How do I manage ethylene glycol toxicity differently in dogs versus cats and what is the treatment window?

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The critical species difference is the antidote: fomepizole (4-methylpyrazole, 4-MP) is the first-line antidote in dogs at a standard canine protocol, while cats require a substantially higher dose of 4-MP, and the treatment window is 8 hours post-ingestion for dogs. The treatment window is 8 hours from ingestion in dogs — dogs treated within this window carry a good prognosis, while delays are associated with high mortality.8 The same 8-hour window applies broadly to both species, as adequate treatment must be initiated within 8 hours of ingestion to prevent irreversible acute renal failure.5 In cats, 4-MP is dosed at 125 mg/kg IV as the initial dose, followed by 31.25 mg/kg IV at 12, 24, and 36 hours. This regimen is safe and effective for naturally occurring ethylene glycol (EG) toxicity in cats, with all treated cats surviving to discharge in reported cases.7 Increased bicarbonate concentrations are observed after IV 4-MP administration in cats, consistent with correction of metabolic acidosis.7 The minimum lethal dose differs substantially between species. The minimum lethal dose of undiluted EG is 1.5 mL/kg for cats and 4.4–6.6 mL/kg for dogs, making cats significantly more susceptible.1 The case fatality rate is 78%–96% for cats and 44%–70% for dogs.1 Hemodialysis is an additional treatment option when antidote therapy alone is insufficient, as it removes both the parent compound and toxic metabolites.5 This is particularly relevant when presentation is delayed beyond the antidote window or when oligoanuric renal failure has already developed.5 Supportive care targets metabolic acidosis and renal failure — EG metabolites cause severe metabolic acidosis and renal tubular epithelial damage, and approximately 50% of ingested EG is excreted unchanged by the kidneys within the first hours, making early fluid diuresis relevant alongside antidote therapy.2 A positive whole-blood EG test kit result requires clinical correlation. The Catachem quantitative kit reads hi