: Emergency Medicine Clerkship

Learning Objectives

By the end of this seminar, students will be able to:

1. Identify toxidromes and their underlying causes
2. Manage common overdoses and poisonings
3. Apply appropriate decontamination strategies
4. Utilize antidotes effectively
5. Recognize withdrawal syndromes
6. Access poison control resources

Seminar Outline

I. Approach to the Poisoned Patient

The initial approach to the poisoned patient prioritizes stabilization following the principles of airway, breathing, and circulation. Airway management takes precedence, with intubation indicated for patients unable to protect their airway due to altered mental status. Bedside glucose determination should be performed immediately, as hypoglycemia can mimic many toxidromes and is rapidly reversible. Empiric naloxone administration is appropriate when opioid overdose is suspected based on respiratory depression and miosis. Thiamine should precede or accompany glucose administration in patients at risk for Wernicke encephalopathy, particularly those with chronic alcoholism.

History gathering in the poisoned patient follows the SAMPLE mnemonic with additional toxicology-specific questions. The clinician should determine what substance was taken, the route of exposure, the estimated amount, and the time of ingestion. Intent is critical to establish, as intentional overdoses often involve multiple substances and require psychiatric evaluation. Patients may provide unreliable histories, making collateral information from family, friends, emergency medical services, and pill bottles essential. Prior overdose attempts increase the risk of subsequent attempts and help predict the potential severity of current ingestion.

Toxidrome recognition allows rapid diagnosis even when the specific ingested substance is unknown. The sympathomimetic toxidrome presents with tachycardia, hypertension, hyperthermia, diaphoresis, and mydriasis from agents such as cocaine, amphetamines, and synthetic cathinones. The anticholinergic toxidrome produces tachycardia, dry flushed skin, mydriasis, delirium, and urinary retention from antihistamines, tricyclic antidepressants, and atropine. The cholinergic toxidrome causes salivation, lacrimation, urination, defecation, gastrointestinal distress, and emesis (SLUDGE), along with bradycardia and bronchorrhea from organophosphates and nerve agents. The opioid toxidrome features respiratory depression, central nervous system depression, and miosis.

Poison Control Centers provide 24-hour toxicology expertise and should be contacted for all poisoning exposures. The national number (1-800-222-1222) connects callers with board-certified toxicologists who provide evidence-based management recommendations. Poison Control can assist with identification of unknown substances, determination of toxic doses, guidance on decontamination, antidote dosing, and disposition recommendations. Documentation of all recommendations from Poison Control is essential for the medical record and for following the recommended monitoring and treatment plan.

<image>Panel A: Algorithm for initial stabilization of the poisoned patient including ABCs, glucose, naloxone, and thiamine. Panel B: Comparison table of major toxidromes with vital signs, pupil findings, and skin characteristics. Panel C: Toxicology-specific history elements beyond SAMPLE. Panel D: Poison Control Center utilization flowchart with documentation requirements.</image>

II. Decontamination

Gastrointestinal decontamination aims to reduce absorption of ingested toxins, though the role of various methods has evolved significantly based on evidence. Activated charcoal remains the most useful decontamination method and works by adsorbing toxins in the gastrointestinal tract, preventing systemic absorption. The standard dose is 1 gram per kilogram of body weight, typically 50-100 grams in adults, and efficacy is greatest when administered within 1-2 hours of ingestion. Contraindications include altered mental status with unprotected airway due to aspiration risk, caustic ingestions where charcoal may obscure endoscopic evaluation, and substances not adsorbed by charcoal.

Certain substances are not effectively adsorbed by activated charcoal, requiring alternative approaches. Alcohols including ethanol, methanol, and ethylene glycol pass through charcoal without significant binding. Metals such as iron, lithium, and potassium are not adsorbed and require other management strategies. Hydrocarbons pose aspiration risk and are poorly bound by charcoal. Whole bowel irrigation with polyethylene glycol solution is indicated for body packers (drug couriers with ingested packets), sustained-release or enteric-coated medications, and metal ingestions.

Enhanced elimination techniques increase the clearance of already-absorbed toxins from the body. Multi-dose activated charcoal involves repeated doses that interrupt enterohepatic circulation and create a "gut dialysis" effect, useful for carbamazepine, phenobarbital, theophylline, and dapsone. Hemodialysis efficiently removes low-molecular-weight, water-soluble toxins with low protein binding and low volume of distribution, making it effective for methanol, ethylene glycol, lithium, salicylates, and valproic acid. Urine alkalinization with sodium bicarbonate increases renal elimination of weak acids such as salicylates and methotrexate by trapping ionized drug in the tubular lumen.

Surface decontamination protects both the patient and healthcare providers from continued absorption and secondary contamination. Skin exposures require removal of all clothing and thorough washing with copious water, as many toxins continue to absorb through intact skin. Eye exposures mandate immediate irrigation with normal saline or water for at least 15-20 minutes, with pH testing to confirm neutralization in caustic exposures. Organophosphate exposures require special attention to staff protection, including personal protective equipment and avoidance of cross-contamination. Importantly, induced vomiting with ipecac is no longer recommended in the emergency department due to limited efficacy and potential complications.

<image>Panel A: Activated charcoal indications, dosing, contraindications, and substances not adsorbed. Panel B: Whole bowel irrigation technique and indications. Panel C: Enhanced elimination methods comparing multi-dose charcoal, hemodialysis, and urine alkalinization. Panel D: Surface decontamination protocols for skin, eye, and organophosphate exposures.</image>

III. Acetaminophen Overdose

Acetaminophen toxicity follows a characteristic four-phase clinical progression that guides diagnosis and treatment. Phase I (0-24 hours) features nonspecific symptoms including nausea, vomiting, malaise, and diaphoresis, or patients may be entirely asymptomatic despite having ingested toxic amounts. Phase II (24-72 hours) sees the onset of hepatotoxicity with right upper quadrant pain and rising hepatic transaminases. Phase III (72-96 hours) represents peak hepatic injury with potential hepatic failure, coagulopathy, metabolic acidosis, and hepatic encephalopathy. Phase IV occurs after 96 hours and represents either recovery with hepatic regeneration or progression to death from fulminant hepatic failure.

Risk assessment relies on the Rumack-Matthew nomogram for acute single ingestions with known time of ingestion. A serum acetaminophen level should be drawn at 4 hours post-ingestion or as soon as possible thereafter, as levels before 4 hours cannot be plotted on the nomogram. The treatment line begins at 150 micrograms per milliliter at 4 hours and declines over time. Any level plotting above this line indicates treatment necessity. A toxic dose is generally considered to be greater than 150 mg/kg or 10 grams total in adults. Extended-release preparations, staggered ingestions, and unknown time of ingestion require modified approaches often involving empiric treatment.

N-acetylcysteine (NAC) serves as the antidote for acetaminophen toxicity by replenishing glutathione stores and providing alternative pathways for detoxification of the toxic metabolite NAPQI. The 21-hour intravenous protocol administers 150 mg/kg over 1 hour as a loading dose, followed by 50 mg/kg over 4 hours, and then 100 mg/kg over 16 hours. Oral NAC is an alternative, given as 140 mg/kg loading dose followed by 70 mg/kg every 4 hours for 17 additional doses. Efficacy is greatest when treatment begins within 8 hours of ingestion, but NAC provides benefit even in delayed presentations with established hepatotoxicity. Anaphylactoid reactions can occur with intravenous administration but typically respond to slowing the infusion and antihistamine administration.

Disposition depends on serum acetaminophen level, timing of NAC initiation, and clinical status. Patients with levels below the treatment line who are asymptomatic can be observed and discharged with psychiatric evaluation if the ingestion was intentional. Those receiving NAC should complete the entire protocol, with serial liver function tests and coagulation studies to monitor for hepatotoxicity. Patients developing hepatic failure require intensive care monitoring and evaluation for liver transplantation. King's College criteria help identify patients who may benefit from transplant, including arterial pH less than 7.3 after resuscitation or the combination of grade III/IV encephalopathy, prothrombin time greater than 100 seconds, and creatinine greater than 3.4 mg/dL.

<image>Panel A: Four phases of acetaminophen toxicity with timeline and clinical features. Panel B: Rumack-Matthew nomogram with treatment line and interpretation. Panel C: N-acetylcysteine protocols comparing intravenous and oral regimens. Panel D: Disposition algorithm including criteria for liver transplant evaluation.</image>

IV. Salicylate Toxicity

Salicylate toxicity presents with a spectrum of severity ranging from mild symptoms to life-threatening poisoning. Mild toxicity produces nausea, vomiting, and tinnitus, which represents cochlear toxicity from salicylates. Moderate toxicity adds hyperpnea from direct respiratory center stimulation, diaphoresis, and fever from uncoupled oxidative phosphorylation. Severe toxicity manifests as altered mental status, pulmonary edema, seizures, and cardiovascular collapse. The hallmark acid-base disturbance is the combination of respiratory alkalosis from central stimulation of ventilation and metabolic acidosis from accumulated organic acids and salicylic acid itself.

The pathophysiology of salicylate toxicity involves multiple mechanisms that explain the clinical findings. Direct stimulation of the respiratory center in the medulla produces primary respiratory alkalosis with tachypnea and hypocapnia. Uncoupling of oxidative phosphorylation in mitochondria increases metabolic rate, generating heat and consuming oxygen while producing organic acids. This metabolic acidosis eventually overcomes the respiratory compensation. Cerebral edema develops in severe cases through incompletely understood mechanisms. Understanding that salicylate distribution into tissues, particularly the brain, increases dramatically with acidemia is critical, as even small decreases in pH dramatically increase central nervous system toxicity.

Treatment of salicylate toxicity focuses on preventing continued absorption, enhancing elimination, and avoiding factors that worsen toxicity. Activated charcoal is beneficial even with delayed presentation due to potential for delayed gastric emptying and formation of bezoars. Urine alkalinization with sodium bicarbonate infusion creates an alkaline urine (target pH 7.5-8.0) that traps ionized salicylate in the renal tubules, dramatically increasing urinary excretion. Potassium replacement is essential, as hypokalemia prevents effective urine alkalinization. Glucose supplementation is recommended even with normal serum glucose because cerebrospinal fluid glucose may be depleted.

Intubation should be avoided if possible in salicylate toxicity because maintaining the degree of hyperventilation these patients achieve spontaneously is extremely difficult with mechanical ventilation. Any period of hypoventilation during intubation or sedation allows respiratory acidosis that dramatically increases salicylate penetration into the central nervous system, potentially precipitating rapid deterioration. Hemodialysis provides definitive treatment for severe toxicity and is indicated for serum levels exceeding 100 mg/dL, altered mental status, acute kidney injury, pulmonary edema, or failure to improve with supportive care. Serial salicylate levels should be monitored until clearly declining, as delayed absorption can cause secondary peaks.

<image>Panel A: Clinical presentation spectrum from mild to severe salicylate toxicity. Panel B: Pathophysiology diagram showing respiratory alkalosis, metabolic acidosis, and tissue distribution. Panel C: Urine alkalinization protocol with sodium bicarbonate dosing and monitoring targets. Panel D: Indications for hemodialysis and pitfalls of intubation in salicylate poisoning.</image>

V. Opioid Overdose

Recognition of opioid overdose relies on the classic triad of respiratory depression, central nervous system depression, and miosis. Respiratory depression represents the life-threatening component, with respiratory rates below 12 breaths per minute, shallow breathing, or apnea. Pupils are characteristically pinpoint, though this finding may be absent with certain synthetic opioids or co-ingestions. Hypoxia from respiratory depression leads to secondary cardiovascular effects including bradycardia and hypotension. Needle marks, drug paraphernalia, or known history of opioid use support the diagnosis but are not required for treatment.

Naloxone is a competitive opioid receptor antagonist that rapidly reverses opioid effects. Intravenous administration provides the fastest onset at 1-2 minutes, with typical doses of 0.4-2 mg. Intramuscular and subcutaneous routes have onset of 2-5 minutes, while intranasal naloxone (4 mg) provides a needle-free option with onset of 3-5 minutes. Doses may be repeated every 2-3 minutes as needed to restore adequate ventilation. The duration of naloxone (30-90 minutes) is shorter than most opioids, necessitating continued observation and potentially repeat dosing or continuous infusion for long-acting opioid ingestions.

Management considerations include titrating naloxone to respiratory effort rather than complete arousal to avoid precipitating withdrawal in opioid-dependent patients. Starting with lower doses (0.04-0.4 mg) in known chronic opioid users prevents acute withdrawal, which although not life-threatening is extremely unpleasant and may cause the patient to leave against medical advice. High-potency synthetic opioids like fentanyl may require larger cumulative naloxone doses. Long-acting opioids such as methadone, extended-release formulations, and buprenorphine require prolonged observation periods and may need naloxone infusion, typically at two-thirds of the effective bolus dose per hour.

Disposition depends on the clinical response and the suspected opioid. Patients who respond to naloxone and remain stable should be observed for at least 4-6 hours after the last naloxone dose. Long-acting opioid ingestions require admission for extended monitoring given the risk of recurrent toxicity after naloxone wears off. Intentional overdoses require psychiatric evaluation once medically stable. Harm reduction strategies including naloxone prescriptions for take-home use, information about treatment resources, and non-judgmental education about overdose prevention should be offered to all patients with opioid use disorder.

<image>Panel A: Opioid toxidrome with classic triad and secondary findings. Panel B: Naloxone administration routes, doses, and onset times. Panel C: Titration strategy comparing opioid-naive versus opioid-dependent patients. Panel D: Disposition algorithm based on opioid type and clinical response.</image>

VI. Sympathomimetic Toxicity

Sympathomimetic substances stimulate the sympathetic nervous system through various mechanisms, producing a characteristic toxidrome. Illicit substances include cocaine, which blocks catecholamine reuptake, and methamphetamine, which causes catecholamine release from nerve terminals. MDMA (ecstasy) combines sympathomimetic effects with serotonergic activity. Prescription amphetamines used for attention deficit disorder can cause toxicity in overdose. Over-the-counter sympathomimetics include pseudoephedrine and phenylephrine. Synthetic cathinones ("bath salts") represent an emerging class with particularly dangerous and unpredictable effects.

The clinical presentation reflects excessive sympathetic activation affecting multiple organ systems. Cardiovascular manifestations include tachycardia, hypertension, arrhythmias, and in severe cases myocardial ischemia or infarction from vasospasm and increased myocardial oxygen demand. Central nervous system effects range from agitation and anxiety to seizures, intracranial hemorrhage, and severe hyperthermia. Psychiatric symptoms include paranoia, psychosis, and violent behavior. Serious complications include rhabdomyolysis from muscle hyperactivity, disseminated intravascular coagulation, and multi-organ failure in severe hyperthermia.

Management of sympathomimetic toxicity centers on benzodiazepines as first-line therapy for most manifestations. Benzodiazepines address agitation, reduce seizure risk, lower blood pressure and heart rate through central sympatholytic effects, and decrease hyperthermia. Aggressive cooling is essential for temperatures exceeding 40 degrees Celsius (104 degrees Fahrenheit), using evaporative cooling, ice packs to groin and axillae, and cold intravenous fluids. Beta-blockers should be avoided in cocaine toxicity due to the risk of unopposed alpha-adrenergic stimulation causing paradoxical hypertension and coronary vasoconstriction. Persistent hypertension after adequate benzodiazepine dosing may require nitrates or nicardipine.

Cocaine produces specific complications requiring tailored management. Chest pain in cocaine users should prompt consideration of acute coronary syndrome, though the differential includes musculoskeletal pain, anxiety, and pulmonary etiologies. Treatment includes benzodiazepines for pain and anxiety, aspirin unless contraindicated, and nitrates for coronary vasospasm. ST-elevation myocardial infarction should prompt primary percutaneous intervention rather than fibrinolytics when available due to the increased bleeding risk. The traditional concern about labetalol's beta-blockade in cocaine toxicity has led many to prefer pure alpha-blockers or calcium channel blockers for refractory hypertension.

<image>Panel A: Classification of sympathomimetic substances by mechanism and source. Panel B: Multi-system manifestations of sympathomimetic toxicity. Panel C: Benzodiazepine-centered management approach with escalation options. Panel D: Cocaine-specific complications including chest pain evaluation and treatment algorithm.</image>

VII. Sedative-Hypnotic Overdose

Benzodiazepine overdose in isolation rarely causes life-threatening toxicity, but co-ingestion with other central nervous system depressants dramatically increases risk. Patients present with sedation ranging from drowsiness to obtundation, ataxia, slurred speech, and in severe cases respiratory depression. Physical examination typically reveals normal vital signs and normal pupil size, distinguishing benzodiazepines from opioids. Treatment is primarily supportive, focusing on airway protection and ventilatory support as needed. Activated charcoal may be considered if the patient presents early with a protected airway.

Flumazenil is a competitive benzodiazepine receptor antagonist that can reverse sedation but carries significant risks that limit its use. Administration can precipitate seizures in patients with chronic benzodiazepine use who have developed physiologic dependence, as well as in patients who have co-ingested seizure-threshold-lowering drugs such as tricyclic antidepressants. Additionally, flumazenil may precipitate severe withdrawal symptoms. Appropriate use is primarily limited to reversal of procedural sedation in patients without seizure risk factors or known chronic benzodiazepine use. In most overdose situations, supportive care is safer than flumazenil.

Barbiturate overdose produces more severe toxicity than benzodiazepines, including profound central nervous system depression, respiratory failure, and cardiovascular collapse with hypotension. This increased danger relates to barbiturates' direct activation of GABA receptors rather than benzodiazepines' modulatory effects. Treatment requires aggressive supportive care including mechanical ventilation and vasopressor support for hypotension. Enhanced elimination with multi-dose activated charcoal and urine alkalinization is effective for long-acting barbiturates such as phenobarbital. There is no specific antidote for barbiturate toxicity.

Gamma-hydroxybutyrate (GHB) overdose has distinctive features including rapid onset and relatively rapid resolution of symptoms. Patients present with profound central nervous system depression, often requiring intubation, but typically recover within several hours as the drug is rapidly metabolized. Bradycardia may accompany the sedation. GHB withdrawal can be severe and resembles alcohol withdrawal, with anxiety, tremor, tachycardia, and potential for seizures and delirium. Treatment of GHB withdrawal involves high-dose benzodiazepines, often requiring much higher doses than typical alcohol withdrawal. Barbiturates or propofol may be needed for refractory cases.

<image>Panel A: Benzodiazepine toxicity presentation and differentiation from opioid overdose. Panel B: Flumazenil indications, contraindications, and risks. Panel C: Barbiturate overdose severity comparison with benzodiazepines and management approach. Panel D: GHB unique features including rapid onset/offset and withdrawal syndrome.</image>

VIII. Anticholinergic and Cholinergic Toxicity

The anticholinergic syndrome results from muscarinic receptor blockade and produces a characteristic clinical picture memorable through classic mnemonics. "Mad as a hatter" describes the delirium, agitation, and sometimes hallucinations caused by central antimuscarinic effects. "Blind as a bat" refers to mydriasis and cycloplegia producing blurred vision. "Red as a beet" describes the flushed skin from cutaneous vasodilation in the absence of sweating. "Hot as a hare" indicates hyperthermia from inability to sweat and dissipate heat. "Dry as a bone" captures the dry skin, dry mucous membranes, and urinary retention from blocked secretory and smooth muscle function.

Causes of anticholinergic toxicity span multiple drug classes frequently encountered in the emergency department. First-generation antihistamines such as diphenhydramine commonly cause toxicity, particularly in intentional overdose. Tricyclic antidepressants produce anticholinergic effects in addition to their more dangerous sodium channel blockade and alpha-adrenergic antagonism. Atropine and scopolamine produce pure anticholinergic toxicity. Antipsychotic medications, particularly low-potency typical antipsychotics, have significant anticholinergic activity. Jimson weed (Datura) and other belladonna alkaloid-containing plants cause toxicity when ingested for recreational purposes.

Treatment of anticholinergic toxicity is primarily supportive in most cases. External cooling addresses hyperthermia, which can be severe in the absence of sweating. Benzodiazepines control agitation and reduce seizure risk. Physostigmine, a cholinesterase inhibitor that crosses the blood-brain barrier, can dramatically reverse both peripheral and central anticholinergic effects. The dose is 0.5-2 mg administered slowly intravenously over 5 minutes. However, physostigmine is contraindicated when the QRS complex is widened (suggesting tricyclic antidepressant toxicity) due to the risk of asystole and when there is a history of seizures. Use should be limited to pure anticholinergic toxicity causing significant morbidity such as severe hyperthermia or agitated delirium uncontrolled by benzodiazepines.

The cholinergic syndrome results from excessive stimulation of muscarinic and nicotinic receptors and is classically caused by organophosphate or carbamate poisoning. The SLUDGE mnemonic captures muscarinic effects: Salivation, Lacrimation, Urination, Defecation, Gastrointestinal distress, and Emesis. The "BBB" addition reminds of Bradycardia, Bronchorrhea, and Bronchospasm, which are life-threatening. Nicotinic effects at the neuromuscular junction can cause muscle fasciculations followed by weakness and paralysis. Treatment requires atropine titrated to dry pulmonary secretions, often requiring massive doses in severe organophosphate poisoning. Pralidoxime (2-PAM) reactivates acetylcholinesterase and should be given early before "aging" of the enzyme-toxin complex occurs. Decontamination is critical, and healthcare workers must protect themselves from secondary exposure.

<image>Panel A: Anticholinergic syndrome mnemonics with clinical findings and common causes. Panel B: Physostigmine indications, contraindications, dosing, and monitoring. Panel C: Cholinergic toxidrome with SLUDGE and BBB mnemonics. Panel D: Organophosphate management including atropine titration, pralidoxime dosing, and decontamination.</image>

IX. Toxic Alcohols

Methanol poisoning occurs from ingestion of windshield washer fluid, fuel additives, or improperly distilled spirits (moonshine). The parent compound methanol is relatively nontoxic, but metabolism by alcohol dehydrogenase produces formaldehyde, which is further oxidized to formic acid, the primary toxic metabolite. Formic acid causes metabolic acidosis and has specific toxicity to the optic nerve and basal ganglia. Patients may present initially with inebriation followed hours later by visual disturbances ranging from blurred vision to complete blindness, headache, nausea, and altered mental status. Laboratory findings include elevated osmolal gap early (from the parent alcohol) and elevated anion gap later (from the acid metabolite).

Ethylene glycol, the primary component of antifreeze, follows a similar metabolic pathway with different toxic products. Metabolism produces glycolic acid, which causes severe metabolic acidosis, and oxalic acid, which precipitates as calcium oxalate crystals in renal tubules causing acute kidney injury. The classic clinical progression involves initial inebriation, followed by cardiopulmonary effects from acidosis, and finally renal failure from crystal deposition. Calcium oxalate crystals may be visible on urinalysis, appearing as envelope-shaped or needle-shaped crystals. The historical teaching that urine fluoresces under Wood's lamp due to fluorescein additive in antifreeze is unreliable and should not be used to exclude the diagnosis.

Treatment of toxic alcohol poisoning focuses on blocking metabolism to prevent formation of toxic metabolites. Fomepizole (4-methylpyrazole) is a potent alcohol dehydrogenase inhibitor given as a 15 mg/kg loading dose followed by maintenance dosing every 12 hours. Ethanol serves as an alternative substrate for alcohol dehydrogenase with higher binding affinity than methanol or ethylene glycol, effectively blocking their metabolism, but requires careful titration to maintain therapeutic blood levels and causes inebriation. Sodium bicarbonate corrects metabolic acidosis and improves the ionization state of organic acids, reducing tissue penetration. Cofactor supplementation with thiamine and pyridoxine may enhance metabolism of toxic intermediates through alternative pathways.

Hemodialysis provides definitive treatment by removing both the parent alcohol and toxic metabolites while correcting acidosis. Indications for dialysis include severe metabolic acidosis (pH less than 7.25-7.30), renal failure in ethylene glycol poisoning, visual symptoms in methanol poisoning, serum toxic alcohol level exceeding 50 mg/dL, and clinical deterioration despite antidotal therapy. Without fomepizole or dialysis, methanol or ethylene glycol poisoning carries high mortality. Even with treatment, permanent sequelae including blindness from methanol and chronic kidney disease from ethylene glycol may occur if treatment is delayed.

<image>Panel A: Methanol metabolism pathway showing formaldehyde and formic acid production with ocular toxicity mechanism. Panel B: Ethylene glycol metabolism showing oxalic acid production and calcium oxalate crystal nephropathy. Panel C: Comparison of fomepizole versus ethanol as alcohol dehydrogenase inhibitors. Panel D: Hemodialysis indications and outcomes in toxic alcohol poisoning.</image>

X. Alcohol Withdrawal

Alcohol withdrawal represents a spectrum of syndromes occurring when chronic heavy drinkers reduce or cease alcohol consumption. Minor withdrawal begins 6-24 hours after the last drink and manifests as tremor, anxiety, insomnia, tachycardia, and hypertension. Withdrawal seizures, typically generalized tonic-clonic, occur in the 12-48 hour window and may be the presenting symptom without preceding minor symptoms. Alcoholic hallucinosis involves visual, auditory, or tactile hallucinations (classically formication, the sensation of insects crawling on the skin) occurring at 12-48 hours but with preserved clear sensorium distinguishing it from delirium tremens. Delirium tremens, the most severe manifestation, develops at 48-96 hours and features profound confusion, agitation, autonomic instability with fever, tachycardia, and diaphoresis.

Risk assessment helps predict which patients will develop significant withdrawal and guides treatment intensity. The Prediction of Alcohol Withdrawal Severity Scale (PAWSS) helps identify patients at risk before withdrawal develops. The Clinical Institute Withdrawal Assessment for Alcohol-Revised (CIWA-Ar) scores current withdrawal severity based on symptoms including nausea, tremor, sweating, anxiety, agitation, tactile disturbances, auditory disturbances, visual disturbances, headache, and orientation. Historical risk factors for severe withdrawal include prior withdrawal seizures, prior delirium tremens, heavy daily consumption, prolonged drinking binges, and concurrent medical illness.

Treatment of alcohol withdrawal relies primarily on benzodiazepines, which have cross-tolerance with alcohol through their shared mechanism at GABA-A receptors. Symptom-triggered dosing guided by CIWA-Ar scores results in lower total benzodiazepine doses and shorter treatment courses compared to fixed-schedule protocols. However, fixed-schedule dosing is appropriate for high-risk patients, those with prior severe withdrawal, and those unable to participate in frequent assessments. Long-acting benzodiazepines such as diazepam or chlordiazepoxide provide smoother coverage, while lorazepam is preferred in patients with hepatic dysfunction due to its lack of active metabolites. Adjunctive treatments include thiamine to prevent Wernicke encephalopathy, folate, and multivitamins.

Refractory alcohol withdrawal uncontrolled by benzodiazepines requires escalation to additional agents and intensive care monitoring. Phenobarbital provides additional GABA-ergic activity through direct receptor activation rather than the modulatory effects of benzodiazepines, with typical loading doses of 10-15 mg/kg. Propofol effectively controls severe withdrawal but requires intubation and mechanical ventilation. Dexmedetomidine, a centrally acting alpha-2 agonist, serves as an adjunct to benzodiazepines, reducing sympathetic outflow and providing sedation without respiratory depression. Antipsychotics should generally be avoided or used cautiously because they lower seizure threshold. Patients with delirium tremens or refractory withdrawal require ICU admission for close monitoring and management of the high mortality associated with these conditions.

<image>Panel A: Timeline and spectrum of alcohol withdrawal from minor withdrawal through delirium tremens. Panel B: CIWA-Ar scoring components and symptom-triggered treatment protocol. Panel C: Comparison of benzodiazepine agents with properties and dosing. Panel D: Refractory withdrawal management including phenobarbital loading and ICU escalation.</image>

Summary

• Toxidromes: sympathomimetic (tachycardia, hypertension, diaphoresis, mydriasis), anticholinergic (dry, flushed, mydriasis, delirium), cholinergic (SLUDGE, bradycardia, bronchorrhea), opioid (miosis, respiratory depression, CNS depression)
• Activated charcoal: most effective within 1-2 hours; not useful for alcohols, metals, or hydrocarbons
• Acetaminophen: four-phase toxicity; NAC is the antidote; Rumack-Matthew nomogram guides treatment; best outcomes if NAC started within 8 hours
• Salicylates: respiratory alkalosis with metabolic acidosis; urine alkalinization; hemodialysis for severe toxicity; avoid intubation if possible
• Opioid overdose: naloxone 0.4-2 mg IV/IM/IN; titrate to respiratory effort; observe for recurrent toxicity with long-acting opioids
• Sympathomimetics: benzodiazepines are first-line for agitation, hypertension, and seizures; avoid beta-blockers in cocaine toxicity
• Organophosphates: atropine titrated to dry secretions plus pralidoxime; decontamination with staff protection
• Toxic alcohols: fomepizole or ethanol blocks metabolism; hemodialysis for severe acidosis, visual changes, or high levels
• Alcohol withdrawal: benzodiazepines are mainstay; CIWA-Ar guided or fixed-schedule dosing; phenobarbital for refractory cases; thiamine always

Key Terms

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