Acetaminophen toxicityMANAGEMENT

TOXICOLOGIC PRESENTATIONS · 12 SECTIONS

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467 items

☷ Legend

01Approach to the Critical Patient/attcp47

Immediate priorities

›First minute priorities

›Airway risk

›GCS decline

›Recurrent vomiting

›Aspiration risk

›Breathing

›Hypoventilation from coingestants

›Pulse oximetry target normal range

›Circulation

›Hypotension

›Shock state

›IV access x2

›Rapid bedside threats

›Altered mental status with severe metabolic acidosis

›Hypoglycemia

›Early antidote decision

›N-acetylcysteine time to start

›Start immediately if time unknown and acetaminophen detectable

›Start immediately if delayed presentation and hepatotoxicity suspected

›Do not delay for level if ingestion >8 hours possible

›Early decontamination decision

›Activated charcoal window

›Most benefit within 2 hours

›Consider up to 4 hours for massive ingestion

›Consider up to 4 hours for extended release

›Monitoring and escalation

›Telemetry

›Coingestant concern

›Significant electrolyte abnormalities

›ICU triggers

›Encephalopathy

›INR rising with metabolic acidosis

›Lactate elevation despite resuscitation

›Refractory hypoglycemia

Key concepts

›Core framework

›Exposure pattern

›Acute single ingestion with known time

›Acute ingestion with unknown time

›Repeated supratherapeutic ingestion

›Sustained release ingestion

›Two parallel tracks

›Serum acetaminophen interpretation pathway

›Liver injury and failure pathway

›High risk modifiers

›Chronic alcohol use

›Malnutrition

›Enzyme inducing drugs

02History/hx61

Exposure characterization

›Exposure details

›Time of ingestion

›Single time point

›Staggered ingestion timeline

›Time uncertainty

›Product formulation

›Immediate release

›Extended release

›Combination products

›Dose estimate

›mg/kg estimate

›Total grams estimate

›Coingestions

›Opioids

›Anticholinergics

›Salicylates

›Ethanol

›Intent and context

›Self-harm intent

›Psychiatric history

›Current stressors

›Accidental overdose

›Multiple acetaminophen containing products

›Dosing interval misunderstanding

›Risk factors for hepatotoxicity

›Malnutrition or fasting

›Chronic alcohol use

›Chronic liver disease

›Enzyme inducers

›Carbamazepine

›Phenytoin

›Phenobarbital

›Rifampin

›Symptom timeline

›Early phase

›Nausea

›Vomiting

›Diaphoresis

›Malaise

›Delayed phase

›RUQ pain

›Jaundice

›Confusion

›Oliguria

Classic and atypical presentations

›Expected clinical course

›0 to 24 hours

›GI symptoms possible

›Normal exam common

›24 to 72 hours

›RUQ tenderness possible

›AST and ALT rising

›72 to 96 hours

›Peak hepatotoxicity

›Coagulopathy

›Encephalopathy risk

›4 days to 2 weeks

›Recovery if survives acute liver failure

›Pitfall patterns

›Minimal symptoms despite severe injury

›Chronic supratherapeutic ingestion without clear time zero

›Extended release product with delayed peaks

03Physical Exam/exam20

Focused exam domains

›Vital signs and perfusion

›Hypotension

›Tachycardia

›Fever as alternate diagnosis clue

›Neurologic status

›Encephalopathy grade

›Asterixis

›GCS trend

›Abdominal exam

›RUQ tenderness

›Hepatomegaly

›Peritoneal signs as alternate diagnosis clue

›Bleeding and skin findings

›Ecchymoses

›Mucosal bleeding

›Jaundice

PITFALLS

›Common misses

›Normal early exam does not exclude severe toxicity

›Coingestants masking symptoms

›Delay in jaundice relative to AST and ALT rise

04Differential Diagnosis/ddx33

Acute liver injury and failure mimics

›Life threatening differentials

›Viral hepatitis (ICD-10 B15 to B19)

›Fever and systemic prodrome

›Exposure risks

›Ischemic hepatitis (shock liver)

›Hypotension history

›Very high AST and ALT with lactate elevation

›Toxic mushroom ingestion (Amanita)

›Delayed GI then liver injury

›Acute biliary obstruction or cholangitis

›Fever

›RUQ pain

›Cholestatic pattern

›Acute fatty liver of pregnancy

›Third trimester

›Hypoglycemia

›Coagulopathy

›HELLP syndrome

›Hypertension

›Thrombocytopenia

›Other hepatotoxic drugs

›Valproate

›Isoniazid

›Methotrexate

›Herbal supplements

Presentation based grouping

›Predominant altered mental status

›Sedative overdose

›Hypoglycemia

›Sepsis

›Predominant metabolic acidosis

›Salicylate toxicity

›Toxic alcohols

›Sepsis with lactic acidosis

05Laboratory Tests/lt45

Essential labs for all suspected toxicity

›Core panel

›Serum acetaminophen concentration

›First level at 4 hours post ingestion for known single acute ingestion

›Immediate level for unknown time or delayed presentation

›AST

›Early rise marker

›Peak often at 72 to 96 hours

›ALT

›Hepatocellular injury marker

›INR

›Synthetic function marker

›Early poor prognosis marker when rising

›Bilirubin

›Cholestasis and severity marker

›Creatinine

›Acute kidney injury marker

›Glucose

›Acute liver failure severity marker

›Electrolytes

›Potassium

›Bicarbonate

›Acid base and perfusion

›Venous blood gas

›pH

›Lactate

›Arterial blood gas if severe

›pH

›PaCO2 (mmHg)

›PaO2 (mmHg)

Coingestion and risk stratification labs

›Coingestion evaluation

›Salicylate concentration

›Ethanol concentration

›Pregnancy test when applicable

›ECG if coingestion suspected

›Repeated supratherapeutic ingestion evaluation

›Serum acetaminophen concentration

›Detectable level supports ongoing exposure

›AST and ALT trend

›INR trend

›Additional prognostic markers in severe cases

›Phosphate

›Rising level as poor prognosis marker in acute liver failure

›Ammonia

›Encephalopathy support

›Cerebral edema risk context

06Diagnostic Tests/dt46

Scoring Systems

›Risk and decision tools

›Rumack-Matthew nomogram

›Use case

›Single acute ingestion

›Known time of ingestion

›Level drawn at least 4 hours post ingestion

›Not valid

›Unknown time of ingestion

›Repeated supratherapeutic ingestion

›Staggered ingestion

›Chronic ingestion

›Treatment line concepts

›4 hour threshold 150 mg/L

›Approximate 0.99 mmol/L

›Some regions use lower threshold 100 mg/L

›Approximate 0.66 mmol/L

›King’s College criteria for acetaminophen acute liver failure

›High risk criteria set A

›Arterial pH < 7.30 after resuscitation

›High risk criteria set B

›INR > 6.5

›Creatinine > 300 micromol/L

›Grade III or IV encephalopathy

MRI

›Role of MRI

›Rare acute role

›Alternate diagnosis evaluation when uncertain

›Not routine for acetaminophen toxicity

›Management driven by labs and clinical course

›Role of CT

›Alternate diagnosis evaluation

›Abdominal pain with peritoneal signs

›Concern for other intraabdominal pathology

›Acute liver failure complications

›Cerebral edema evaluation when deterioration

›Not routine for acetaminophen toxicity

›Normal imaging does not exclude severe hepatotoxicity

Ultrasound

›Role of ultrasound

›Biliary obstruction evaluation

›Jaundice with cholestatic labs

›RUQ pain

›Liver parenchyma assessment

›Nonspecific findings common

›POCUS adjuncts in shock

›Cardiac function

›Volume assessment

›Free fluid assessment

07Disposition/dispo27

Level of care criteria

›Admission indications

›N-acetylcysteine initiated or indicated

›Nomogram above treatment line

›Unknown time with detectable level

›Repeated supratherapeutic ingestion with liver injury

›Evidence of hepatic injury

›AST or ALT above normal

›INR elevation

›Persistent vomiting or dehydration

›Coingestion requiring monitoring

›Intentional ingestion requiring psychiatric assessment

›ICU indications

›Encephalopathy

›INR rapidly rising

›pH < 7.30

›Lactate elevation with hemodynamic instability

›Hypoglycemia recurrent

›Renal failure with severe metabolic derangements

Discharge criteria

›Safe discharge pathway for acute single ingestion

›Serum acetaminophen below treatment line on nomogram

›Asymptomatic or improving

›Normal AST and ALT at appropriate timing when clinically indicated

›Reliable follow up and safety assessment

›Post discharge follow up

›Repeat AST and ALT within 24 to 72 hours if borderline or symptoms develop

›Primary care follow up for accidental overdosing education

›Mental health follow up when intentional ingestion

08Treatment/t97

Decontamination

›Activated charcoal

›Dosing

›1 g/kg orally

›Usual max 50 g

›Timing

›Within 2 hours for most cases

›Consider within 4 hours for massive ingestion

›Consider within 4 hours for extended release

›Contraindications

›Unprotected airway

›Active vomiting with aspiration risk

Antidote therapy

›N-acetylcysteine indications

›Nomogram at or above treatment line

›Unknown time with detectable acetaminophen

›Delayed presentation with suspected hepatotoxicity

›Repeated supratherapeutic ingestion with liver injury

›N-acetylcysteine IV standard 3 bag regimen

›Loading dose

›150 mg/kg in 200 mL over 60 minutes

›Second dose

›50 mg/kg in 500 mL over 4 hours

›Third dose

›100 mg/kg in 1000 mL over 16 hours

›Infusion volume adjustments

›Fluid restriction cases

›Pediatrics weight based fluid plans

›N-acetylcysteine IV simplified 2 bag regimen

›Loading dose

›200 mg/kg over 4 hours

›Maintenance dose

›100 mg/kg over 16 hours

›Use only per local protocol or toxicology guidance

›N-acetylcysteine oral regimen

›Loading dose

›140 mg/kg orally

›Maintenance doses

›70 mg/kg orally every 4 hours

›Total 17 doses

›Antiemetic support

›Ondansetron per local protocol if vomiting threatens completion

›N-acetylcysteine stop criteria

›Acetaminophen undetectable

›AST and ALT improving

›INR stable or improving

›Clinical status stable

›N-acetylcysteine extension criteria

›Persistent detectable acetaminophen

›Rising AST or ALT

›INR rising

›Ongoing hepatic failure features

Adverse reactions and mitigation

›N-acetylcysteine anaphylactoid reactions

›Typical features

›Flushing

›Urticaria

›Bronchospasm

›Hypotension

›Immediate management

›Pause infusion for moderate or severe reaction

›Antihistamines for urticaria

›Bronchodilator for bronchospasm

›Epinephrine if anaphylaxis physiology

›Rechallenge strategy

›Restart at slower rate after symptom control

›Continue NAC when possible due to high benefit

Adjuncts in massive overdose and severe toxicity

›Toxicology consultation triggers

›Massive ingestion suspected

›Early severe metabolic acidosis

›Altered mental status within hours

›Very high acetaminophen concentration

›Extended release ingestion with rising levels

›Fomepizole adjunct consideration

›Rationale

›CYP2E1 inhibition to reduce NAPQI formation

›Use only with toxicology guidance

›Off label practice in selected massive cases

›Hemodialysis consideration

›Indications in selected cases

›Severe metabolic acidosis refractory to resuscitation

›Altered mental status with high acetaminophen concentration

›Lactate elevation with shock physiology

›N-acetylcysteine dosing during dialysis

›Dose adjustments per toxicology guidance

Supportive care and acute liver failure management

›Glucose management

›Dextrose bolus for hypoglycemia

›Dextrose infusion for recurrent hypoglycemia

›Coagulopathy management

›Vitamin K consideration

›Suspected deficiency

›Blood products reserved for bleeding or procedures

›Encephalopathy management

›Airway protection when grade III or IV

›Head of bed elevation

›Avoid excessive sedation when possible

›Liver transplant pathway

›Early referral for acute liver failure

›King’s College criteria assessment

›Transfer to transplant capable center when criteria met or trending toward

09Special Populations/sp26

Pregnancy

›Pregnancy considerations

›Antidote benefit

›N-acetylcysteine crosses placenta

›Early treatment improves maternal and fetal outcomes

›Thresholds and algorithms

›Same risk stratification principles as nonpregnant adults

›Obstetric coordination

›Fetal monitoring for viable gestational age when severe maternal illness

Geriatric

›Geriatric considerations

›Higher risk contexts

›Malnutrition

›Polypharmacy with combination analgesics

›Fluid management

›IV NAC volume adjustments for heart failure risk

›Disposition

›Lower threshold for admission if frailty or poor support

Pediatrics

›Pediatric considerations

›Dose thresholds

›Acute ingestion risk commonly cited at 150 mg/kg or higher

›Chronic ingestion risk depends on daily dosing and duration

›Antidote dosing

›Weight based NAC regimens

›Strict fluid volume calculations

›Formulation pitfalls

›Liquid concentration errors

›Caregiver double dosing with multiple products

10Background/b39

Epidemiology

›Epidemiology essentials

›Common cause of acute liver failure in many regions

›Frequent unintentional overdoses from combination products

›High incidence of delayed presentations in intentional ingestions

Pathophysiology

›Mechanism

›Normal metabolism pathways

›Glucuronidation

›Sulfation

›Toxic pathway

›CYP mediated NAPQI formation

›Glutathione depletion

›Hepatocellular necrosis

›Risk modifiers

›CYP2E1 induction by chronic alcohol

›Reduced glutathione stores with malnutrition

›Clinical phases correlation

›Early mitochondrial toxicity in massive ingestions

›Early coma possible

›Early lactic acidosis possible

›Delayed hepatic necrosis timeline

›AST and ALT rise after first day

›Peak injury day 3 to 4

Therapeutic Considerations

›N-acetylcysteine rationale

›Glutathione precursor

›Detoxifies NAPQI

›Additional effects

›Improved hepatic blood flow

›Antioxidant effects

›Time sensitivity

›Best outcomes when started within 8 hours

›Benefit persists in established liver failure

›Activated charcoal rationale

›Reduces absorption when early

›May reduce need for NAC in borderline cases when given promptly

›Evidence framing

›N-acetylcysteine for at risk ingestions considered standard of care

›Consensus Class I recommendation

›Activated charcoal early considered beneficial in appropriate patients

›Consensus Class IIa recommendation

11Patient Discharge Instructions/pdi16

copy discharge instructions

›Discharge education

›Acetaminophen safe use

›Avoid more than one acetaminophen containing product at a time

›Follow label dosing intervals

›Avoid alcohol with frequent acetaminophen use

›Follow up plan

›Lab recheck timing if arranged

›Primary care follow up

›Return immediately for

›Persistent vomiting

›Worsening abdominal pain

›Confusion

›Yellowing of eyes or skin

›Dark urine

›New bleeding or easy bruising

›Fainting or severe weakness

12References/r10

Guidelines and key sources

›Clinical guidance sources

›American Academy of Clinical Toxicology and European Association of Poisons Centres and Clinical Toxicologists position statements on acetaminophen poisoning management

›Liver society guidance on acute liver failure and acetaminophen induced liver injury management

›Toxicology reference standards for Rumack-Matthew nomogram interpretation

›Transplant referral criteria references for King’s College criteria in acute liver failure

›Extracorporeal removal guidance resources for massive acetaminophen overdose scenarios

›Foundational studies and tools

›Rumack-Matthew acetaminophen nomogram original publication and validation work

›N-acetylcysteine clinical outcome studies emphasizing early administration

›Acute liver failure prognostic criteria development studies

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Reviewed by SymptomDx Medical Team · Last reviewed June 16, 2026

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