Emergency & Toxicology

Methanol and ethylene glycol poisoning

Clinical Overview and When to Suspect Toxic Alcohol Ingestion

— Methanol → formaldehyde → formic acid (retinal/optic nerve toxicity)

— Ethylene glycol → glycoaldehyde → glycolic acid → oxalic acid (renal tubular injury, hypocalcemia)

— Methanol: windshield washer fluid, moonshine, antifreeze additives, fuel additives, paint thinner, Sterno

— Ethylene glycol: automotive antifreeze (sweet taste), radiator fluid, brake fluid

— Unexplained HAGMA with elevated osmolar gap

— Inebriated-appearing patient without ethanol odor, or with ethanol level too low to explain symptoms

— Visual complaints ("snowfield vision," blurred vision, blindness) → methanol

— Flank pain, hematuria, oliguria, hypocalcemia, calcium oxalate crystals → ethylene glycol

— Intentional ingestion in a depressed patient, child exploring garage, alcoholic substituting when ethanol unavailable

— Symptoms often delayed 6–24 hours because parent alcohol must be metabolized

— Co-ingestion of ethanol delays onset (ethanol competes at alcohol dehydrogenase, ADH)

Step 3 management: In any altered patient with unexplained HAGMA, calculate both anion gap and osmolar gap, send a toxic alcohol panel and lactate, and if osmolar gap >10 with rising AG, start fomepizole empirically while toxicology levels return—delay to treatment is the single biggest predictor of permanent blindness (methanol) or dialysis dependence (EG).

Board pearl: "Drunk without the smell + metabolic acidosis + visual changes or flank pain" = toxic alcohol until proven otherwise.

Toxic alcohols = methanol and ethylene glycol (EG); both cause severe high anion gap metabolic acidosis (HAGMA) via toxic metabolites, not the parent alcohol itself.

Sources to recognize on stems:

When to suspect on a Step 3 ED scenario:

Timing pearls:

Mortality is high without prompt antidote; early empiric treatment saves lives—do not wait for confirmatory level if suspicion is strong.

Presentation Patterns and Key History

— Stage 1 (0–12 h): Neurologic/CNS — looks drunk, slurred speech, ataxia, nausea, vomiting; no ethanol smell; may progress to coma, seizures.

— Stage 2 (12–24 h): Cardiopulmonary — tachycardia, hypertension, tachypnea (Kussmaul from acidosis), pulmonary edema, hypocalcemia-driven QT prolongation, occasional cardiovascular collapse.

— Stage 3 (24–72 h): Renal (EG) — flank pain, oliguric AKI, calcium oxalate crystalluria. Methanol stage 3 = ocular — blurred vision, central scotomata, "looking at a snowfield," photophobia, blindness.

— Access: garage, mechanic, recent home repair, antifreeze in the home, illicit/homemade liquor (moonshine), windshield washer fluid in a soda bottle (pediatric)

— Intent: suicidal ideation, depression, prior attempts; inadvertent: alcoholic substitution

— Co-ingestants: ethanol (delays toxicity), benzodiazepines, acetaminophen

— Time of ingestion drives expected lab pattern: early = high osmolar gap, low AG; late = normalizing osmolar gap, high AG

Key distinction: Osmolar gap is highest early (parent alcohol still present) and falls as it is metabolized, while the anion gap rises later as toxic acids accumulate. A patient presenting late may have a normal osmolar gap but markedly elevated AG — do not be falsely reassured by a normal osm gap if the history fits.

Board pearl: Suspect EG in any "drunk" patient with flank pain + oxalate crystals in urine + hypocalcemia + AKI.

Three temporal phases are classically taught (especially for ethylene glycol, but methanol follows a similar arc):

Key history questions to drill on the stem:

Pediatric patients: small ingestion = big problem. A toddler sip of antifreeze (sweet, brightly colored) warrants ED evaluation.

Methanol-specific: ask about vision — "Can you read this?" Early blurry vision is reversible; once optic disc hyperemia → pallor → atrophy develops, blindness may be permanent.

Physical Exam Findings and Hemodynamic Assessment

— Tachypnea (respiratory compensation for HAGMA)

— Tachycardia, hypertension early; hypotension and shock late (myocardial depression, pulmonary edema)

— Hypothermia or normothermia; fever suggests alternate diagnosis or aspiration

— Slurred speech, ataxia, nystagmus, depressed mental status

— Seizures — especially with hypocalcemia (EG) or severe acidosis

— Coma in severe cases; cerebral edema and basal ganglia (putaminal) hemorrhage classically described with methanol

— Dilated, sluggish or fixed pupils = ominous

— Funduscopy: optic disc hyperemia early → papilledema → optic atrophy

— Decreased visual acuity, central scotomata, "snowfield vision"

CCS pearl: On a CCS case of suspected toxic alcohol, immediately order: continuous cardiac monitor, pulse oximetry, IV access x2, finger-stick glucose, fundoscopic exam, neuro checks q1h. Add calcium gluconate at bedside if QT is prolonged or tetany develops.

Board pearl: Fundoscopy showing hyperemic optic discs in an acidotic, "drunk" patient is methanol until proven otherwise — start fomepizole now.

General appearance: intoxicated without ethanol odor; can range from mild inebriation to coma. Late presentations may appear critically ill with Kussmaul respirations from profound metabolic acidosis.

Vital signs:

Neurologic:

Ocular exam (methanol-specific, high yield):

Cardiopulmonary: rales/pulmonary edema, S3 in late stage; QT prolongation on telemetry from hypocalcemia (EG)

Renal/abdominal (EG): costovertebral angle tenderness, suprapubic pain, oliguria

Skin/musculoskeletal: Wood's lamp of urine, mouth, or clothing may show fluorescence if antifreeze contained fluorescein (unreliable — do not exclude on this alone)

Tetany, Chvostek, Trousseau signs from hypocalcemia in EG

Diagnostic Workup — Initial Labs

— BMP (anion gap, bicarbonate, creatinine, glucose)

— Serum osmolality (measured by freezing point depression, not calculated)

— Calculated osmolality = 2(Na) + glucose/18 + BUN/2.8 + ethanol/3.7

— ABG/VBG with lactate

— Ethanol level (co-ingestant; affects gap calculations)

— Ionized calcium (EG → hypocalcemia)

— Urinalysis with microscopy (envelope-shaped or needle-shaped calcium oxalate crystals in EG)

— Acetaminophen + salicylate levels (universal tox screen)

— β-hCG in women of reproductive age

— ECG (QT for hypocalcemia)

— Normal <10; >25 strongly suggests toxic alcohol (also seen with isopropanol, mannitol, glycerol)

— Falls as parent alcohol is metabolized — a normal gap does not rule out late presentation

— Rises as toxic acids accumulate

— EG: glycolate is the primary acid driving AG

— Methanol: formate

Step 3 management: When osmolar gap is elevated and AG is rising, do not wait for confirmatory toxic alcohol levels (often send-out, hours-to-days turnaround). Treat empirically with fomepizole.

Board pearl: A patient with HAGMA + elevated osmolar gap + calcium oxalate crystalluria + hypocalcemia = ethylene glycol; HAGMA + elevated osmolar gap + visual changes = methanol.

Core lab panel to order simultaneously on arrival:

Osmolar gap = measured − calculated osmolality

Anion gap = Na − (Cl + HCO₃); >12 abnormal

Lactate caveat: EG can cause a falsely elevated lactate on some blood gas analyzers (glycolate cross-reacts) — a "lactate gap" between two analyzers is a clue

Urine Wood's lamp fluorescence for fluorescein in antifreeze — supportive but not sensitive or specific

Diagnostic Workup — Advanced and Confirmatory Studies

— Serum methanol and ethylene glycol levels by gas chromatography — gold standard, but often not available in real time at most US hospitals. Send to reference lab.

— Toxic threshold: >20 mg/dL for either generally warrants treatment; symptoms can occur at lower levels with delayed presentation.

— Rising AG with falling osmolar gap = ongoing metabolism of toxic alcohol

— Glycolate level (if available) correlates with EG toxicity better than EG itself in late presentation

— Formate level correlates with methanol toxicity and visual outcomes

— Non-contrast head CT in altered patient: methanol classically causes bilateral putaminal hemorrhage or necrosis and subcortical white matter injury; obtain if focal deficits, seizures, or persistent coma

— Chest X-ray if pulmonary edema or aspiration suspected

— Serial creatinine, urine output

— Urine microscopy: monohydrate (needle-shaped) and dihydrate (envelope-shaped) calcium oxalate crystals — dihydrate more common early, monohydrate late

— Renal ultrasound if obstruction is in the differential

Key distinction: A normal osmolar gap does not exclude toxic alcohol poisoning in a late-presenting patient; the anion gap is more reliable after 12–24 hours of metabolism. Trust the clinical picture and start antidote if presentation fits, even with reassuring gaps.

Board pearl: Bilateral putaminal lesions on head CT in an acidotic patient = methanol poisoning until proven otherwise.

Definitive testing:

Surrogate markers when levels unavailable:

Imaging:

Ophthalmology consult for methanol — formal visual acuity, color vision (Ishihara), fundoscopy, and visual evoked potentials for prognostication

Renal evaluation for EG:

ECG: prolonged QT from hypocalcemia → torsades risk

Pregnancy test, psych eval for intentional ingestion before disposition

Risk Stratification and First-Line Management Logic

— Documented serum methanol or EG >20 mg/dL

— Suspected ingestion AND osmolar gap >10

— Suspected ingestion AND HAGMA with no alternative explanation

— Strong clinical suspicion (history + symptoms) even if labs pending

— Activated charcoal NOT useful — toxic alcohols poorly bound and rapidly absorbed

— Gastric lavage only if presenting within ~60 minutes of large ingestion (rarely useful)

1. ADH inhibition with fomepizole (preferred) or ethanol (alternative)

2. Cofactor therapy to shunt remaining toxic metabolites:

— Methanol → folinic acid (leucovorin) or folate to accelerate formate → CO₂ + water

— Ethylene glycol → thiamine (shunts glyoxylate → α-hydroxy-β-ketoadipate) and pyridoxine (shunts to glycine)

3. Hemodialysis for severe poisoning (see chunk 8)

— Sodium bicarbonate for severe acidosis (pH <7.30) — also enhances renal excretion of formate

— IV calcium gluconate for symptomatic hypocalcemia or QT prolongation in EG (use cautiously — may worsen oxalate deposition)

— Aggressive IV fluids to maintain urine output in EG

— Avoid CNS depressants when possible

Step 3 management: Stratify severity by pH, AG, end-organ injury (vision, kidney, CNS), and toxic alcohol level. Indications for hemodialysis include pH <7.15–7.25, severe AKI, visual symptoms (methanol), refractory electrolyte abnormalities, or very high levels (>50 mg/dL traditionally, lower thresholds now common with fomepizole availability).

Board pearl: Order fomepizole + cofactors + dialysis evaluation simultaneously — don't sequence them.

ABCs first: airway protection for obtunded patients (GCS ≤8 → intubate), supplemental O₂, IV access, monitor.

Empiric treatment triggers (treat if any of the following):

Decontamination:

Three pillars of treatment:

Supportive measures:

Pharmacotherapy — First-Line: Fomepizole and Cofactors

— Mechanism: competitive ADH inhibitor with ~8000× higher affinity than ethanol; prevents conversion of methanol/EG to toxic metabolites

— Dose: 15 mg/kg IV load, then 10 mg/kg q12h × 4 doses, then 15 mg/kg q12h (induces its own metabolism)

— During hemodialysis: q4h dosing or continuous infusion (dialyzable)

— Endpoint: continue until methanol/EG level <20 mg/dL AND patient asymptomatic with normal pH and AG

— Advantages over ethanol: no CNS depression, no hypoglycemia, predictable kinetics, no level monitoring, safer in children and pregnancy

— Disadvantages: cost (~$1000–2000/vial), occasional headache/nausea

— Load 0.6–0.8 g/kg IV (10% solution) or oral; maintenance to keep level 100–150 mg/dL

— Requires frequent level checks, glucose monitoring, ICU

— Risks: CNS depression, hypoglycemia (especially in children), pancreatitis

— Methanol: folinic acid (leucovorin) 1–2 mg/kg IV q4–6h (preferred) or folate; accelerates formate clearance

— Ethylene glycol:

— Thiamine 100 mg IV q6h — shunts glyoxylate to α-hydroxy-β-ketoadipate

— Pyridoxine (B6) 50–100 mg IV q6h — shunts glyoxylate to glycine

— Combined, these reduce oxalate formation and renal injury

Board pearl: Fomepizole + folinic acid = methanol cocktail. Fomepizole + thiamine + pyridoxine = ethylene glycol cocktail. Memorize these.

Step 3 management: Start cofactors immediately — they're cheap, safe, and no level needed to give.

Fomepizole (4-methylpyrazole) — first-line ADH inhibitor:

Ethanol (alternative when fomepizole unavailable):

Cofactor therapy (cheap, low-risk, give to all):

Sodium bicarbonate: target pH >7.30; enhances formate ionization and renal excretion

IV calcium: for symptomatic hypocalcemia, tetany, seizures, QT prolongation — but use judiciously in EG (precipitates more oxalate)

Hemodialysis and Advanced Management

— Severe metabolic acidosis: pH <7.15 (some sources <7.25), especially if refractory to bicarbonate

— End-organ injury: visual symptoms or fundoscopic changes (methanol); AKI or rising creatinine (EG)

— Hemodynamic instability or altered mental status

— Methanol or EG level >50 mg/dL (traditional threshold; lower thresholds increasingly used when fomepizole alone can keep up with elimination)

— Electrolyte abnormalities refractory to therapy

— Mechanical ventilation as needed; maintain minute ventilation to compensate for acidosis — do not allow PCO₂ to rise after intubation

— Vasopressors for shock; avoid agents that prolong QT in EG with hypocalcemia

— Ophthalmology and nephrology consults as appropriate

— Poison control (1-800-222-1222) — call early; they can assist with sourcing fomepizole and guiding therapy

CCS pearl: On a CCS case, the order set for severe toxic alcohol ingestion looks like: fomepizole IV load → folinic acid OR thiamine+pyridoxine → bicarbonate drip → call nephrology for emergent HD → ICU admission → ophthalmology consult (methanol) → poison control. Move quickly — sequence in parallel.

Board pearl: Visual changes from methanol = emergent dialysis indication, regardless of level.

Hemodialysis (HD) is definitive therapy for severe toxic alcohol poisoning — removes both parent alcohol and toxic metabolites, and corrects acidosis/electrolyte derangements simultaneously.

Indications for HD (any of):

HD modifies fomepizole dosing: increase to q4h during dialysis (fomepizole is dialyzable)

CRRT is acceptable if HD unavailable or patient unstable, though clearance is slower

Endpoint of HD: toxic alcohol level <20 mg/dL, normalized pH and AG, resolution of symptoms

Adjuncts:

Newer concept: fomepizole-only management without HD is reasonable for early, less severe EG/methanol poisoning with normal renal function, no visual symptoms, and pH >7.30, allowing endogenous elimination over days

Special Populations — Elderly and Renal/Hepatic Impairment

— Higher baseline comorbidity (CKD, CAD, dementia) magnifies organ injury

— Delirium and altered mental status may be misattributed to baseline cognitive impairment or UTI — maintain high suspicion for toxic ingestion if history is unclear

— Polypharmacy → drug interactions with ethanol therapy (benzodiazepines, opioids, sulfonylureas)

— Lower physiologic reserve → earlier intubation and dialysis thresholds reasonable

— Social history: confirm medication review and possible accidental ingestion (mistaking antifreeze for a beverage, undiagnosed cognitive impairment)

— Baseline AKI on CKD complicates EG management

— Lower threshold for HD in any CKD patient with EG exposure — endogenous clearance is impaired

— Adjust dialysis duration based on residual clearance

— Monitor for delayed rebound in toxic metabolite levels after HD ends — extend fomepizole

— ADH and aldehyde dehydrogenase activity reduced → slower production of toxic metabolites but also slower clearance

— Fomepizole metabolized hepatically (CYP-mediated); no major adjustment typically needed for short-term toxic alcohol treatment, but monitor

— Avoid ethanol therapy in cirrhotic patients — worsens encephalopathy, hypoglycemia, and coagulopathy

— Fomepizole inhibits CYP2E1 → potential interaction with other CYP2E1 substrates (acetaminophen, isoniazid)

— Caution in concomitant acetaminophen overdose — fomepizole may actually be protective by reducing NAPQI formation (emerging evidence)

Step 3 management: In elderly or CKD patients with confirmed EG/methanol ingestion, lean toward early hemodialysis even at lower levels — physiologic reserve is limited and consequences of under-treatment (permanent blindness, dialysis dependence) outweigh procedural risk.

Board pearl: Prefer fomepizole over ethanol in elderly, hepatic disease, and any patient where CNS depression or hypoglycemia would be especially harmful.

Elderly patients:

Chronic kidney disease:

Hepatic impairment:

Drug interactions:

Special Populations — Pregnancy and Pediatrics

— Both methanol and ethylene glycol cross the placenta; fetal toxicity well documented

— Maternal acidosis → fetal acidosis → fetal demise risk

— Fomepizole is preferred (Pregnancy Category C, but safer than ethanol which causes fetal alcohol effects, hypoglycemia, and CNS depression even with short courses)

— Cofactors are safe and indicated: folinic acid (methanol), thiamine + pyridoxine (EG)

— Hemodialysis is safe in pregnancy with continuous fetal monitoring (≥24 weeks) — do not delay

— Multidisciplinary care: OB, MFM, toxicology, nephrology

— Antifreeze ingestion is a classic pediatric exposure — brightly colored, sweet-tasting

— Even small volumes (a sip, ~5 mL) of concentrated EG can produce toxic levels in a toddler

— Symptoms develop faster in children due to body weight–dose relationships

— Fomepizole dosing same per kg as adults; preferred over ethanol in children (ethanol → severe hypoglycemia)

— Check glucose q1–2h if ethanol therapy is unavoidable

— Pediatric HD requires specialized center → arrange transfer early

— Mandatory reporting: evaluate for neglect/child safety if access to antifreeze was preventable

— Intentional ingestion: psychiatric evaluation, suicide risk screening

— Inhalant abuse: methanol from windshield washer fluid sniffing

— Substance use history, social work involvement

Step 3 management: For pregnant patients, fomepizole + cofactors + early HD with continuous fetal monitoring. For pediatric patients, fomepizole over ethanol every time, and arrange transfer to a pediatric center with dialysis capability if not available locally.

Board pearl: A toddler with vomiting, ataxia, and an open garage — check for antifreeze ingestion, call poison control, and treat empirically while awaiting levels.

Pregnancy:

Pediatrics:

Adolescents:

Complications and Adverse Outcomes

— Permanent blindness from optic nerve demyelination and atrophy — most feared sequela

— Parkinsonism and dystonia from putaminal necrosis/hemorrhage on CT

— Cerebral edema, seizures, coma

— Pancreatitis (acute hemorrhagic) — order lipase if abdominal pain

— Mortality 20–40% even with treatment in severe cases

— Acute kidney injury / acute tubular necrosis from oxalate deposition — may require prolonged or permanent dialysis if treatment delayed

— Hypocalcemia → tetany, seizures, prolonged QT and torsades

— Pulmonary edema, ARDS, myocardial dysfunction (stage 2)

— Cranial neuropathies (especially CN VII, VIII) — delayed, weeks after exposure

— Cerebral edema, coma

— Ethanol therapy: hypoglycemia (especially pediatric), CNS depression, pancreatitis, hypotension

— Fomepizole: rare — headache, nausea, mild transaminitis

— Hemodialysis: line complications, hypotension, electrolyte shifts

— Bicarbonate: hypernatremia, volume overload, paradoxical CSF acidosis if given rapidly

— Calcium: tissue necrosis if extravasated; worsens oxalate deposition in EG

— Methanol survivors: visual deficits (scotomata, blindness), parkinsonism, cognitive impairment

— EG survivors: CKD or ESRD, peripheral/cranial neuropathy

— Psychiatric: post-intentional-ingestion depression, PTSD

Key distinction: Methanol kills (or blinds) the brain and eyes; ethylene glycol kills the kidneys (and heart via hypocalcemia). The treatments overlap but the sequelae are organ-specific — counsel patients and families accordingly.

Board pearl: Delayed cranial neuropathies (5–20 days post-EG ingestion) are a classic boards finding and may resolve over months — anticipate and counsel.

Methanol-specific complications:

Ethylene glycol–specific complications:

Treatment-related complications:

Long-term sequelae:

When to Escalate Care — ICU, Consult, and Triage

— Any patient receiving fomepizole or ethanol infusion

— pH <7.30, ongoing acidosis, or need for bicarbonate drip

— Altered mental status, seizures, hemodynamic instability

— Need for hemodialysis

— Methanol with visual symptoms or EG with AKI/hypocalcemia

— Medical toxicology or regional poison control center (1-800-222-1222) — assists with antidote sourcing, dosing, dialysis indication

— Nephrology — emergent HD planning

— Ophthalmology — formal visual exam, fundoscopy, prognostication (methanol)

— Psychiatry — for intentional ingestion, prior to discharge

— Social work — pediatric exposures, suicide attempts, substance use

— If your facility lacks hemodialysis capability or pediatric HD and patient meets HD criteria → arrange emergent transfer

— Start fomepizole and cofactors before transport — do not delay treatment for transfer logistics

— Ensure adequate antidote supply for the transfer window

— Intentional ingestion = psychiatric hold (1:1 sitter) until cleared

— Accidental pediatric = social work, child safety evaluation, home environment review

CCS pearl: On a CCS case, your first 30 minutes should include: IV access, labs sent, fomepizole + cofactors started, poison control called, nephrology consulted, ICU bed requested, ophthalmology consulted if methanol, psychiatry if intentional. Parallel orders, not serial.

Step 3 management: Never discharge a suspected toxic alcohol patient from the ED based on a single normal level if presentation was delayed — observe with serial AG and osm gaps over 6–12 hours.

ICU admission criteria (essentially all confirmed/suspected toxic alcohol poisonings):

Consultations to call early (don't sequence; call simultaneously):

Transfer considerations:

Step-down/floor: appropriate only once acidosis resolved, levels <20 mg/dL, fomepizole completed, no end-organ injury progression

Disposition pearls:

Key Differentials — Other Causes of Elevated Osmolar Gap and HAGMA

— Isopropanol (rubbing alcohol): elevated osmolar gap WITHOUT acidosis; produces acetone (ketosis without acidosis); fruity breath, hemorrhagic gastritis, CNS depression. Treatment is supportive ± HD; ADH inhibition NOT needed because metabolite (acetone) is not acidic.

— Ethanol: most common cause of mildly elevated osmolar gap; account for it in osm gap calculation

— Diethylene glycol (brake fluid contaminant): renal and neurologic toxicity; treat like EG

— Propylene glycol (IV lorazepam, phenobarbital diluent): HAGMA + osmolar gap in ICU patients on prolonged infusions

— Mannitol, glycerol, sorbitol: elevated osm gap without acidosis

— Methanol

— Uremia

— DKA / alcoholic ketoacidosis / starvation ketoacidosis

— Propylene glycol / paraldehyde

— Iron, Isoniazid

— Lactic acidosis (sepsis, ischemia, metformin)

— Ethylene glycol

— Salicylates

— Methanol, ethylene glycol — the classic pair

— Alcoholic ketoacidosis (mildly elevated osm gap from ethanol + ketones)

— Severe lactic acidosis can occasionally elevate osm gap

— DKA with elevated ketones

Key distinction: Isopropanol = osm gap without AG acidosis; methanol/EG = osm gap with AG acidosis. This single distinction is one of the highest-yield USMLE points.

Board pearl: A patient who drinks mouthwash and presents intoxicated with normal pH = isopropanol or ethanol; one who drinks moonshine and presents acidotic with vision loss = methanol; one who drinks antifreeze and presents acidotic with flank pain = ethylene glycol.

Other toxic alcohols and substances causing elevated osmolar gap:

Other HAGMA causes (mnemonic MUDPILES or GOLD MARK):

Combined pattern (HAGMA + osmolar gap):

Key Differentials — Other-Category Causes

— HAGMA, but glucose elevated, ketones in urine/serum, no osmolar gap (unless coexistent ethanol/methanol)

— History of diabetes, polyuria, polydipsia

— Chronic alcohol use + recent binge + decreased intake + vomiting

— HAGMA from β-hydroxybutyrate; mildly elevated osm gap from residual ethanol

— Treat with dextrose-containing fluids and thiamine; usually resolves rapidly

— Mixed respiratory alkalosis + HAGMA; tinnitus, hyperventilation, hyperthermia, diaphoresis

— Treat with alkalinization, glucose, HD for severe cases

— Fever, hypotension, infection source; elevated lactate; osm gap normal

— Elevated BUN/creatinine, history of CKD; symptomatic uremic syndrome

— Toxic ingestion with HAGMA but distinct histories

— Cyanide: smoke inhalation, almond breath, lactate >10

— CO: closed-space fire, headache, elevated COHb

— Altered mental status without acidosis or osm gap; head CT diagnostic

— Ataxia + ophthalmoplegia + confusion in alcoholic — may coexist with toxic alcohol ingestion; give thiamine empirically

Key distinction: A patient with the classic "drunk without ethanol smell + HAGMA" triad mandates methanol/EG workup. Do not anchor on DKA, AKA, or sepsis without checking osm gap and toxic alcohol levels.

Board pearl: Always check glucose, lactate, ketones, salicylate, acetaminophen, ethanol, and osm gap in any unexplained HAGMA — this panel catches nearly every relevant toxidrome.

Diabetic ketoacidosis (DKA):

Alcoholic ketoacidosis (AKA):

Salicylate toxicity:

Sepsis / lactic acidosis:

Uremia:

Iron, INH, cyanide, carbon monoxide:

Cerebrovascular event / intracranial pathology:

Wernicke encephalopathy:

Hypoglycemia, hypothermia, postictal state: altered mental status mimics; check glucose, temperature, witness reports

Secondary Prevention and Discharge Planning

— Toxic alcohol level <20 mg/dL (or undetectable)

— Resolution of acidosis (normal AG, pH >7.35)

— No ongoing end-organ injury (stable creatinine, no progressive visual loss)

— Completion of fomepizole course

— Psychiatric clearance if intentional ingestion

— No specific outpatient antidote needed once cleared

— Folate supplementation may be continued for several days after methanol exposure (cheap, safe)

— Treatment of underlying alcohol use disorder: naltrexone, acamprosate, disulfiram (caution — disulfiram in someone who might drink methanol-contaminated alcohol is dangerous; counsel carefully)

— Antidepressants/SSRIs if intentional ingestion related to mood disorder; partner with psychiatry on initiation

— Store antifreeze and windshield washer fluid in original, labeled containers, out of reach of children, locked if cognitively impaired adult lives in home

— Discuss less-toxic alternatives (propylene glycol–based antifreeze)

— Never drink unknown or homemade alcoholic beverages ("moonshine"); methanol contamination is a known cause of outbreaks

— Discuss bittering agents in antifreeze (some states mandate)

— Outpatient addiction medicine, AA, structured rehab

— Address comorbid depression, suicidality

— Childproofing education, garage safety, poison control number prominently displayed

Step 3 management: Before discharge, always: (1) confirm psychiatric clearance for intentional ingestion, (2) provide written safety/storage instructions for accidental exposure, (3) refer for substance use disorder treatment if alcohol-related, (4) schedule follow-up within 1–2 weeks.

Board pearl: Methanol "outbreak" stems usually involve moonshine, hand sanitizer ingestion, or contaminated industrial alcohol — counsel high-risk patients.

Disposition prerequisites (all must be met):

Discharge medications and therapies:

Prevention counseling (high yield on Step 3):

Substance use disorder referral:

Pediatric exposures:

Follow-Up, Monitoring, and Rehabilitation

— Primary care visit: review labs, medication reconciliation, screen for ongoing substance use and depression

— Renal follow-up (EG): BMP for creatinine trend; nephrology consultation if AKI was severe or did not fully resolve. Some patients require ongoing dialysis for weeks to months; rare cases progress to ESRD requiring transplant evaluation

— Ophthalmology follow-up (methanol): formal visual acuity, visual field testing, fundoscopy at 1 week and 1 month; some deficits improve over weeks, others permanent

— Neurology if persistent neurologic deficits (parkinsonism from methanol, cranial neuropathies from EG)

— Annual renal function checks if any AKI history (EG)

— Visual rehabilitation services, low-vision specialists, occupational therapy for blind/visually impaired methanol survivors

— Driving restrictions for visually impaired patients — document discussion and notify DMV per state law

— Mandatory after intentional ingestion: outpatient psychiatry within 1 week of discharge

— Crisis hotline numbers, safety plan, removal of lethal means from home

— Treat underlying depression, anxiety, substance use disorder

— Physical/occupational therapy for parkinsonism, neuropathy

— Vocational rehabilitation if visual or cognitive deficits affect employment

— Support groups, family counseling

— Alcohol abstinence and SUD treatment

— Lethal means restriction (firearms, medications, household toxins)

— Recognition of relapse warning signs

Step 3 management: A methanol survivor with permanent visual loss requires a coordinated handoff: low-vision rehab, social work for disability benefits, driving cessation, psychiatry, and primary care — schedule all referrals before discharge, not after.

Board pearl: Always check renal function at 3 months in EG survivors — late CKD progression is common and frequently underdiagnosed.

Short-term follow-up (within 1–2 weeks of discharge):

Long-term monitoring:

Psychiatric follow-up:

Rehabilitation:

Counseling topics:

Ethical, Legal, and Patient Safety Considerations

— Acutely intoxicated/encephalopathic patients lack decision-making capacity — treat under emergency doctrine (implied consent) for life-saving therapy (fomepizole, dialysis, intubation)

— Document capacity assessment carefully; reassess when sober

— If patient refuses care after intentional ingestion but lacks capacity → involve psychiatry, consider involuntary hold under state mental health statute

— Suspected child neglect or abuse (pediatric antifreeze exposure with inadequate supervision): mandatory report to child protective services

— Elder abuse/neglect: report if cognitively impaired adult had preventable access

— Suicide attempts: psychiatric evaluation; involuntary hold if imminent risk

— Cluster of cases (multiple methanol poisonings from a single source — e.g., contaminated alcohol) → notify public health department

— Antidote handoff during transfer: ensure fomepizole continues during ambulance/helicopter transport — common point of treatment lapse

— Sign-out at shift change: explicit communication about pending toxic alcohol level, AG trend, next fomepizole dose

— Discharge instructions: written, in patient's preferred language, with teach-back; ensure psych follow-up scheduled, not just "recommended"

— Intentional ingestion: balance confidentiality with safety; family may need to be involved in safety planning even over patient objection if imminent risk

— Fomepizole is expensive and not stocked everywhere — rural and resource-limited hospitals may need to use ethanol therapy or transfer; recognize this disparity

— Poison control is free and available 24/7 — utilize regardless of insurance status

Step 3 management: In any intentional ingestion, the discharge plan must include lethal means restriction counseling, written psychiatric follow-up appointment within 7 days, and 24/7 crisis line number — not just verbal advice. Document all three.

Board pearl: Failure to arrange psychiatric follow-up before ED discharge of a survivor of intentional overdose is a classic Step 3 safety/quality vignette — always set the appointment, don't just refer.

Informed consent and capacity:

Mandatory reporting:

Transitions of care risks (high Step 3 yield):

Confidentiality:

Equity and access:

High-Yield Associations and Rapid-Fire Clinical Facts

— Methanol: folinic acid (or folate)

— EG: thiamine + pyridoxine

Board pearl: Memorize the three triads:

— Methanol: HAGMA + osm gap + visual loss

— EG: HAGMA + osm gap + flank pain/oxalate crystals/hypocalcemia

— Isopropanol: osm gap + ketosis without acidosis

Step 3 management: When in doubt, start fomepizole + cofactors + call poison control — these three actions cover 90% of toxic alcohol management.

Methanol metabolism: Methanol → (ADH) → formaldehyde → (ALDH) → formic acid (toxic, optic nerve)

Ethylene glycol metabolism: EG → (ADH) → glycoaldehyde → glycolic acid → glyoxylic acid → oxalic acid (renal)

Fomepizole > ethanol in nearly every scenario (safer, predictable, no level monitoring)

Cofactors:

Visual symptoms ("snowfield vision," central scotomata, blindness) = methanol

Calcium oxalate crystals + hypocalcemia + AKI = ethylene glycol

Bilateral putaminal hemorrhage on CT = methanol

Cranial neuropathies 5–20 days post-ingestion = ethylene glycol

Wood's lamp fluorescence of urine/mouth/clothes = some antifreeze (low sensitivity)

Isopropanol = osm gap without acidosis; ketones without acidosis; no antidote needed

Osmolar gap falls as parent alcohol is metabolized; anion gap rises as toxic metabolites accumulate

Lactate gap: glycolate falsely elevates lactate on some analyzers in EG → discrepancy between two analyzers is a clue

Treat empirically: don't wait for confirmatory levels (often send-out)

HD indications: pH <7.15–7.25, visual symptoms (methanol), AKI (EG), level >50 mg/dL (traditional), refractory acidosis, hemodynamic instability

Poison Control: 1-800-222-1222 (US, 24/7)

Pregnancy: fomepizole + cofactors + HD safer than ethanol

Pediatric: antifreeze is the classic sweet, brightly colored ingestion

Disulfiram-like reaction does NOT occur with fomepizole/methanol/EG — different mechanism

Activated charcoal: NOT effective for toxic alcohols

Methanol survival often involves permanent visual loss and/or parkinsonism

EG survival often involves CKD or transient dialysis dependence

Board Question Stem Patterns

— "A 45-year-old man with chronic alcoholism is brought to the ED after drinking 'homemade liquor.' He complains of blurred vision and 'looking at a snowfield.' BP 130/80, RR 28, GCS 13. Labs: pH 7.10, HCO3 8, AG 28, osm gap 22. What is the next step?"

— Answer: Fomepizole IV + folinic acid + emergent hemodialysis + ophthalmology consult

— "A 28-year-old man with depression is found in his garage next to an open container of antifreeze. He is somnolent with flank pain. UA shows envelope-shaped crystals. Ca 6.8, Cr 2.5, pH 7.15, AG 26."

— Answer: Fomepizole + thiamine + pyridoxine + IV calcium (if symptomatic) + hemodialysis

— Patient drinks rubbing alcohol; intoxicated, fruity breath, elevated osm gap, NORMAL pH, ketones present, no acidosis

— Answer: Supportive care; no ADH inhibition needed

— Two lactate values differ markedly between point-of-care and central lab in an acidotic patient → suspect ethylene glycol (glycolate cross-reactivity)

— Patient with HAGMA but normal osm gap and history of "drinking something" 36 hours ago → don't be falsely reassured; treat empirically

— Patient appears clinically well 8 hours post-ingestion because ethanol delays metabolism → still treat with fomepizole; symptoms may be deferred

— Toddler from a home with open garage, vomiting, ataxia, "drank something sweet" → ethylene glycol; fomepizole, NOT ethanol

— Pregnant woman with intentional antifreeze ingestion → fomepizole, cofactors, HD with fetal monitoring

— Patient with HAGMA + osm gap and uncertain ingestion — order set: fomepizole, folinic acid + thiamine + pyridoxine (cover both until known), bicarb, nephrology consult, poison control, ICU admit

Board pearl: If the stem mentions "windshield washer fluid," "moonshine," or "antifreeze" — the diagnosis is in the source. Pick the antidote and dialysis.

Step 3 management: Always answer "fomepizole" over "ethanol" when both are listed as options unless explicitly stated that fomepizole is unavailable.

Classic methanol stem:

Classic ethylene glycol stem:

Isopropanol distractor:

Lactate gap stem:

Late presentation stem:

Co-ingestion of ethanol:

Pediatric stem:

Pregnancy stem:

CCS-style stem:

One-Line Recap

In any patient with unexplained high anion gap metabolic acidosis and an elevated osmolar gap, suspect methanol or ethylene glycol poisoning and treat empirically with fomepizole plus targeted cofactors (folinic acid for methanol; thiamine and pyridoxine for ethylene glycol), with emergent hemodialysis for severe acidosis, end-organ injury (visual symptoms or AKI), or hemodynamic instability — never delay treatment awaiting confirmatory levels.

Board pearl: The three winning actions on any toxic alcohol stem are fomepizole + cofactors + dialysis evaluation — and the antidote always wins over waiting for the confirmatory level.

Step 3 management: Lethal-means restriction, mandatory psychiatric follow-up, and substance use disorder linkage are non-negotiable elements of the discharge plan for any intentional ingestion.

Recognize: "Drunk without ethanol smell" + HAGMA + osm gap >10 → toxic alcohol until proven otherwise. Methanol = visual loss + putaminal injury; ethylene glycol = AKI + calcium oxalate crystals + hypocalcemia.

Treat in parallel: Fomepizole (15 mg/kg load, then 10 mg/kg q12h) + cofactors + bicarbonate for pH <7.30 + IV calcium for symptomatic hypocalcemia + nephrology consult for emergent HD. Activated charcoal is NOT useful. Call poison control (1-800-222-1222) early.

Dispose safely: ICU admission for all confirmed cases; psychiatric clearance before discharge for intentional ingestion; ophthalmology and nephrology follow-up; substance use disorder treatment referral; safety counseling on storage of household toxins; arrange psychiatric appointment within 7 days before discharge, not after.

Don't miss: Isopropanol (osm gap WITHOUT acidosis — no antidote needed), late presentation (normal osm gap but rising AG — still treat), pregnant patients (fomepizole + HD with fetal monitoring), and the lactate gap clue (glycolate cross-reactivity falsely elevates lactate in ethylene glycol).