Tylenol Toxicity

Mindy the cat sat sluggishly on the end of the exam table. A few days ago she had seemed to just have a bit of a cold, but now she wasn’t eating or drinking, and she was just hiding under the bed all day. Coincidentally, Mrs. Green’s one year old son had had similar symptoms around the same time. One dose of children’s Tylenol had made him feel so much better so quickly that it seemed logical to Mrs. Green to see if it might help Mindy too. So far it didn’t seem to be working.

Mindy was lethargic to the point of being almost non-responsive. Her gums and the skin inside her ears had an odd brownish tinge. She was having difficulty breathing and seemed swollen around her face. It was clear that she was in critical condition, and it was becoming equally clear that we were not going to be able to save her.

If left alone, the respiratory infection would have resolved itself within a few days, but now Mindy was suffering the effects of acetominophen toxicity--the active ingredient in Tylenol, and that damage was beyond treatment.

All drugs given to any human or animal need to be processed in the body through various biochemical pathways where they are broken down and then excreted from the system. One of the main biochemical pathways that humans use to process drugs happens to be nearly absent in cats. Drugs like acetominophen that are harmlessly disassembled in a toddler’s liver can end up turning into an extremely deadly poison in a cat who cannot metabolize the compound in the same way.

As with the ingestion of any toxin, the best hope for the patient is usually to prevent as much absorption as possible. This can be accomplished by inducing vomiting and giving activated charcoal orally to bind with the substance and keep it from getting into the bloodstream. One would think that getting a cat to vomit would be a simple task since they seem to have such a propensity to do it for fun in the wee hours of the morning on the path you routinely take to the bathroom in your bare feet, but like all things feline, getting a cat to vomit on command is actually a difficult task, and almost always requires intravenous administration of drugs that only your veterinarian will have.

Within 3 hours of ingestion, acetominophen has reached its peak concentrations in a cat’s bloodstream and beyond that point there is not a lot that can be done beyond supportive care and crossed fingers that the dose was low enough to be survivable. One Tylenol tablet, however, is absolutely a lethal dose for a cat.

In a cat the acetominophen binds with hemoglobin, the molecule in red blood cells that carries oxygen to all the tissues in the body and causes it to no longer be able to do its job, so all the cells in the body begin starve for oxygen and die. It also directly destroys liver and kidney cells in massive numbers. Death may come quickly with a large dose, like a single tablet, but may take several agonizing days with smaller doses. It is rare for a cat to survive intentional dosing with Tylenol. Fortunately, cats are not as prone to eating things just for the sake of eating them like dogs are, so it is not very common for cats to take it upon themselves to ingest a pill that has fallen on the ground or to lick up drops from a child’s dose.

This metabolic quirk of cats makes it necessary to be especially careful with what kinds of medications they are given. The assumption that cats are essentially just short, furry people can have some severe consequences when owners take it upon themselves to treat their pet’s medical problems, so make sure you ask a veterinarian before assuming that if it is safe for a child it must be safe for the pet too.