Antifreeze Toxicity


by Dr Francesca Brown

Ethylene glycol in Antifreeze is extremely toxic.

Less common in New Zealand as a poison than in places like the United States.

However, in my years of practice I have seen at least 4 confirmed and other suspected cases when I practised in Dunedin, where the use of antifreeze is perhaps more common, due to the student population, meaning there is a larger number of older cars.



Ethylene glycol is added (as antifreeze) to radiators to reduce the freezing point. Its use is more common in colder climates and older cars, and it is in this form that poisoning is most commonly attributed. Antifreeze may also be added to toilets to prevent them freezing. In really cold climates, water with antifreeze may be the only sources of unfrozen water.


 Image source wikimedia commons

There are other uses for ethylene glycol in the manufacture of detergents, paints, lacquers, resin, some pharmaceuticals, polishes, plastics, cosmetics, colour film processing and inks (including those used in ball point pens).


Why do animals drink it?

Colourless, odourless and very palatable because it is sweet. And as mentioned above, in some places it may be the only unfrozen water available.


What happens in the body?

It is absorbed from the gastrointestinal tract very quickly, with peak levels occurring within 1 - 3 hours. One of the break down products of ethylene glycol readily binds to tissues inside the kidneys, resulting in kidney failure. Cats, due to the way they metabolise ethylene glycol, are the most at risk from the toxic effects, however it is considered a very toxic substance for all species, with a very high mortality (or death) rate.


Signs you might see?

Some signs include vomiting, nausea, difficulty walking, seizures, coma, fast heart rates and breathing and signs of fluid retention (because the kidneys may stop functioning all together). These depend on how much was ingested. Death can result quickly when a lot has been ingested, otherwise signs may be milder and progress through to renal failure.

If you suspect your pet may have had access to ethylene glycol, do not delay.  Get them to your veterinarian immediately.



Although there is a lot more to it, in summary treatment revolves around:
  • Removing any agent from the stomach if it has just been ingested.
  • Controlling neurological signs such as seizures with anti-seizure medications
  • Administration of ethanol (pure alcohol) in strictly measured amounts (do not try this at home) to displace ethylene glycol from the enzyme which breaks it down to the dangerous metabolites. Ethanol too is toxic, but nowhere near as lethal in the short term as ethylene glycol. 
  • Treatment is intensive and can be costly. The outcome is by no means guaranteed.



Avoid leaving antifreeze anywhere that your pet or other people may access.

If you are using antifreeze in your car, when you drain the radiator, drain it into a container and dispose of it safely. Do not let it run down the drain. All pets, but cats in particular, tend to lick liquid in the contaminated drains and will be poisoned as a result. They are drawn to its sweet taste.

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