Apoquel®, the brand name for oclacitinib, is a significant advancement in managing pruritus in veterinary medicine. As an FDA-approved Janus Kinase (JAK) inhibitor, it targets specific signaling pathways involved in inflammation and itch. This updated clinical perspective, drawing from extensive experience, aims to provide comprehensive insights into its efficacy, administration, and potential side effects for both dogs and cats.
Understanding Apoquel®: Mechanism and Action
Oclacitinib functions by inhibiting JAK-1 and JAK-3 signaling. This action effectively blocks the effects of key cytokines, including Interleukin-31 (IL-31), which is a primary mediator of itch. Unlike corticosteroids or antihistamines, Apoquel® offers a targeted approach to relieving pruritus. Its rapid onset of action is notable, with many dogs experiencing diminished itching within 24 hours. The antipruritic effects typically last for 12-24 hours, necessitating daily administration in most cases.
Dosing and Administration in Dogs
The recommended dosage for Apoquel® in dogs is 0.4-0.6 mg/kg every 12 hours for the first 14 days, followed by 0.4-0.6 mg/kg once daily. It is crucial to adhere to this dosage range, as exceeding it can increase the risk of immunosuppression, while lower doses may prove ineffective. While some mild cases might be managed with reduced doses, it is generally not advised to deviate significantly from the prescribed regimen.
Most dogs experience significant relief from itching within a few days of starting Apoquel®. However, the drug’s efficacy can be hampered by concurrent infections with yeast, bacteria, or mites. Zoetis reports that approximately 60% of dogs with moderate to severe atopic dermatitis achieve long-term control with once-daily dosing. In some severe cases, long-term twice-daily dosing may be considered, though this is an off-label use. Effective management of moderate to severe skin diseases often requires a multimodal approach combining Apoquel® with other therapies.
While long-term studies combining Apoquel® with other immunosuppressants like steroids and cyclosporine are limited, clinical experience suggests that short-term use of steroids at anti-inflammatory doses (0.5 mg/kg twice daily, then tapered) appears safe. If concurrent steroid use is necessary, a careful evaluation of Apoquel®’s effectiveness is warranted. Transitioning from steroids to Apoquel® does not require a slow taper due to Apoquel®’s rapid onset. However, tapering steroids is essential to prevent Addisonian crisis in pets on long-term or high-dose steroid therapy.
Apoquel® is FDA-approved for dogs older than 12 months. This age restriction is due to increased risks of demodicosis and pneumonia observed in younger dogs at higher doses in clinical trials. Clinically, Apoquel® often proves less effective in young puppies experiencing allergies.
Potential Side Effects in Dogs
While generally well-tolerated, Apoquel® can cause side effects. The product insert lists: vomiting, diarrhea, lethargy, anorexia, SQ or dermal masses, decreased leukocytes, decreased globulins, and increased cholesterol and lipase. Less common side effects observed in studies include demodicosis, neoplasia, pneumonia, bloody diarrhea, skin and ear infections, UTIs, and histiocytomas. Anecdotal reports of polydipsia, increased appetite, and aggression, similar to steroid side effects, have been noted, though a definitive link to Apoquel® is not always established.
My clinical experience, involving over 1000 dogs, indicates a low incidence of serious side effects. Bone marrow suppression, the most concerning potential issue, has been observed in approximately 1% of patients. This typically manifests as changes in bloodwork rather than outward clinical signs. Regular bloodwork monitoring (CBC/Chem) is recommended at 3 months post-initiation and annually thereafter, especially to assess for liver function and changes in leukocyte counts. Bone marrow recovery is generally rapid upon dose reduction.
Ear infections are often less effectively managed with Apoquel® compared to steroids or cyclosporine. Urinary tract infections are also sometimes observed, though their direct link to Apoquel® is questionable, as atopic dermatitis patients may be predisposed.
Weight gain has been reported in some dogs on Apoquel®, though typically less pronounced than with steroids. In rare instances, behavioral changes such as hyperactivity or manic episodes have been observed, which resolved upon discontinuation of the medication. Interestingly, some dogs have shown improved mobility and overall well-being, potentially due to reduced skin inflammation and associated discomfort.
Long-term side effects are not well-documented, but concerns include unspecified skin masses and potential exacerbation of neoplastic conditions. Histiocytomas and viral papillomas, while generally self-limiting, might be more common or persistent in dogs on Apoquel®. It is imperative to have any new masses evaluated by a veterinarian. The notion that Apoquel® directly causes cancer or death is largely unsubstantiated by current evidence; often, underlying internal diseases trigger or exacerbate skin issues.
Monitoring Protocol
For dogs on once-daily Apoquel® dosing, the monitoring protocol typically involves a baseline CBC/Chem6 before starting the medication, followed by checks at 3 months and then annually. The CBC is paramount for monitoring bone marrow suppression and overall health. Prior liver disease assessment is also important, excluding elevations caused by prior steroid use. Urine monitoring is not routinely performed but may be considered based on individual cases.
Summary of Canine Use
Apoquel® is a valuable therapeutic option for dogs with atopic dermatitis, offering rapid itch relief and a generally favorable safety profile. Key benefits include its quick action, low incidence of gastrointestinal side effects, and rare long-term adverse events. Downsides include the need for bone marrow monitoring, variable efficacy in some patients, and limited long-term data.
Apoquel® Use in Cats
Apoquel® can be used in cats for managing atopic dermatitis and other immune-mediated diseases, although this is an off-label use. Cats often require higher doses than dogs, and multiple daily administrations may be necessary. While some cats respond well, others show no improvement. Bloodwork monitoring is crucial for feline patients, typically at 2 and 5 months, and then every six months.
In a review of 166 cats, 66% achieved good control, but approximately 7% discontinued therapy within 2-5 months due to low immune cell counts (neutropenia). Apoquel® was ineffective in 34% of cats. Other reported issues included refusal to take the medication, vomiting, diarrhea, and lethargy. Due to the potential for off-label side effects, management of feline cases requiring Apoquel® is best handled by a veterinary dermatologist.
References
- Zoetis. (n.d.). Apoquel® Prescribing Information. Retrieved from drug insert
- U.S. Food & Drug Administration. (n.d.). How to Report Animal Drug and Device Side Effects and Product Problems. Retrieved from FDA report