Zenrelia is a prescription oral medication manufactured by Elanco for the control of pruritus (itching) associated with allergic dermatitis and the control of atopic dermatitis in dogs 12 months of age and older. FDA-approved in September 2024, Zenrelia represents a next-generation approach to the JAK inhibitor class, with selectivity for JAK1 over other JAK family members. In a head-to-head clinical trial against Apoquel (oclacitinib), Zenrelia demonstrated a statistically higher rate of itch remission (77% versus 53%), generating significant interest among veterinarians and pet owners seeking effective allergy management for dogs.
What Is Zenrelia Used For?
Zenrelia is prescribed for dogs with:
- Allergic dermatitis — itching and inflammation caused by environmental, food, or other allergen triggers
- Atopic dermatitis — a chronic skin condition involving immune-mediated inflammation and persistent itch
- Pruritus (itching) associated with allergic skin disease
Like other allergy medications, Zenrelia manages symptoms rather than curing the underlying allergy. Your veterinarian will develop a comprehensive plan that may also include identifying and avoiding allergens, dietary management, medicated shampoos, and other supportive treatments.
How Does Zenrelia Work?
Zenrelia works by selectively inhibiting Janus kinase 1 (JAK1), an enzyme involved in the signaling pathways that drive itch and inflammation in allergic skin disease. When allergens trigger an immune response, cytokines (signaling proteins) bind to cell receptors and activate JAK enzymes, which then relay signals that cause itching and inflammation. By blocking JAK1, Zenrelia interrupts this signaling cascade.
Zenrelia is described as JAK1-selective, meaning it preferentially inhibits JAK1 over other JAK family members (JAK2, JAK3, and TYK2). This selectivity is designed to target the most relevant itch and inflammation pathways while potentially reducing effects on pathways involved in immune defense and blood cell production. However, all JAK inhibitors have immunomodulatory effects, and veterinary monitoring is important.
Apoquel (oclacitinib) also inhibits JAK1 but has broader activity across JAK family members. The increased selectivity of Zenrelia may contribute to its clinical performance, though individual response to either medication varies.
Dosage
Zenrelia is dosed based on your dog’s body weight. Your veterinarian will determine the exact dose and treatment plan for your dog.
Zenrelia is given once daily. Unlike Apoquel, there is no loading phase with twice-daily dosing.
| Dog’s Weight | Recommended Dose |
|---|---|
| Weight-based | Your vet will prescribe the appropriate tablet strength |
Available tablet strengths and specific weight ranges are determined by your veterinarian based on the product labeling. The once-daily dosing is a practical advantage over Apoquel’s twice-daily loading phase.
How to Give Zenrelia to Your Dog
- Give Zenrelia once daily, at approximately the same time each day.
- Zenrelia can be given with or without food.
- Give the tablet whole. Do not break or crush unless directed by your veterinarian.
- If you miss a dose, give it as soon as you remember. If it is close to the next scheduled dose, skip the missed dose and continue the regular schedule. Do not double up.
- Keep all follow-up appointments with your veterinarian.
Important: Vaccination Washout Requirement
Zenrelia has a specific and important vaccination washout requirement that differs from other allergy medications. Because JAK inhibitors can affect immune function, Zenrelia may interfere with your dog’s ability to mount an adequate immune response to vaccines.
The FDA-approved label includes the following vaccination guidance:
- Before vaccination: Discontinue Zenrelia at least 28 days to 3 months before scheduled vaccinations (the specific interval depends on the vaccine type; your veterinarian will determine the appropriate washout period).
- After vaccination: Do not restart Zenrelia until at least 28 days after vaccination to allow the immune system to respond to the vaccine.
This means that if your dog needs annual vaccinations or booster shots, your veterinarian will need to plan a treatment break. During the washout period, your veterinarian may recommend alternative itch management strategies (such as Cytopoint injections, antihistamines, or short-term corticosteroids) to keep your dog comfortable.
Discuss your dog’s vaccination schedule with your veterinarian when starting Zenrelia so that treatment interruptions can be planned in advance.
Side Effects
Like all medications, Zenrelia can cause side effects. Most dogs tolerate it well, but monitoring is important, especially with long-term use.
| Common Side Effects | Serious Side Effects (Contact Your Vet) |
|---|---|
| Diarrhea | New or worsening infections (skin, ear, urinary) |
| Vomiting | Lumps or masses |
| Decreased appetite | Unusual lethargy or weakness |
| Mild lethargy | Bloody stool or vomiting |
| Signs of immune suppression |
Because all JAK inhibitors modulate the immune system, your veterinarian will recommend periodic blood work and monitoring during treatment, similar to the monitoring recommended for Apoquel.
Drug Interactions
Inform your veterinarian about all medications and supplements your dog is taking. Relevant considerations include:
- Corticosteroids (prednisone, dexamethasone): Concurrent use with JAK inhibitors may increase immunosuppression risk. Discuss with your veterinarian.
- Other immunosuppressive drugs (cyclosporine/Atopica, azathioprine): Combining immunomodulatory drugs may increase infection risk.
- Vaccines: See the vaccination washout section above. Zenrelia can interfere with vaccine response.
- NSAIDs: Consult your veterinarian regarding concurrent use.
Contraindications
Zenrelia should not be used in:
- Dogs under 12 months of age
- Dogs with serious, uncontrolled infections
- Dogs with a known hypersensitivity to the active ingredient
- Dogs used for breeding, or those that are pregnant or lactating (safety not established)
Storage
- Store at controlled room temperature.
- Keep in original packaging, protected from moisture.
- Keep out of reach of children and other pets.
Cost & Availability
Zenrelia is a prescription-only medication. There is no generic version available.
- Approximate monthly cost: Pricing is comparable to or slightly below Apoquel, though it varies by clinic and region
- Zenrelia is available through veterinary clinics and licensed pet pharmacies
Zenrelia vs. Apoquel: How Do They Compare?
| Feature | Zenrelia | Apoquel |
|---|---|---|
| Generic name | Lotilaner | Oclacitinib |
| Manufacturer | Elanco | Zoetis |
| Drug class | JAK1-selective inhibitor | JAK inhibitor (broader JAK1/JAK2) |
| FDA approved | September 2024 | 2013 |
| Dosing | Once daily (no loading phase) | Twice daily x14 days, then once daily |
| Itch remission rate (head-to-head trial) | 77% | 53% |
| Vaccination washout required | Yes (28 days-3 months before, 28 days after) | Not specifically labeled but immune effects acknowledged |
| Minimum age | 12 months | 12 months |
| Generic available | No | No |
The head-to-head clinical trial data showing 77% itch remission with Zenrelia versus 53% with Apoquel is based on published clinical trial results. However, individual dogs may respond differently to each medication, and some dogs that do not respond well to one may respond to the other. Your veterinarian will consider your dog’s complete health picture when recommending a treatment.
Frequently Asked Questions
Is Zenrelia better than Apoquel? In a head-to-head clinical trial, a higher percentage of dogs achieved itch remission with Zenrelia compared to Apoquel. However, “better” depends on the individual dog. Some dogs may respond to Apoquel but not Zenrelia, and vice versa. The vaccination washout requirement for Zenrelia is an important practical consideration. Your veterinarian can help determine which medication is most appropriate for your dog.
Why does Zenrelia require a vaccination washout? Because Zenrelia modulates the immune system through JAK1 inhibition, it may reduce your dog’s ability to develop a full immune response to vaccines. The washout period ensures your dog’s immune system can respond properly to vaccinations.
Can I switch from Apoquel to Zenrelia? Your veterinarian can guide you through a transition between medications. In many cases, a direct switch may be possible, but your vet will consider your dog’s vaccination schedule and any other factors.
How quickly does Zenrelia start working? Like Apoquel, Zenrelia is designed to provide relatively rapid itch relief. Many dogs show improvement within the first few days of treatment, though the full benefit may take longer. Response varies by individual.
Does Zenrelia require blood work monitoring? Your veterinarian will likely recommend periodic blood work, similar to monitoring protocols for Apoquel. This helps detect any changes in blood counts, liver values, or kidney function during treatment.
Sources & References
- FDA - Zenrelia (NADA) Approval Information
- FDA - Dear Veterinarian Letter: Zenrelia
- Elanco - Zenrelia Product Information
- Merck Veterinary Manual - Atopic Dermatitis in Dogs
- VCA Hospitals - Allergic Dermatitis in Dogs
This content is for informational purposes only and is not a substitute for professional veterinary advice. Always consult your veterinarian before starting, changing, or stopping any medication for your dog.