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Antifreeze Poisoning in Pets

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Many household items are potentially toxic to pets (see also poison).  Antifreeze is among the most problematic poisons for a variety of reasons:

  • Antifreeze is commonly changed by do-it-yourself mechanics who may allow the coolant to drain into the street where pets can drink it.
  • Antifreeze has a sweet taste that pets like.
  • Antifreeze is a potent poison that can cause kidney problems and even death.

In northern climates, antifreeze poisonings are most common around those times when automotive coolant is changed: typically fall, winter, and early spring.  

Automotive coolants typically contain the chemical ethylene glycol.  This chemical is similar in structure to alcohol, so that signs of intoxication are similar to those of drunkenness.  Poisoned dogs or cats may vomit and show nervous system signs, such as staggering and tiredness.  They tend to drink and urinate large amounts.  Within a few hours of ingestion, byproducts of ethylene glycol produce crystals that cause kidney damage as the body tries to remove them.  Kidney damage can be severe and life-threatening, even after ingestion of only a few teaspoons of antifreeze.  

Treatment for antifreeze poisoning needs to be instituted as soon as possible, so you should take your pet to the veterinarian immediately if you suspect that it has drunken antifreeze.  Treatment is often begun based on suspicion of antifreeze poisoning, without being able to confirm it.  Your vet may perform a blood test for ethylene glycol, but this is only effective when a fairly large amount has been consumed.  Your vet may also check the urine with an ultraviolet light, because some types of antifreeze fluoresce, although this test is not always accurate.  Blood and urine tests are needed to monitor the status of the kidneys, as well as to look for suspicious crystals in the urine.

If anitfreeze poisoning occurred within the past few hours, the vet may induce vomiting or flush the stomach in an attempt to remove unabsorbed coolant.  Intravenous fluids are given to keep your pet well hydrated and to flush the kidneys.  A special drug can be injected to decrease the formation of crystals, thereby sparing the kidneys from serious damage.  This drug is ineffective in cats, so alcohol is used instead.  Alcohol competes with the ethylene glycol for metabolism, thereby decreasing the production of crystals.  These treatments are most effective if given within a few hours of ingestion, before serious kidney damage has occurred.  



What is antifreeze?

Antifreeze is the automotive coolant used in the radiator of your car.  Most brands contain ethylene glycol, which is a potent poison.

Is antifreeze poisoning common in pets?

Yes, especially around the times of the year when auto coolant is typically changed (eg, fall, winter, and early spring).  Backyard mechanics sometimes pour the old antifreeze in the gutter, where pets drink it because of its sweet taste.  

How does antifreeze harm a pet?

The ethylene glycol in antifreeze is converted to crystals that severely damage the kidney.  

What should I do if I see my pet drinking antifreeze?

Rush your pet to a veterinarian immediately!  The vet can give your pet fluids and other medications to prevent kidney damage.

Credit: Written and reviewed by John A. Bukowski, DVM, MPH, PhDand Susan E. Aiello, DVM, ELS
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