CORRECTION: This story has been updated to say that too much of the drug can cause kidney injuries in cats. What quantity constitutes “harmful” is currently unknown.

The NC State College of Veterinary Medicine has treated two cats that developed acute kidney injury after eating chewable Apoquel —  used to treat itching and inflammation associated with allergic dermatitis — prescribed to dogs also living in their households. 

Dr. Tyler Johnson, a fellow in advanced emergency and critical care and extracorporeal therapies at the NC State Veterinary Hospital, says both cats required hemodialysis for support but fully recovered after in-clinic care.

“Previous reports of very high ingestions like this have resulted in death,” he says. “The incidence of Apoquel ingestion-related toxicity has increased at our hospital since the release of a chewable formulation that, for some reason, cats seem to be inclined to eat. Both of the cats we treated actively sought out the medication.”

Dr. Shelly Vaden, professor of small animal internal medicine at the NC State College of Veterinary Medicine and president of the American College of Veterinary Nephrology and Urology, says families living with both cats and dogs should be aware that Apoquel is dangerous to cats.

“We’re hoping veterinarians start asking whether there are cats in the household before prescribing the chewable form,” says Vaden, also president of the International Renal Interest Society. “We believe that households with cats should rely on the original, nonchewable form of Apoquel or be extra diligent in keeping the chewable form away from their cats.”

In cats, too many of the pork liver-flavored chewable tablets can cause severe clinical signs, including lethargy, vomiting, diarrhea, facial swelling, liver damage and kidney injury. Some affected cats may require intensive care hospitalization, and those with severe kidney injury may need treatment with hemodialysis, Vaden says.

NC State is the only veterinary facility between Washington, D.C., and Florida that offers all types of extracorporeal therapy such as hemodialysis, hemoperfusion or therapeutic plasma exchange to help rid an animal of toxins or other harmful substances in the bloodstream.

No studies of how well or even whether these procedures remove Apoquel from the bloodstream have been performed, but Johnson is writing a case study of the two treatments for publication, the first step leading to clinical studies and an official treatment protocol.

“The scientific literature is very sparse,” he says. “We talked to poison control centers to see what they have amassed, and they will follow up with some of these cases to understand what happened to them. That’s where a lot of the information is coming from right now. Our case study demonstrates, at least for two animals that were severely affected, how we can successfully support them through it.”

One possibility is that the extracorporeal therapy simply supports the kidneys long enough for the body to rid itself of the toxins. Both cats treated at the NC State Veterinary Hospital recovered fully after four dialysis treatments, Johnson says.

“I don’t think that our treatments for either of these cats did anything to remove the medication that they ingested, but what it did do is support their injury well enough that they were able to have a pretty quick recovery,” he says. “What we essentially did with dialysis was intervene for the kidneys that weren’t functioning well and allow time for those kidneys to recover enough to heal themselves.”

If a cat ingests Apoquel chewable tablets, owners should seek immediate veterinary attention. Decontamination procedures such as inducing vomiting and administering charcoal can be administered, but extracorporeal therapies may be required in cases of large ingestions. 

Cheese was the first cat treated at NC State for Apoquel toxicity. He had received the decontamination procedures at his local veterinarian but was referred to NC State when he remained very ill. 

“In the future as an older cat, he might have kidney disease, but right now it’s like nothing ever happened,” Johnson says. “Everything is cool and good. Things are great even.”

Cheese the cat ingested Apoquel and required hemodialysis at the NC State Veterinary Hospital to help his kidneys heal. Photo courtesy of Dr. Tyler Johnson with permission from owners