Antifreeze Poisoning in Dogs

Pug on pavement.

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Many dog owners know that antifreeze is toxic to dogs, but not all people understand how dangerous antifreeze poisoning can really be. Unfortunately, exposure to even a small amount of antifreeze can quickly lead to death. Antifreeze poisoning in dogs is a very serious matter.

Antifreeze is a common hazard during winter, but dogs can easily be exposed to it any time of year. Dogs are most likely to be poisoned if they ingest it (though it technically can be absorbed through the skin). It is believed that dogs are attracted to antifreeze because it has a sweet taste. A dog may find antifreeze in storage areas but is not uncommon to find small puddles of it in driveways, garages, and roadways. Be wary of puddles that have a greenish color or iridescent haze.

Some types of antifreeze are more toxic than others. Most brands contain the active ingredient ethylene glycol, which is also the most toxic. Antifreeze with the active ingredient propylene glycol or methanol is still toxic, but less so.

It takes very little ethylene glycol to poison a dog. Here is a breakdown of the toxic doses:

Toxic Doses of Ethylene Glycol in Dogs

(amounts are approximate)

 Dog's weight (lbs)  Toxic Dose (tbsp)
10                1-2
20                2-3
40                5
60                8
80                10-11

The Merck Veterinary Manual states: "The minimum lethal dose of undiluted EG is 1.4 mL/kg body wt in cats, 4.4 mL/kg in dogs, 7–8 mL/kg in poultry, and 2–10 mL/kg in cattle. Younger animals may be more susceptible."

Signs of Ethylene Glycol Poisoning

After exposure to ethylene glycol, most dogs begin showing signs very quickly. At first, the signs may resemble alcohol intoxication. For the first 30 minutes to 12 hours after exposure, dogs often exhibit the following signs: 

  • Vomiting (due to GI irritation)
  • Lethargy
  • Drunkenness/ataxia/trouble walking
  • Increased thirst and/or urination
  • Excessive salivation
  • Sedation or stupor

After the first 12 hours, the above signs tend to subside. This may lead one to think the dog is improving. However, the toxin continues to do serious damage to the internal organs. 

Somewhere between 36 and 72 hours after intoxication, the dog's kidneys will begin to fail. At this point, the dog will again show signs of illness such as the following:

  • Lethargy
  • Loss of appetite
  • Vomiting
  • Diarrhea
  • Bad breath
  • Seizures

If aggressive veterinary treatment has not begun before this final stage, the chances of survival are significantly decreased.

What To Do If Your Dog Gets Into Antifreeze

Unfortunately, ethylene glycol poisoning often leads to death. The sooner it can be detected and treated, the better the chance the dog has for recovery. If you suspect your dog has been exposed to antifreeze, contact your veterinarian immediately. The best thing you can do is to head straight to the nearest open veterinarian. If it's after hours, find an emergency clinic near you.

DO NOT induce vomiting unless your vet instructs you to do so. Do not just wait for your dog to show improvement. Without treatment, dogs who have been poisoned by antifreeze will almost certainly suffer kidney failure followed by death. Time is of the essence in order to prevent death.

Diagnosing Antifreeze Poisoning

If you suspect your dog has been exposed to antifreeze, but are not sure, your veterinarian will look at your dog's history, physical examination, and laboratory data together to make a diagnosis. If you know for sure your dog was exposed to antifreeze, your vet will still need to run several tests. At the very least, the vet will perform blood work to assess organ function and cell counts. A urinalysis will also be done to look for abnormalities (such as calcium oxalate crystals, which are often seen after ethylene glycol poisoning).

Once the vet can determine the extent of damage done so far and the state of the dog, a treatment plan will be developed.

Treating Dogs for Antifreeze Poisoning

If ethylene glycol poisoning is detected early enough (within 8-12 hours of exposure), the first goal of treatment is to prevent further metabolism of the ethylene glycol. This is done by administering either the drug fomepizole (also known as 4-MP) or ethanol (also known as ethyl alcohol, which is drinking alcohol).

Because 4-MP is expensive, not all vets will have it on hand. Therefore, ethanol is commonly used in the form of grain alcohol or even vodka. It is important to know that alcohol is normally toxic to pets. However, when given carefully and properly by a vet to treat antifreeze poisoning, it interferes with the absorption of ethylene glycol.

The next step in treatment involves intensive supportive care. IV fluids are administered to keep the dog hydrated and correct electrolyte imbalances. Medications are given to treat symptoms. The dog's vitals are closely monitored and lab work is checked often in order to measure recovery.

Unfortunately, not all dogs will survive ethylene glycol poisoning, even with aggressive treatment. The sooner you can get the affected dog to the vet, the better chance there is of survival.

Protecting Your Dog From Antifreeze

The best thing you can do now is to keep your dog from exposure to ethylene glycol. In addition to antifreeze, this chemical can be found in brake fluid, de-icers, certain cleaners and other household or automotive solutions. Store all chemicals out of reach of your dog and clean up any spills immediately. Consider changing to a less toxic form of antifreeze (one that contains propylene glycol or methanol). Use caution when walking with your dog. Keep your dog from stepping in or drinking from puddles with unknown liquids. Never let your dog roam free because you never know what he may be exposed to.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.