From The Vet: 6 Human Medications That Can Be Deadly For Cats If Eaten



Vets hear every day about human medications that cats have ingested at home. While many are a result of accidental access, some owners offer them to their feline hoping for the the same result we get – pain relief, etc. It is important to remember that not only is a cat’s metabolism profoundly different than ours, they are much smaller than even a very small child. Here is a breakdown of the most common medications cats have access to that should be completely avoided:


By now, most people know that Tylenol (acetaminophen) will KILL cats. Because cats cannot metabolize acetaminophen, it builds up in the blood. It then grabs onto the surface of your cat’s red blood cells in the spots normally used to carry oxygen to the tissues. Cats given Tylenol die a slow and painful death as their cells slowly suffocate. This drug is an absolute NEVER drug for cats.


This is a first choice among humans to manage everything from headaches to joint pain. Cats are more sensitive to the side effects from this class of medications and they will cause vomiting, diarrhea, gastric erosion and even damage to the kidneys. There is never going to be a case where you should medicate your cat at home with Ibuprofen.

Benadryl® (diphenhydramine)

For a long time, it seemed like every caller was directed to try giving Benadryl to their pet. It became a panacea to help a Pandora’s box of symptoms from itching to insomnia. Although diphenhydramine is generally considered safe, it might not do much for your cat except make her sleepy (and cannot be consistently expected to even do that). Studies in humans have suggested that older antihistamines may contribute to dementia¹. Even readily available drugs are still drugs and none are completely without side effects. Let your vet help you address whatever symptom you may be trying to treat with a medication that is proven to be safe and effective.

Visine® eye drops

Some cats experience itchy red eyes from allergic disease and other causes. Owners are used to reaching for the Visine for their own eyes, but do not be tempted to apply Visine to your cat’s eyes. Visine is Tetrahydrozoline HCl and it works by constricting the blood vessels in the eye. Although constricting blood vessels will visibly reduce ocular redness, you will have done nothing to address the reason for the redness. Serious ocular problems like corneal injury can cause red eyes in cats and since you cannot ask him if he has pain, so it is best not to mask issues with a medication that has not been tested for use in animal patients.


Cats do vomit sometimes and you might be tempted to grab the Pepto.  Don’t do it.  Pepto Bismol or bismuth subsalicylate is in the same family as aspirin (acetylsalicylic acid) which can cause some of the same issues from cats that Ibuprofen can. We all think of the good ole pink liquid as safe and have memories of taking it as children and beyond, but it is not safe for cats. If your cat vomits more than once in a row or more frequently than once weekly, you should ask you vet.

Be aware of children’s cough or cold medication syrups. Some of these medications have artificial sweeteners that could be very toxic to pets. Avoid these unless your vet has given you specific instructions for which and what dose.

Cats are not small humans or even small dogs, even though they may act like it sometimes.  Do not be tempted to try to manage issues with at-home medications. Sometimes you can harm your cat or even complicate what your vet can give to help if you have administered these drugs at home before calling him/her. Keep your cat safe. Give her cat tested medications appropriately chosen and dosed by your vet.


  1. Psychosomatics. 1994 Jul-Aug;35(4):399-402. Diphenhydramine-induced delirium in elderly hospitalized patients with mild dementia. Tejera CA, Saravay SM, Goldman E, Gluck L.


Written by Dr. Kathryn Primm
Story Page

Would you donate 10 seconds of your time to help shelter cats?


Signup for Our Newsletter, and We'll Donate 1 Meal to a Shelter Cat In Need!

Because we believe all cats matter, we created an email newsletter that’s packed with health & training tips, safety info, and products that support animal shelters. Can we send it to you?

Thank you for signing up!