Treating and Preventing Antifreeze Poisoning in Pets
Posted Nov 15 2012 6:00am
Yesterday we talked about the pathophysiology of antifreeze poisoning in pets. Today let’s touch upon what can be done to treat and prevent it.
If you ever suspect that your dog or cat could have gotten into antifreeze, get to the veterinary clinic IMMEDIATELY. Medications and procedures that prevent the absorption of ethylene glycol (e.g., induction of vomiting and administering activated charcoal) can help, but since EG is absorbed so rapidly it is usually impossible to ensure that none of the toxin makes it into the blood stream. Intravenous fluid therapy will be started to restore or maintain hydration, correct electrolyte imbalances, and promote kidney function and the excretion of ethylene glycol and its metabolites. Bicarbonate is often added to the fluids to counteract excess levels of acid within the body. A urinary catheter and closed collection system should also be put in place so urine production can be closely monitored. If it begins to decline, medications (e.g., mannitol) can be given to stimulate it.
Ethylene glycol "antidotes" must be given to pets within eight hours of the poisoning to be effective. A solution of diluted ethanol is the classic form of treatment, and is (probably) why your veterinarian has a bottle on the pharmacy shelf. It works by competing with one of the enzymes that converts EG into its toxic metabolites so that more EG can be eliminated unchanged from the body. Ethanol is the best way to treat cats that have gotten into antifreeze and is significantly cheaper (and more readily available) than fomepizole, the commonly used alternative in dogs. The downside of ethanol treatment is that, like EG, it is a depressant and diuretic, which can further compromise the pet’s condition.
Fomepizole works in the same way as ethanol, but is easier to administer (e.g., via four intravenous boluses over thirty hours versus a constant rate infusion for 48 hrs) and does not have the side effects associated with ethylene glycol. It is quite expensive, however, and is only effective in cats if given within three hours of exposure.
When antifreeze poisoning is diagnosed after signs of renal failure are present (e.g., increased BUN and creatinine, or limited or no urine production), neither ethanol nor fomepizole treatment is helpful. In these cases, long-term dialysis (either via fluids given into and drained out of the abdominal cavity or with a hemodialysis machine) is required to give an animal’s kidneys a chance to recover from the extensive damage caused by large numbers of calcium oxalate crystals passing through. If kidney function does not improve adequately, kidney transplant or euthanasia becomes necessary.
Obviously, the best way to prevent antifreeze poisoning in pets is to eliminate their access to it, but this is often easier said than done. If you are aware that an antifreeze spill has occurred, soak it up with kitty litter, safely dispose of the mixture, and rinse the area with copious amounts of water. "Pet-friendly" antifreezes that contain a bittering agent to make the product taste bad or that are made from propylene glycol rather than ethylene glycol are available and even mandated in some states, but that certainly doesn’t mean that every car on the road is using these alternatives.
If you’re looking for another reason to keep pets indoors, within a fenced yard, or on a leash — this is it. By the time your free-roaming dogs and cats make it back to you, it may be too late to save them from the deadly effects of antifreeze poisoning.
Dr. Jennifer Coates
Image: beloved pets drink from puddles (image retouched to make clear puddle look green) by Robert Couse-Baker / via Flickr