July 2025

In this VETgirl online veterinary continuing education blog, ASPCA® Poison Control provides us with a critical update to increase awareness of reports of severe Apoquel® (oclacitinib) toxicosis in dogs and cats during overdose situations. The research was based on retrospective data that was voluntarily reported to a toxicology specialty consultation service, Poison Control, based out of Champaign, IL. Continue reading to recognize the clinical signs and current recommendations!

Oclacitinib Toxicosis in Dogs and Cats

By ASPCA® Poison Control

Oclacitinib, otherwise more commonly known as Apoquel®, is a Janus kinase inhibitor (e.g., JAK inhibitor) approved for use in dogs at 0.4-0.6 mg/kg PO to control pruritus secondary to allergic dermatitis and to control atopic dermatitis in dogs at least 12 months of age. It is used at similar dosages empirically for a variety of other conditions in dogs, and its use has been suggested off-label in cats at dosages up to 1 mg/kg for dermal indications. Initially, reports of acute toxicosis were limited to gastrointestinal (GI) signs (e.g., vomiting, diarrhea). However, with the introduction of the chewable formulation, additional reports of systemic toxicosis started to occur, likely with larger amounts being ingested due to the palatability.

Recently, Lister et al. published a brief communication in the Journal of Veterinary Emergency and Critical Care to increase awareness of  reports of severe oclacitinib toxicosis in dogs and cats, some resulting in death or euthanasia due to poor prognosis.1 The research was based on retrospective data that was voluntarily reported to a toxicology specialty consultation service, Poison Control, based out of Champaign, IL.

The unflavored tablet oclacitinib formulation was approved for use in the United States in 2013 and a highly palatable chewable formulation was released June 2023. The increase in palatability is supported by a palatability study stating that there was 89.9-93.3% acceptance of the new chewable formulation.1 Prior to the introduction of the chewable formulation, one-time exposures to oclacitinib were generally expected to cause mild clinical signs, with vomiting, diarrhea, and mild lethargy being the most common clinical signs reported. However, the increased palatability of the chewable formulation seems to have resulted in an increase of reported exposures and larger dosage exposures. In fact, this is supported by the palatability study as one of the study participants was withdrawn from the study after she and potentially her housemate ingested the contents of bottle of with 50 oclacitinib chewable tablets after gaining access to the location that the tablets were stored.2

With the increased frequency and dosage of the exposures, additional severe and potentially life-threatening systemic signs are being reported with oclacitinib toxicity.

Small ingestions of oclacitinib (e.g., < 10 mg/kg) can still be monitored at home and treated supportively. However, the authors recommend more aggressive treatment for dogs and cats ingesting dosages of oclacitinib of 10 mg/kg or more and those showing clinical signs beyond mild gastrointestinal upset.

Pet owners or veterinary professionals are encouraged to call ASPCA® Poison Control if a dog or a cat ingests more than a therapeutic dosage for the most up to date information on management and prognostic information with oclacitinib toxicosis. Veterinarians should also report these events both to the manufacturer using the information printed on the bottle and the FDA either online at https://www.fda.gov/animal-veterinary/report-problem/how-report-animal-drug-and-device-side-effects-and-product-problems or by calling 1-888-FDA-VETS (1-888-332-8387).

References:

  1. Lister S, Basile JK, Wegenast C. Oclacitinib Intoxication. JVECC (San Antonio). Published online April 20, 2025; Accessed May 2025; https://onlinelibrary.wiley.com/doi/epdf/10.1111/vec.13459
  2. Visser M, Walsh K, King V, et al. Acceptance of oclacitinib maleate (Apoquel®) chewable tablets in client-owned dogs with allergic and atopic dermatitis. BMC Vet Res. 2022;18(1):103.

The ASPCA® is the #1 expert in animal toxicology, delivering the most accurate, up-to-date advice, uniquely tailored to meet the needs of pets and their parents. By bringing the right care to each case, the ASPCA® Poison Control is always the right call.


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