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Antifreeze: Ethylene Glycol Poisoning

Ethylene glycol is a compound found in antifreeze. It generally has a very sweet taste, making it quite palatable for both dogs and cats. It is rapidly absorbed from the gastrointestinal tract and then metabolized by the liver enzyme alcohol dehydrogenase to form the toxic compounds: glycoaldehyde, glycolic acid, glyoxalic acid, and oxalic acid. These compounds cause severe metabolic acidosis and kidney damage.

Clinical Signs

Clinical signs are very dose-dependent. In the acute stage (30 minutes to 12 hours), clinical signs are related to the ethylene glycol’s effect on the neurological and gastrointestinal systems. These signs may include: depression, nausea, vomiting (especially green vomit!), ataxia, muscle tremors, abnormal eye movements, head tremors, increased water consumption, increased urination, and hypothermia. In some dogs, these signs can resolve after 12 hours, giving the impression that the problem has resolved.

In the late stage (36-72 hours in dogs and 12-24 hours in cats), acute kidney failure occurs. Clinical signs may include: severe lethargy, coma, seizures, anorexia, vomiting, ulceration, salivation, swollen painful kidneys, and inability to produce urine. This has the highest fatality of all poisons, especially for cats.

Minimum lethal dose:
Cats: 1.4 ml/kg
(that’s just over 1 tsp for a 10# cat!)
Dogs:4.4-6.6 ml/kg
(approx ½-1 oz for a 10# dog)

Diagnosis

A thorough history is most important, though many owners are unaware that their pet had access to ethylene glycol. A CBC and chemistry profile are generally unremarkable, though evidence of kidney failure may be present in later stages. Alterations in blood glucose, calcium, and electrolytes are possible. Calcium oxalate crystals are usually present in the urine between 3 (cats) and 6 (dogs) hours post-ingestion.

Special test kits are available to test for ethylene glycol in either serum or urine. These tests must be performed within 72 hours of ingestion (with peak results between 1-6 hours post-ingestion) to be accurate.

Treatment

If ingestion was recent (1-2 hours), vomiting is induced and activated charcoal is given to reduce further absorption of the ethylene glycol. Once past this window of time, absorption has already occurred. Supportive therapy, such as IV fluids, is also important.

The goal of specific treatment is to prevent the metabolism of ethylene glycol into the toxic metabolites.

1) 4-methylpyrazole (4-MP)[Antizole or fomepazole]: This medication inactivates alcohol dehydrogenase. This treatment is only effective in dogs and is very expensive. We would generally refer a patient to the University of Minnesota for this therapy.

2) Ethanol: This is the drug of choice in cats (or in dogs in which the more expensive 4-MP is not an option). It is given as an IV solution, but generally produces profound depression. Ethanol competes against the ethylene glycol for metabolism by the alcohol dehydrogenase.

Prevention

Antifreeze is toxic! Remember, it really only takes a few licks of antifreeze off the ground to kill a cat or a small dog. We encourage pet owners to purchase antifreeze that contains propylene glycol rather than ethylene glycol.

Some cleaning products contain ethylene glycol, but the amount that needs to be ingested of these products is quite high and toxicity is generally not seen.

If you have concerns that your pet may have ingested ethylene glycol or any product containing this ingredient, contact us immediately.

  • Content prepared by St. Francis Animal and Bird Hospital, 1227 Larpenteur Ave. West, Roseville MN. 55113