Antifreeze Poisoning

Toxin exposures or accidental poisonings are some of the most common things we handle at the hospital. We’ve dealt with chocolate ingestion, jewelry ingestion, pesticides, cleaning products, mushrooms, illegal drugs, prescription drugs, and automotive chemicals. (Dogs will eat almost anything, which gets them in a -lot- of trouble.) I’m going to review antifreeze poisoning this week.

Antifreeze usually contains a chemical called ethylene glycol. Ethylene glycol tastes sweet, which is what attracts animals (dogs and cats both) to drink it. About 1/2 teaspoon of liquid per pound of a dog’s body weight is a lethal dose. Cats have a lethal dose at 1/8 teaspoon per pound of body weight.

The first signs of the toxicity start 30 minutes to 12 hours after ingesting ethylene glycol. Animals may appear drunk (wobbly on their feet, weakness of the legs), sedated, sleepy, or even have seizures or go into a coma. Pets will also drink a large amount of water and urinate a large amount, too. Sometimes owners are not around to witness this stage and are unaware that their pet has something seriously wrong happening.

The liver processes ethylene glycol into several toxic chemicals in the body. These chemicals cause the body to become too acidic. Animals may have rapid breathing and/or rapid heart rate. These signs can occur 12 to 24 hours after ingestion.

Some of the chemical byproducts combine with calcium to form crystals in the kidneys. The crystals are so damaging to the kidneys that animals go into sudden (acute) renal failure. They may be seriously lethargic, have vomiting or lack of appetite. In some cases, the kidneys can completely shut down. The pictures below show two forms of the crystal.


We can detect ethylene glycol toxicity by seeing the crystals in the urine, by recognizing kidney damage on bloodwork results, or if the owner knows the pet ingested ethylene glycol. There is a test kit that can be used, but only if it’s less than 12 hours after the ethylene glycol was ingested. Also, an animal’s mouth, stomach contents, or urine may glow under a backlight.

If we can start treatment before the toxic byproducts are produced in the body, we stand a much better chance of saving a pet. Once kidney damage has happened, it’s very unlikely that we will be able to return the kidneys to normal function. Some animals may survive for a time with damaged kidneys, but the prognosis is terrible if more than 8 hours have gone by since ingestion of the ethylene glycol.

There are antidotes for ethylene glycol. Fomepizole and 4-methylpyrazole are very useful if given soon enough. Some pets can be treated as outpatients this way.

One of the other ways to treat ethylene glycol toxicity is to hospitalize the pet and give ethanol intravenously. Yup, ethanol — grain alcohol — which is found in all of the alcohols we consume recreationally. Vodka is generally used for this purpose because it’s relatively ‘clean’ compared to other types of alcohol. Animals treated with ethanol have to be kept in the hospital to make sure that they don’t have any trouble with the high amount of alcohol that has to be put into their system to treat the toxicity.

The best way to handle ethylene glycol toxicity is to prevent your pet from coming into contact with it in the first place. Keep all automotive products carefully stored out of reach, and be sure to clean up any spills in the garage or the driveway.



Filed under toxicology

4 responses to “Antifreeze Poisoning

  1. Chris

    This is so scary! We have high shelves in the garage for storage of these kinds of things…whew!

  2. Val Lewis

    Good post, valuable information.

  3. Toxins are a tough sort of case for us and often have bad outcomes. Keeping pets away from exposure is the best way to handle them.

  4. Thanks! I’m trying to get more practical info on the blog.

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