Methanol and ethylene glycol Methanol

Toxicity mainly arises due to oxidation of methanol to formic acid and formaldehyde. The oxidative pathway is an enzymatic process involving alcohol dehydrogenase but proceeds at 20% of the rate of ethanol oxidation.

Clinical features

Clinical features of poisoning include blindness (due to concentration of methanol in the vitreous humour), severe metabolic acidosis, headache, nausea, vomiting and abdominal pain.

Management

• Metabolism of methanol is slow so treatment will need to be prolonged (several days).

• Treatment includes gastric emptying (within 4h of ingestion), sodium bicarbonate titrated to correct arterial pH and ethanol to saturate the oxidative pathway.

• On presentation 1ml/kg ethanol (50%) is given orally followed by 0.5ml/kg 2-hrly for 5 days.

• Alternatively, metabolism can be blocked by 4-methyl pyrazole (fomepizole) which can be infused or injected 12-hrly.

• If methanol levels are >1000mg/l haemodialysis is used until levels are <250mg/l.

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