Most ethylene glycol poisonings are associated with ingestion of radiator antifreeze. All animals are susceptible, with dogs and cats being affected most often. Ethylene glycol poisoning is common because antifreeze is widely used, it has a sweet taste and small lethal dose (only 3 to 4 teaspoons in dogs, 1 to 2 teaspoons in cats), and it is often stored and disposed of improperly. Sources of ethylene glycol other than antifreeze include some heat-exchange fluids used in solar collectors and ice-rink freezing equipment and some brake and transmission fluids. Absorption through the skin from topical products that contain ethylene glycol has caused toxicity in cats.
Ethylene glycol poisoning is most common in temperate and cold climates because antifreeze is used both to decrease the freezing point and to increase the boiling point of radiator fluid. In colder climates, ethylene glycol poisoning is often seasonal, with most cases occurring in the fall, winter, and early spring.
Signs begin almost immediately and resemble alcohol (ethanol) poisoning. Dogs and cats vomit due to gastrointestinal irritation, are excessively thirsty, and pass large amounts of urine. Neurologic signs develop, including depression, stupor, and lack of coordination. As the animal becomes more depressed, it drinks less and becomes dehydrated. Dogs may appear to briefly recover from these signs about 12 hours after ingestion. Severe kidney failure usually develops between 36 and 72 hours in dogs and between 12 and 24 hours in cats. Signs include a lack of energy, loss of appetite, dehydration, vomiting, diarrhea, mouth ulcers, drooling, rapid breathing, and possibly seizures or coma. The kidneys are often swollen and painful.
Diagnosis is often difficult because signs are similar to signs in other types of central nervous system disease or trauma, gastroenteritis, pancreatitis, diabetes, and severe kidney failure due to other causes. If ingestion of ethylene glycol is not witnessed, diagnosis is usually based on a combination of history, physical examination, and laboratory data.
The prognosis worsens as more time elapses between ingestion and treatment. Treatment involves reducing further absorption of ethylene glycol by inducing vomiting or flushing the stomach (or both), followed by administration of activated charcoal and sodium sulfate within 1 to 2 hours of ingestion. Once absorption has occurred, excess fluids are given to force the excretion of ethylene glycol through increased urine production and to correct dehydration. An antidote to ethylene glycol is available for dogs, but is only effective if given before kidney failure develops. In cats, intravenous treatment with ethanol can be helpful if given early after ingestion of antifreeze. In dogs and cats with severe kidney failure, the outlook is poor.
Antifreeze should be stored securely, and old antifreeze should be discarded. Any antifreeze leaks should be cleaned up immediately. The area should then be covered with cat litter, sawdust, or another absorbent material to discourage pets from licking any small amount left on the ground.
Brands of antifreeze that contain propylene glycol instead of ethylene glycol are available. Although ingestion of propylene glycol is associated with a toxic syndrome similar to that of ethylene glycol poisoning, propylene glycol is less toxic that ethylene glycol and the outlook is usually better. Propylene glycol also does not have the sweet taste of ethylene glycol, so animals may be less attracted to it.