Last reviewed on November 10, 2015


Winter has so far been relatively mild in my part of the world. However, that does not mean that winter hazards do not still exist for your pet. Antifreeze is one such hazard.


Antifreeze is toxic for both dogs and cats. The toxicity is dose related and even a very small amount of antifreeze can be lethal for a small pet such as your cat. For the average cat, as little as one teaspoon of antifreeze can be lethal. To make matters even worse, antifreeze apparently has a sweet flavor that actually attracts many animals.


Antifreeze contains ethylene glycol, which is the toxic compound in the substance. Ethylene glycol can also be found in several other automotive products (windshield fluid, motor oil, brake fluid, etc.), as well as in some paints and solvents.


Symptoms of antifreeze poisoning in cats will initially resemble alcohol toxicity. Signs will include drunken behavior such as incoordination and drooling. Vomiting can occur. Seizures may also be seen. Your cat may seem thirsty as well and may urinate more than normal.


After this initial phase, your cat may appear to improve for a short time. However, during this time, the chemical is still damaging your cat’s kidneys. Within a day or less, your cat will begin to experience symptoms of acute kidney failure. Lack of appetite, depression, vomiting, seizures, coma and eventually death will be the result.


Immediate veterinary intervention is critical in saving a cat that has ingested antifreeze. The sooner treatment is initiated, the greater the chance of survival. Fomepizole (or 4-MP) is one potential antidote for ethylene glycol poisoning and is used reasonably successfully in dogs if administered within 8 hours of ingestion. However, in cats, treatment with fomepizole must be started within three hours of ingestion in order to be effective. Ethanol may be used as an antidote as well. For cats, treatment with ethanol must be started within eight hours of ingestion. Ethanol treatment does have side effects of its own, including enhancing the central nervous system depression caused by the ethylene glycol itself.


Even with the fomepizole or ethanol treatments, supportive treatment will likely be necessary for your cat as well. Fluid administration is usually recommended concurrent with fomepizole or ethanol treatment. Acidosis may be severe as a result of the toxicity and may need to be treated as well.


Once kidney damage has occurred, the likelihood of a successful treatment for your cat is much lower. When fomepizole or ethanol treatment is not initiated within a few hours of ingestion, even more aggressive treatment, including hemodialysis, will be necessary to try to save your cat. Even so, many cats do not survive.


Protect your cat from antifreeze or ethylene glycol poisoning by storing substances that contain ethylene glycol in a secure location that your cat cannot access. If antifreeze is spilled, clean up the spill immediately and check your vehicles regularly for signs of leaks.


If you know or suspect that your cat has ingested antifreeze or another substance containing ethylene glycol, seek veterinary care immediately. Do not wait to see if your cat gets sick. By then, it will likely be too late to save your cat.



Dr. Lorie Huston



Image: berna namoglu / via Shutterstock