Toxin
Methanol Poisoning
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Methanol Poisoning
, Methanol, Carbinol, Methyl Alcohol, Wood Alcohol, Wood Naptha
Pathophysiology
Methanol is a common industrial and household solvent (paint remover) and fuel additive
Antifreeze
Perfume
Pain solvents
Windshield washing fluid
Mechanisms of ingestion
Accidental Ingestion
by children
Alcoholism
with Methanol ingestion when
Alcohol
unavailable
Bootleg
Alcohol
(especially in developing nations, and where outlawed in conservative countries)
Industrial workers may inhale Methanol vapors (e.g. formaldehyde production, shellac processing)
Methanol is quickly absorbed by the gastrointestinal tract
Serum levels peak within 90 minutes of ingestion
Hepatic Metabolism
Methanol is metabolized into Formaldehyde (via
Alcohol
dehydrogenase)
Formaldehyde is metabolized into Formic Acid (via aldehyde dehydrogenase)
Formic acid is the primary toxin resulting in most of the ingestion-related damage and
Metabolic Acidosis
Formic acid is very slowly metabolized into carbon dioxide and water (via Tetrahydrofolate)
Symptoms
Symptom onset is delayed 12-24 hours from ingestion
Related to delay in metabolism to formic acid
Neurologic
Headache
Altered Level of Consciousness
Seizure
Extrapyramidal symptoms
Parkinsonism
Paresthesia
s
Tinnitus
(from
Ototoxicity
)
Cardiopulmonary
Dyspnea
Tachypnea
Kussmaul Respiration
s
Hypotension
(or
Hypertension
)
Bradycardia
Gastrointestinal
Nausea
or
Vomiting
Ocular
Blurred Vision
Double Vision
Progressive
Vision Loss
Lab
Serum Methanol level
Available at many community hospitals
Serum
Lipase
or
Serum Amylase
Metabolic panel
Decreased serum bicarbonate
Anion-gap
Metabolic Acidosis
Osmolal Gap
Hypomagnesemia
Hypophosphatemia
Differential Diagnosis
See
Altered Level of Consciousness
See Toxic Ingestion
See
Vision Loss
Ethylene Glycol
Toxicity
Liver
failure (hyperammonemia)
Renal Failure
(
Uremia
)
Head Injury
Encephalitis
Meningitis
Complications
Vision Loss
Formic acid causes
Optic Nerve
demyelination
Occurs with serum Methanol levels >20 mg/dl
Onset of ocular changes within 48 hours of ingestion
Parkinsonism
Methanol and metabolites cause
Basal Ganglia
damage resulting in Parkinsonian-like signs
Onset weeks after ingestion
Hemorrhagic
Pancreatitis
Occurs in more than two thirds of Methanol Poisoning
Death
Minimum lethal ingestion: 1 mg/kg
Even one tbs of 40% Methanol can kill an adult
Management
Fomepizole (Antizol)
Start immediately if Methanol toxicity is suspected
Hemodialysis
References
Korabathina in Ramachandran (2012) Methanol Toxicity, EMedicine
Leikin (1996)
Poisoning
and Toxicology, Lexi-Comp, Cleveland, p. 957-8
Swadron and Nordt in Majoewsky (2013) EM:Rap 13(8): 3
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