By Dr. David Gross

This is one of the most common forms of poisoning seen in dogs and cats. It usually happens when the antifreeze drips from your vehicle’s radiator, forming a puddle on the garage floor or driveway. The active ingredient in antifreeze is ethylene glycol, a syrupy liquid that seems almost addictive to some pets.

You must take special care if you change your antifreeze yourself, since pets can get into containers left open or spilled. It is possible for a cat to poison itself by walking through a puddle then licking its paws. As little as five tablespoons of commercial antifreeze is enough to kill a medium-sized dog. If you see or suspect your pet has ingested antifreeze, you should make it vomit, by giving it a teaspoonful of hydrogen peroxide per five pounds of body weight, but not more than three teaspoonfuls at a time. If it vomits or not, take it to your veterinarian as quickly as possible and explain what you think has happened. If your pet has already vomited, do not try to make it vomit more. Do not try to induce vomiting if the pet is showing signs of distress, shock, difficult breathing or is unconscious.

Ethylene glycol is also an ingredient in some liquid rust-inhibitors, incorporated in solar collectors, used in many chemical manufacturing processes and can also be found in a variety of household products. Check the labels! To be most effective, your veterinarian must administer treatment within three to eight hours. Ethylene glycol is actually an alcohol converted by enzymes in the liver, particularly alcohol dehydrogenase, into oxalic acid. The oxalic acid combines with calcium in the blood to form calcium oxalate crystals that block the nephrons in the kidneys and result in kidney failure.

Since ethylene glycol is an alcohol, the early signs of poisoning resemble drunkenness; euphoria and/or delirium, wobbly gait, uncoordinated movements, nausea as evidenced by excessive salivation, lip smacking, dry heaving and vomiting. This phase can persist for about six hours and the animal may appear to be better — not so! If untreated the signs progress to excessive urination, diarrhea, rapid heart rate, depression, weakness and eventually into fainting, tremors, convulsive seizures, and coma, all signs of kidney failure.

If you arrive at the animal hospital in time and give a history of your pet ingesting antifreeze, or your veterinarian runs appropriate tests and makes the diagnosis, before signs of kidney failure occur, there is a good chance your pet will be saved. Treatment involves the induction of vomiting. Using activated charcoal to bind any ethylene glycol still in the digestive tract is not effective, but may be indicated when other toxins are suspected. Since 1996, your veterinarian has had access to fomepizole (Antizol-Vet).

This drug is an effective antidote, if administered intravenously before kidney damage occurs. Back in the olden days, we used grain alcohol as an antidote, significantly less expensive than fomepizole. Alcohol dehydrogenase has about 100 times the affinity for grain alcohol than it does for ethylene glycol. When used as an antidote, the liver metabolizes less ethylene glycol and fewer oxalate crystals form. Depending upon the severity of kidney damage, it still might be possible to save your pet with aggressive fluid therapy to flush the kidneys, and other supportive treatment. Some specialty practices may be equipped to provide kidney (renal) dialysis. You do not want to know how much a kidney transplant will cost, but it is possible in both dogs and cats, in specialized centers with the necessary equipment and experience.

D. R. Gross graduated from Colorado State University’s veterinary school in 1960 and was in private practice for ten years. He enrolled in graduate school at Ohio State University earning a M.Sc. degree in 1972 and a Ph.D. degree in 1974. He retired in 2006 as Professor and Head of Veterinary Biosciences, at the University of Illinois, Urbana-Champaign. Dr. Gross is a Fellow of the Cardiovascular Section of the American Physiological Society. During his academic career, he published over 90 papers in refereed scientific journals and over 100 abstracts in proceedings of scientific meetings.