Zenrelia for Dogs (Ilunocitinib)

PetMD’s medications content was written and reviewed by veterinary professionals to answer your most common questions about how medications function, their side effects, and what species they are prescribed for. This content shouldn’t take the place of advice by your vet.

What Is Zenrelia Used for in Dogs?

Zenrelia (active ingredient ilunocitinib) is a prescription veterinary medication used to reduce the itching and inflammation of your dog’s skin that is caused by allergies. 

Veterinarians prescribe Zenrelia short-term for allergic flare-ups or long-term for the management of skin issues triggered by allergies. 

Available for dogs at least 12 months of age as an oral unflavored hypoallergenic tablet, Zenrelia starts working rapidly to relieve itching. 

While Zenrelia does not cure your dog’s underlying allergic skin disease, it is an effective treatment to relieve the itching and redness triggered by it. 

Zenrelia may be used as a sole medication but is often combined with other allergy management treatments to improve your dog’s skin health, including flea and tick preventative, medicated shampoo therapy, medicated spray, mousse, wipes, omega fatty acid supplements, and therapeutic hypoallergenic diets. 

It can take time and patience to partner with your vet to determine the treatment that works best for your allergic dog. 

Is Zenrelia FDA-Approved? 

Yes, Zenrelia is approved by the U.S. Food and Drug Administration (FDA) for use in dogs at least 12 months old to control pruritus (itching) associated with allergic dermatitis and to control atopic dermatitis. 

Allergic dermatitis is an umbrella term that describes skin conditions in dogs that lead to itching and inflammation due to allergic responses. According to the manufacturer, this includes a range of conditions such as: 

• Atopic dermatitis: A common long-term skin condition triggered by environmental allergens such as pollen, dust, mold, and grass, among others 

• Ectoparasite hypersensitivity: Which includes flea allergy dermatitis and sarcoptic mange 

• Food allergy dermatitis: A skin reaction caused by an immune response to certain proteins in a dog’s diet 

• Contact dermatitis: A skin reaction that occurs when a dog’s skin comes into direct contact with an irritant, such as certain plants, chemicals, or fabrics 

Speak with your veterinarian about whether Zenrelia is right for your dog. 

Zenrelia Considerations for Dogs

• Zenrelia should not be used in puppies less than 12 months of age or in dogs with a serious infection. 

• Dogs should be up to date on vaccinations before starting Zenrelia, and dogs on Zenrelia should not receive any vaccines.

  • Discontinue Zenrelia for at least 28 days to three months prior to vaccination and withhold Zenrelia for at least 28 days after vaccination. 

  • Discuss your dog’s vaccine schedule with your veterinarian. 

• At the time of this publication, Zenrelia had not yet been evaluated in breeding, pregnant, or lactating dogs and had not been evaluated in combination with other immune suppressive medications such as glucocorticoids, like prednisone, hydrocortisone, or cyclosporine. 

How Zenrelia Works in Dogs

Ilunocitinib, the active ingredient in Zenrelia, is classified as a Janus kinase (JAK) inhibitor. 

Zenrelia works by blocking itch receptors under the skin, which prevents the itch signals from reaching your dog’s brain and reduces certain inflammatory processes triggered by allergies. Controlling your dog’s itch allows their red and inflamed skin to heal. 

Zenrelia is not a corticosteroid or an antihistamine. 

Zenrelia works by suppressing the immune system response, so sometimes it can be harder for a sick pet to fight infection when taking Zenrelia. 

How To Give Zenrelia to Dogs

Follow the directions on the drug label or as provided by your veterinarian. 

• Zenrelia is given once daily by mouth. 

• Zenrelia may be given with or without food. 

Missed a Dose? 

Speak with your veterinarian about what to do if you forget to give a dose of Zenrelia. 

Generally, your vet may instruct you to give it when you remember, or if it is almost time for your pet’s next dose, to skip the missed dose and resume your normal dosing schedule. 

Do not give extra or double doses. 

Possible Side Effects of Zenrelia for Dogs

The most common side effects include: 

• Digestive upset (nausea, vomiting, diarrhea, low appetite) 

• Low energy (tiredness) 

New growths, cancerous conditions (benign and malignant), and infections were observed during clinical studies. 

Less common side effects may include: 

• Eye discharge 

• Urinary tract infection 

• Low white blood cell count 

• Coughing, wheezing, upper respiratory infection, or difficulty breathing 

• Sneezing 

• Elevated liver level(s) 

• Bacterial skin infection 

• Ear infection (otitis externa) 

• Weight gain 

• Increased thirst 

Human Side Effects 

Zenrelia is a veterinary medication not intended for use in humans. 

Due to possible side effects, humans should never use medicine dispensed for their pets and pets should not be given any medicine dispensed for a human’s use. 

Wash your hands immediately after handling Zenrelia. 

If you accidentally ingest a pet medication, immediately seek medical attention in person. 

Monitoring Your Pet 

Dogs should be monitored for the development of infections because Zenrelia may increase the chances of developing an infection, including demodex skin mites, deep skin infections between the toes (interdigital dermatitis), coccidiosis, pneumonia, adenoviral hepatitis, and pancreatitis. 

Dogs should be monitored for the risk of decreased hematocrit, hemoglobin, and/or red blood cell count. 

Your veterinarian may recommend routine or additional testing depending on your dog’s individual needs, other medications they may be prescribed, and/or the issue that initially caused your dog to be placed on this medication. 

When To Call Your Vet 

Call your veterinarian if you see any of the following: 

• Severe side effects (above) 

• Your dog’s condition worsens or does not improve with treatment 

• You see or suspect an overdose 

• If you notice any signs of a possible new infection, like those mentioned in this article 

• If you have additional questions or concerns about the use of Zenrelia 

Your veterinarian may recommend routine or additional testing depending on your dog’s individual needs, other medications they may be prescribed, and/or the issue that initially caused your dog to be placed on this medication.

Zenrelia Overdose Concerns in Dogs

The severity of a Zenrelia overdose depends on the amount given by weight and for how long it was given. 

In safety studies, symptoms of an overdose over a period of weeks to months varied, including: 

• Swollen paws with deep infections between the toes (interdigital dermatitis) 

• Decreased red blood cell count, hematocrit (HCT), and hemoglobin (Hgb) 

• Enlarged lymph nodes 

• Papilloma growths between the toes 

• Depressed immune system 

• Pneumonia 

If you suspect an overdose, immediately seek emergency veterinary care or contact an animal poison control center. Consultation fees often apply. 

• Pet Poison Helpline 855-764-7661  

• ASPCA Animal Poison Control 888-426-4435  

How To Store Zenrelia for Dogs

Keep the following storage tips in mind for this medication: 

• Store at room temperature in between 59–77 F (15–25 C). Brief exposures of 41–104 F (5–40 C) are permitted. 

• Keep out of reach of children and pets.