Methanol Poisoning

Basics

Description

  • Colorless, volatile liquid
  • Absorbed in 30–60 min
  • Metabolized by liver
  • Half-life 4–8 hr
  • Pathophysiology:
    • Metabolites formaldehyde and formic acid produce toxic effects
    • Inhibits cytochrome oxidase
  • Formic acid:
    • Determines degree of acidosis, visual symptoms, and mortality
    • Directly toxic to retinal and optic nerve tissue
  • Methanol metabolism:
    • Step 1: Methanol is converted to formaldehyde by liver enzyme alcohol dehydrogenase
    • Step 2: Formaldehyde is then rapidly converted by aldehyde dehydrogenase to formic acid
    • Step 3: Formic acid is degraded to carbon dioxide and water by folate-dependent mechanism
    • Steps 1 and 3 are rate-limiting steps

Etiology

Common sources of methanol:
  • Wood alcohol
  • Windshield washer fluid (>60% cases)
  • Inhalational abuse of carburetor cleaners
  • Fuel antifreeze solutions
  • Formalin
  • Gasoline
  • Paint solvents
  • Household cleaners
  • Sterno cans
  • Moonshine
  • Model airplane fuel
  • Photocopying fluid
  • Perfumes

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