Questions about Zenrelia™?
You may have questions about Zenrelia and how to use it on the itchy patients in your practice. Browse our general, administration, efficacy and safety frequently asked questions.
If your question is not answered or you want to discuss a specific case, please reach out to our ElancoVETS technical team via email or by telephone on +44(0)1256 353131, selecting option 1 for technical services.
General FAQs
Zenrelia is a newly licensed JAK inhibitor. It is approved for treatment of pruritus associated with allergic dermatitis in dogs, and for treatment of clinical manifestations of atopic dermatitis in dogs.
Zenrelia offers rapid and effective control of the most impactful symptoms of allergic and atopic dermatitis (pruritus and inflammation).1
Owners expect to see their dog get back to normal with treatment.4 Almost 4 out of 5 patients achieve such good control that they are no itchier than a healthy dog.1
Zenrelia has the added benefit of a simple once-daily treatment regime with or without food from the very start, and is priced so that more dogs can access the highly effective itch relief of JAK inhibitors for the long term.‡ Elanco offers a range of support tools for practices and pet owners who are ready to get started.
Administration FAQs
Zenrelia should be given once-daily (every 24 hours or as close as possible) from the start and for as long as needed.
There is no specific time of day that is best to administer Zenrelia. Zenrelia can be given with or without food. It is recommended to administer Zenrelia at approximately the same time each day, and in a consistent manner in relation to feeding.
Zenrelia can be used in dogs as small as 3kg. This is the minimum weight which can be accurately dosed with the tablet sizes available.
Zenrelia is indicated for dogs of 12 months and older. Use in dogs younger than 12 months is not recommended and should be based on a benefit/risk assessment by the responsible veterinary surgeon.
Zenrelia tablets come in the following sizes:
The tablet illustrations are for visual reference only and not actual size.There are 30 or 90 Zenrelia tablets in strips of 10.
Zenrelia is supplied in four different strengths, as scored tablets, allowing for accurate dosing of dogs as small as 3 kg. Dogs should be dosed according to the label dosing chart, once-daily. Zenrelia is available in 30 and 90 count boxes.
Yes, it can be used for short-term itch relief alongside a parasiticide to treat the dog for fleas.
Yes, Zenrelia can be effective for food allergies. Dogs with food allergies were included in the clinical trials for allergic dermatitis2, which covers various itchy skin conditions, including food allergies.
No. Zenrelia is a small, unflavoured, film-coated tablet.
Zenrelia is not flavoured to minimise the risk of exacerbating food allergy components of allergic dermatitis. Many flavouring agents can be potential allergens themselves, which could trigger a reaction in sensitive dogs. By keeping Zenrelia unflavoured, we aim to make it as tolerable as possible for a wider range of dogs, including those with food sensitivities.
Zenrelia is well accepted by dogs. In our extensive clinical field trials, involving more than 500 dogs treated by Zenrelia, none discontinued the study due to acceptance issues.1-3 It is a small tablet and can be given with or without food, and the film coating, whilst not flavoured, helps with acceptance.
Zenrelia can be dosed flexibly with or without food according to patient and owner preference and convenience.
Yes, the tablets are scored on both sides to facilitate accurate splitting. Any unused portion should be returned to the blister pack and used for the next dose, any remaining half tablets should be stored in the blister and discarded if not used within 20 days.
Store Zenrelia at room temperature (15-25°C). While brief exposure to temperatures between 5-40°C is acceptable, Elanco doesn't recommend using the product if stored outside these conditions long-term. The tablets remain stable for up to 6 months at 40°C and 24 months at 5°C, the safety and efficacy have not been evaluated under these conditions.
Two years from the time of manufacture.
No. Zenrelia is entirely free from pork, beef, soy, lactose and dairy.
Efficacy FAQs
Zenrelia is rapidly absorbed after oral administration and begins to work quickly, with visible improvements in pruritus within 24 hours after the first dose.1
Although many dogs experience very rapid itch relief with Zenrelia, it's generally advisable to wait at least a week before beginning to assess the response. The dog should start to be less itchy within the first few days, and you should see significant improvement by 2-4 weeks. If you have questions about a specific case, please contact our ElancoVETS technical team via email or by telephone on +44(0)1256 353131, selecting option 1 for technical services.
Yes, Zenrelia can be used during dietary food trials.
Key advantages include:
- The unflavoured tablet doesn't contain potential allergens like pork, beef, soy, lactose or dairy, which minimises the risk of affecting the trial.
- Once-daily dosing simplifies the regimen, which is particularly helpful when owners are already managing a strict elimination diet. This also makes it easier to restart Zenrelia if needed after reintroduction of a suspected allergen.
- Zenrelia has demonstrated excellent efficacy in controlling pruritus in dogs with various forms of allergic dermatitis, including atopic dermatitis, flea allergy dermatitis, food allergies and contact dermatitis.1-3
Yes, Zenrelia can be used intermittently during flare-ups, as it begins to work rapidly and has a convenient once-daily dosing schedule.
No, you would not expect to see a “rebound effect” in pruritus when treating dogs with Zenrelia.
In the European head-to-head clinical trial, efficacy measurements included: owner assessed level of itch using the Pruritus Visual Analog Scale (PVAS) and veterinarian-assessed lesion scoring using the 4-point Canine Atopic Dermatitis Extent and Severity Index (CADESI-4).1 Both of these measurement tools are validated outcome measures with established clinical relevance, with PVAS measuring improvement in itch and CADESI-4 measuring improvement in inflammation and skin lesions (which are also a reflection of itch level).4,5
To assess overall improvement, owners and veterinarians rated each dog's progress on a scale from 0 to 10, where 0 indicated no improvement and 10 represented excellent improvement.
Safety FAQs
Yes, Zenrelia is suitable for long-term use. The SPC doesn't specify any limitations on treatment duration. Because canine atopic and allergic dermatitis are chronic conditions often requiring ongoing management, Zenrelia's safety has been rigorously assessed in studies evaluating its long-term use.
No. There are no special precautions for the protection of the environment on the Zenrelia SPC. Our regulatory system ensures that all veterinary medicinal products undergo an independent scientific assessment for quality, efficacy and safety – this includes safety to the environment.
It is still important to ensure owners know how to use and dispose of products correctly, and are encouraged to return any unused or unwanted tablets for proper disposal. Owners should be advised to avoid flushing tablets down the toilet, for example.
The most common observations, as with many medications, were vomiting and diarrhoea, but for Zenrelia these occurred at very low rates over the 4-month study: 8.3% for vomiting, 4.1% for diarrhoea, and 2.4% for lethargy.1 Incidence of events does not necessarily imply causation. These low rates are reassuring and likely reflect what one might see in any dog population followed over 4 months. Papillomas & Interdigital cysts are also listed on the SPC as 'Uncommon'.
• Do not use in dogs with evidence of immune suppression.
• Do not use in cases of known hypersensitivity to the active substance or to any of the excipients.
There are no contraindications or special warnings for using Zenrelia with other medications. Zenrelia has been tested in real-world dogs who were receiving a wide variety of medications for other conditions. This included vaccines, antibiotics, parasiticides and NSAIDs1,3. See below for the full list of concomitant therapies administered during the EU clincal field trial.1 Use with other anti-pruritic medications such as glucocorticoids or cyclosporine has not been specifically evaluated. Zenrelia on its own has proven to be highly effective in the treatment of pruritus and clinical symptoms of atopic and allergic dermatitis. For further information, see Table S6 in the supporting information.
While there is no specific contraindication to using Zenrelia with any other product, we encourage you to perform a risk/benefit assessment and decide on a case-by-case basis. Particular considerations are listed on the SPC in section 3.8:
No drug interactions were observed in field studies where ilunocitinib was administered concomitantly with veterinary medicinal products such as endoand ectoparasiticides, antimicrobials, vaccines and non-steroidal antiinflammatory drugs.
The effect of ilunocitinib administration on vaccination with canine parvovirus (CPV), canine distemper virus (CDV), canine adenovirus-2 (CAV-2), canine parainfluenza (CPiV) and inactivated rabies vaccine (RV), has been studied in 10-month-old vaccine naïve dogs, receiving 2.4 mg/kg (3X the maximum recommended label dose) for 89 days. Based on assessment of serological antibody titres, an adequate immune response to canine core Modified Live Vaccines (CAV-2, CDV and CPV) was observed following primary vaccination on Day 28. Response to primary CPiV (non-core vaccine) vaccination in treated animals was 4 of 6 above threshold vs 6 of 8 controls above threshold following primary vaccination. A delayed or reduced response to RV was observed. The clinical relevance of these observed effects in animals vaccinated while being administered ilunocitinib in accordance with the recommended dosing regimen is unclear. The effect of ilunocitinib on response to booster vaccinations has been studied in 10-month-old previously vaccinated dogs receiving 1X or 3X the recommended label dose (0.6-0.8 or 1.8-2.4 mg/kg, respectively) for 56 days and showed no difference in booster vaccination response between control and 1X or 3X ilunocitinib treated groups.
It is appropriate to vaccinate dogs treated with Zenrelia. As with any other concomitant medication, a risk/benefit assessment should be performed by the responsible veterinary surgeon.
Zenrelia was used in conjunction with vaccinations during field trials with no interactions observed, and there is also a comprehensive study looking at its effect on booster vaccinations, which showed no difference in serological responses between control dogs and dogs being treated with Zenrelia, even at a 3x overdose.5
- Use in dogs younger than 12 months of age or weighing less than 3kg is not recommended and should be based on a benefit-risk assessment by the responsible veterinary surgeon.
- Ilunocitinib modulates the immune system and may increase susceptibility to opportunistic infection. Dogs receiving the veterinary medicinal product should be monitored for the development of infections and neoplasia.
- Do not use in dogs with evidence of malignant neoplasia, demodicosis or immune suppression such as hyperadrenocorticism, as the active substance has not been evaluated in these cases.
- When treating pruritus associated with allergic dermatitis, investigate and treat any underlying causes (e.g. flea allergic dermatitis, contact dermatitis, food hypersensitivity). Furthermore, in cases of allergic dermatitis and atopic dermatitis, it is recommended to investigate and treat complicating factors, such as bacterial, fungal or parasitic infections/infestations (e.g. flea and mange).
- Accidental ingestion may be harmful.
- In case of accidental ingestion, seek medical advice immediately and show the package leaflet or the SPC to the physician.
- Wash hands after administration.
- Keep tablets and unused half tablet in the original packaging until next administration, in order to prevent children from getting direct access to the veterinary medicinal product.
Use of Zenrelia has not been evaluated in dogs with hepatic or renal disease. Use of Zenrelia in these sub-populations should be according to a risk/benefit assessment by the responsible veterinary surgeon.
Use of Zenrelia in dogs with anaemia has not been evaluated and should be according to a risk/benefit assessment by the responsible veterinary surgeon.
The route of elimination of ilunocitinib is balanced between faecal and urinary route.
There is no specific requirement to do so, however establishing baseline bloodwork prior to starting a dog on any long-term medication and then conducting regular blood checks tailored to the individual case could be considered best practice and may be done at the discretion of the veterinary surgeon.
Any blood changes associated with Zenrelia are usually not clinically relevant. At the start of treatment, decreases in leukocyte (monocyte, eosinophil and neutrophil) counts and a reduction in red cell mass parameters (red blood cell count, haemoglobin and haematocrit) may be seen. These changes typically remain within the laboratory reference range and stabilise within the first month of treatment. However, periodic monitoring of complete blood counts and serum biochemistry may be advisable when dogs are on long-term treatment.
Zenrelia can be used in all dog breeds, as long as they meet the age and weight requirements (12 months or older and 3kg or heavier). There are no breed-specific contraindications for Zenrelia. However, as with any medication, individual responses can vary.
No. The safety of Zenrelia has not been established during pregnancy, lactation, or in breeding dogs. However, laboratory studies in rats have shown evidence of teratogenic & foetotoxic effects. Therefore, Zenrelia's use is not recommended during pregnancy, lactation or in dogs intended for breeding.
Zenrelia Resources
‡ Based on list price of Zenrelia as of 07/25 vs other licensed JAK inhibitors for dogs.
- Forster S, Boegel A, Despa S, et al. Comparative efficacy and safety of ilunocitinib and oclacitinib for the control of pruritus and associated skin lesions in dogs with atopic dermatitis. Veterinary Dermatology. 2025;36:165-176.
- Unpublished data (107): Field Study for Control of Pruritus Associated with Allergic Dermatitis.
- Forster S, Trout CM, Despa S, et al. Efficacy and field safety of ilunocitinib for the control atopic dermatitis in client- owned dogs: A multicentre, double- masked, randomised, placebo- controlled clinical trial. Veterinary Dermatology; 2025
- Rybníček J, Lau‐Gillard PJ, Harvey R, et al. Further validation of a pruritus severity scale for use in dogs. Veterinary Dermatology. 2009 Apr;20(2):115-22.
- Olivry T, Saridomichelakis M, Nuttall T, et al. International Committee on Allergic Diseases of Animals (ICADA). Validation of the Canine Atopic Dermatitis Extent and Severity Index (CADESI)‐4, a simplified severity scale for assessing skin lesions of atopic dermatitis in dogs. Veterinary Dermatology. 2014 Apr;25(2):77-e25.
- Kuntz EA, et al. Safety of ilunocitinib tablets (Zenrelia™) after once daily oral administration in dogs. BMC Veterinary Research. 2025;21:144.
- Fent, G.M., Jacela, J., Plazola-Ortiz, R. et al. BMC Vet Res 21, 481 (2025)
Zenrelia™ contains ilunocitinib. Legal category POM in IE, POM-V in UK (NI).
Information regarding the side effects, precautions, warnings and contra-indications can be found in product packaging and leaflets; further information can also be found in the Summary of Product Characteristics. Use medicines responsibly: APHA, NOAH . Advice should be sought from the prescriber prior to use. Prescription decisions are for the person issuing the prescription alone.
Zenrelia™, Elanco™ and the diagonal bar logo are trademarks of Elanco or its affiliates.
Apoquel® and Cytopoint® are trademarks of Zoetis UK Limited & Zoetis Belguim (IE).
For product related technical queries, contact the Elanco Vets team:
Telephone: +44(0)1256 353131, selecting option 1 for technical services
Email: ElancoVets@elanco.com*
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