Antifreeze (Ethylene Glycol) Poisoning

Antifreeze poisoning is uniquely cruel because the poison is appealing. Ethylene glycol is sweet, and a cat that walks through a coolant spill will happily lick it from its paws. The lethal dose is alarmingly small — a matter of a teaspoon or two for an average cat, and sometimes less.

The illness unfolds in stages, which is part of what makes it so dangerous. In the first few hours the cat looks drunk: unsteady, disorientated, perhaps vomiting and drinking excessively. Owners who miss this stage, or who put it down to a scrap with another cat, may then see an apparent improvement. Behind that false recovery, the liver is busy converting ethylene glycol into glycolic and oxalic acid, and calcium oxalate crystals are forming inside the kidney tubules. Two to three days later the cat crashes into acute kidney failure — profoundly unwell, producing little or no urine, and by then very difficult to save.

Treatment hinges entirely on timing. The antidote works by occupying the enzyme that performs that conversion, giving the body a chance to excrete the parent compound harmlessly. Given within roughly three hours it is highly effective; by twelve hours the outlook is already poor; once the kidneys have failed, survival usually depends on access to dialysis.

For owners, the practical message is short. Keep antifreeze and screenwash locked away, clean up every drip, fix radiator leaks, and switch to propylene glycol products where you can. And if there is any chance at all that a cat has encountered antifreeze, go to a vet at once — this is one of the few situations where arriving 'too early' with a healthy-seeming cat is exactly the right thing to do.