Methanol Toxicity

Methanol (wood alcohol), found in windshield washer fluid, industrial solvents, and bootleg spirits, is metabolized by alcohol dehydrogenase to formaldehyde, which is then rapidly converted by aldehyde dehydrogenase to formic acid, the primary toxic metabolite. Formic acid inhibits mitochondrial cytochrome c oxidase (complex IV of the electron transport chain), blocking oxidative phosphorylation and causing cellular energy failure and lactic acid accumulation, producing severe metabolic acidosis. Formic acid has particular affinity for the optic nerve and basal ganglia, causing retinal toxicity (dilated, poorly reactive pupils; 'snowstorm' visual field; blindness) and putaminal necrosis (parkinsonian features). There is a characteristic latent period of 12-24 hours between ingestion and symptom onset while methanol is metabolized to formic acid, during which the patient may appear only mildly intoxicated. The nurse monitors ABGs (severe anion gap metabolic acidosis), calculates osmolar gap (elevated early before metabolism), monitors visual acuity and pupillary responses, administers fomepizole or ethanol infusion to block alcohol dehydrogenase, administers folinic acid (leucovorin) to enhance formic acid metabolism, assists with emergent hemodialysis for severe cases, and monitors for renal failure and neurological sequelae.