Chemical in some medications toxic to felines

A cat surrendered at Espanola Humane recently almost died of “mysterious” symptoms until a quick-thinking veterinarian cracked the case – wrongly prescribed flea-and-tick medication.

The shelter’s veterinarian examined the orange tabby after he was described as having symptoms of twitching, drooling, muscle tremors, “drunk walking,” and agitation. She could find no reason for his condition except a thin streak of oily fur on his back.

As suspected, the oily substance was a spot-on topical flea-and-tick medication formulated for dogs only, containing permethrin, a chemical toxic to cats.

The cat, named Pete, was suffering from chemical poisoning and without emergency treatment likely would have died. The veterinarian immediately shaved a wide stripe around the affected area, bathed him, gave him IV fluids and activated charcoal and other medications.

Pete made a full recovery and has since found a new home.

Unfortunately, it’s a common but unfortunate mistake for many pet owners as they seek to protect their pets from fleas and ticks but are too quick to buy medication. Topical insecticides are one of the top feline toxins reported to the Pet Poison Helpline. It’s a highly concentrated treatment specifically formulated for dogs and toxic to cats. It’s safe for canines but felines have a liver that can’t metabolize pyrethroids.

Common chemical names for pyrethroids include: permethrin, allethrin, deltamethrin, cypermethrin, and cyphenothrin. In addition to having highly toxic concentrations, these topical medications for dogs are in an oily base so the spot-on treatment will get down onto the skin and spread over the entire body — which also means it’s very difficult to wash off, and it’s meant to last. Another class of chemicals that can be found in flea and tick treatments for dogs are organophosphates, which are also toxic to cats, and are used in dog flea collars and dips.

The veterinarian said it’s important that any medications used on felines are specifically formulated for cats. If you accidentally applied dog-only flea and tick medication to your cat, immediately bathe your cat with dish soap (regular shampoo will not remove this oily substance) and contact your veterinarian, an emergency veterinarian, or an animal poison control center.

For more information, visit ASPCA’s Animal Poison Control: