Side Effects of Apoquel in Dogs: What Every Owner Should Know
Learn about the side effects of Apoquel in dogs, including common reactions, serious risks, dosage guidelines, and what to discuss with your veterinarian.
What Is Apoquel and What Is It Used For in Dogs?
Apoquel is the brand name for oclacitinib maleate, a prescription medication manufactured by Zoetis specifically for veterinary use. It is FDA-approved for two primary indications in dogs:
- Control of pruritus (itching) associated with allergic dermatitis in dogs 12 months of age or older
- Control of atopic dermatitis (environmental allergies) in dogs 12 months of age or older
Since its FDA approval in 2013, Apoquel has become one of the most widely prescribed dermatological medications in veterinary medicine. According to Zoetis, it has been prescribed for over 30 million dogs worldwide. Its popularity stems from its rapid onset — most dogs experience significant itch relief within 4 hours of the first dose, with full control typically achieved within 24 hours.
While allergic dermatitis and atopic dermatitis are the approved uses, veterinarians sometimes prescribe Apoquel off-label for other pruritic conditions, including:
- Food allergy-related itching (as a bridge while conducting elimination diet trials)
- Contact dermatitis
- Pruritus secondary to flea allergy dermatitis (alongside flea control)
- Idiopathic pruritus where the underlying cause cannot be identified
How Does Apoquel Work? The Mechanism of Action Explained
Drug Class: Janus kinase (JAK) inhibitor — specifically a selective JAK1 inhibitor
How It Works: Apoquel blocks specific enzymes called Janus kinases (primarily JAK1) that are involved in the signaling pathways of several cytokines responsible for itching and inflammation. By inhibiting JAK1, Apoquel interrupts the itch signal before it reaches the brain, effectively stopping the scratch-itch cycle at the cellular level.
Unlike corticosteroids (such as prednisone), which broadly suppress the immune system, Apoquel targets the specific pathways involved in itch sensation. This more selective mechanism is why many veterinarians prefer it for long-term allergy management — it avoids many of the systemic side effects associated with chronic steroid use, such as increased thirst, urination, appetite, and potential liver or adrenal effects.
However, this selectivity does not mean Apoquel is without immune effects. JAK1 is involved in signaling for several cytokines, including some related to immune surveillance. This is why understanding the side effects of Apoquel in dogs is essential for any owner whose pet is on this medication.
Typical Dosage of Apoquel: What Your Veterinarian Will Prescribe
Apoquel is available in three tablet strengths: 3.6 mg, 5.4 mg, and 16 mg. Your veterinarian will determine the correct dose based on your dog's weight, and the dose is calculated at approximately 0.4 to 0.6 mg per kilogram of body weight (0.18 to 0.27 mg per pound), administered orally twice daily for up to 14 days, then reduced to once daily for maintenance.
| Dog Weight | Initial Phase (Days 1–14) | Maintenance Phase (Day 15+) | Tablet Strength Used |
|---|---|---|---|
| 6.6–9.9 lb (3–4.5 kg) | 3.6 mg twice daily | 3.6 mg once daily | 3.6 mg tablet |
| 10–14.9 lb (4.5–6.8 kg) | 5.4 mg twice daily | 5.4 mg once daily | 5.4 mg tablet |
| 15–19.9 lb (6.8–9 kg) | 5.4 mg twice daily | 5.4 mg once daily | 5.4 mg tablet |
| 20–29.9 lb (9–13.6 kg) | 5.4 mg twice daily | 5.4 mg once daily | 5.4 mg tablet |
| 30–39.9 lb (13.6–18.1 kg) | 5.4 mg twice daily | 5.4 mg once daily | 5.4 mg tablet |
| 40–59.9 lb (18.1–27.2 kg) | 16 mg twice daily | 16 mg once daily | 16 mg tablet |
| 60–89.9 lb (27.2–40.8 kg) | 16 mg twice daily | 16 mg once daily | 16 mg tablet |
| 90–129.9 lb (40.8–59 kg) | Two 16 mg tablets twice daily | Two 16 mg tablets once daily | 16 mg tablets |
Administration instructions:
- Apoquel can be given with or without food — absorption is not significantly affected by meals
- Tablets are not flavored, so you may need to hide them in a small treat or pill pocket
- The twice-daily initial phase should not exceed 14 days without veterinary direction
- Do not split tablets unless directed by your veterinarian — the 3.6 mg and 5.4 mg strengths are designed for smaller dogs
Common Side Effects of Apoquel in Dogs
In pre-approval clinical trials and post-market surveillance, the most frequently reported side effects of Apoquel in dogs have been relatively mild and gastrointestinal in nature. According to Merck Veterinary Manual and the FDA-approved label, the following side effects were observed:
| Side Effect | Reported Frequency | Severity | What to Watch For |
|---|---|---|---|
| Diarrhea | ~2.9% | Mild | Loose stools, usually resolves within a few days |
| Vomiting | ~2.5% | Mild | May improve when given with food |
| Decreased appetite | ~1.4% | Mild | Reduced food intake, monitor weight |
| Lethargy | ~1.2% | Mild | Increased sleepiness, reduced activity |
| Skin infections (pyoderma) | ~2.0% | Moderate | Red, hot, or oozing skin lesions |
| Ear infections (otitis) | ~1.5% | Moderate | Head shaking, ear odor, scratching at ears |
| Increased thirst (polydipsia) | <1% | Mild | Drinking more water than usual |
| Demodicosis (demodex mite flare) | <1% | Moderate | Hair loss, scaly patches, skin thickening |
The overall rate of adverse events in clinical trials was low — most dogs (over 95%) tolerated Apoquel without noticeable side effects. The gastrointestinal effects (vomiting and diarrhea) were the most common but typically transient, resolving within the first week of treatment. Administering the tablet with a small meal can reduce the likelihood of stomach upset.
Serious Side Effects and Warning Signs That Require Immediate Veterinary Attention
While rare, some dogs experience more serious reactions to Apoquel. Because oclacitinib modulates the JAK pathway involved in immune function, there are specific concerns with long-term use that every dog owner should monitor:
🚨 Call Your Veterinarian Immediately If Your Dog Develops:
- New or worsening skin infections — recurrent pyoderma, hot spots, or yeast infections that don't respond to standard treatment
- Unexplained lumps, bumps, or masses — Apoquel is not approved for use in dogs with a history of cancer, and immune modulation may theoretically affect tumor surveillance
- Significant lethargy or behavioral changes — unusual depression, disorientation, or weakness
- Persistent vomiting or diarrhea — lasting more than 48 hours or accompanied by blood
- Signs of pneumonia or respiratory infection — coughing, labored breathing, nasal discharge
- Unexplained weight loss — especially if appetite remains normal
- Increased susceptibility to infections — urinary tract infections, recurrent ear infections, or infections that take longer to resolve than expected
The relationship between Apoquel and neoplasia (cancer) has been carefully studied. In long-term safety studies, there was no statistically significant increase in cancer rates in dogs receiving Apoquel compared to placebo. However, the FDA label notes that Apoquel has not been evaluated in dogs with pre-existing cancer, and veterinarians generally exercise caution when prescribing it to dogs with a history of neoplasia.
Similarly, because JAK inhibition can affect immune cell function, dogs on long-term Apoquel may have a slightly elevated risk of opportunistic infections. This is why regular veterinary monitoring is essential — not optional.
Who Should NOT Take Apoquel: Contraindications and Drug Interactions
Apoquel is not appropriate for every dog. The following contraindications are established based on the FDA label and clinical data:
Contraindications — Dogs Who Should Not Receive Apoquel
- Dogs under 12 months of age — safety has not been established in puppies, and immune system development could be affected
- Dogs with serious infections — active bacterial, viral, fungal, or parasitic infections should be resolved before starting Apoquel
- Dogs with a history of cancer (neoplasia) — Apoquel has not been evaluated in dogs with cancer, and immune modulation is a theoretical concern
- Dogs used for breeding, pregnant dogs, or lactating dogs — safety has not been established in these populations
- Dogs with known hypersensitivity to oclacitinib — though extremely rare, allergic reactions to the drug itself are possible
Drug Interactions
| Concurrent Medication | Interaction Risk | Veterinary Guidance |
|---|---|---|
| Corticosteroids (prednisone, dexamethasone) | Additive immunosuppression — increased infection risk | Generally avoided together; if combined, requires close monitoring |
| Cyclosporine (Atopica) | Dual immune modulation — compounded immunosuppressive effects | Not recommended concurrently; your vet will choose one or the other |
| NSAIDs (carprofen, meloxicam) | Low direct interaction risk, but combined GI effects possible | Generally safe to combine; monitor for vomiting or GI bleeding |
| Antibiotics and antifungals | No significant direct interactions documented | Safe to use concurrently for secondary infections |
| Flea/tick preventives (isoxazolines) | No documented interactions | Safe to use concurrently; flea control is essential for allergic dogs |
| Heartworm preventives | No documented interactions | Safe and recommended to continue heartworm prevention |
Always provide your veterinarian with a complete list of every medication, supplement, and over-the-counter product your dog is currently receiving before starting Apoquel. This includes topical products, joint supplements, and any herbal remedies.
Monitoring Requirements: Blood Work and Follow-Up Visits
One of the most important aspects of responsible Apoquel use is ongoing veterinary monitoring. While the drug does not require the intensive blood work monitoring that cyclosporine demands, regular check-ups are still essential — especially for dogs on long-term therapy.
Recommended Monitoring Schedule for Dogs on Apoquel
| Timeframe | What to Monitor | Typical Cost Range |
|---|---|---|
| Baseline (before starting) | Complete physical exam, CBC (complete blood count), chemistry panel; rule out infections and pre-existing conditions | $150–$300 |
| 2–4 weeks after starting | Assess efficacy (itch reduction), check for GI side effects, evaluate for any emerging infections | $60–$120 (exam fee) |
| Every 6 months (long-term use) | CBC, chemistry panel, physical exam, skin/ear evaluation, body condition assessment | $150–$300 per visit |
| Annual comprehensive check | Full blood work, urinalysis, thorough physical exam including lymph node palpation and skin mass check | $200–$400 |
Your veterinarian may recommend more frequent monitoring if your dog is senior (over 7–8 years old), has concurrent health conditions, or is taking other medications alongside Apoquel. Some veterinary dermatologists recommend a CBC every 3 months for the first year, then every 6 months thereafter — though this varies by practice and individual patient.
How Long Does My Dog Need to Be on Apoquel?
The duration of Apoquel therapy depends entirely on the underlying condition and your dog's individual response:
- Seasonal allergies: Some dogs only need Apoquel during peak allergy seasons (spring/fall) — typically 2 to 4 months per year. Your vet may start and stop the medication as needed.
- Year-round environmental allergies: Dogs with perennial atopic dermatitis (dust mites, mold, dander) may need Apoquel continuously. Long-term safety studies have followed dogs on Apoquel for over 2 years without significant adverse trends, but lifelong therapy should always be a shared decision with your veterinarian.
- Short-term flare management: Some veterinarians use Apoquel to quickly control acute itch flares while implementing longer-term strategies like allergen-specific immunotherapy (allergy shots or sublingual drops).
A common misconception is that Apoquel is a "cure" for allergies. It is not — it is a symptom management tool. The underlying allergic sensitization remains, and if Apoquel is discontinued, itching will typically return within 24 to 72 hours if the allergen exposure continues. This is why many veterinary dermatologists recommend using Apoquel alongside other strategies:
- Allergen-specific immunotherapy (ASIT) to retrain the immune system
- Regular bathing with medicated shampoos to reduce allergen load on the skin
- Environmental control measures (HEPA filters, frequent bedding washing)
- Strict flea control to prevent flea allergy dermatitis from compounding the problem
- Omega-3 fatty acid supplementation to support skin barrier function
Cost of Apoquel and Generic Availability
Apoquel is a brand-name medication manufactured by Zoetis, and as of 2026, there is no FDA-approved generic equivalent (oclacitinib) available in the United States. This means costs remain relatively high compared to older allergy medications like antihistamines or prednisone.
Typical cost ranges (2026 estimates):
| Tablet Strength | Cost Per Tablet (Approximate) | Monthly Cost (Once Daily) |
|---|---|---|
| 3.6 mg | $2.50–$3.50 | $75–$105 |
| 5.4 mg | $3.00–$4.25 | $90–$128 |
| 16 mg | $4.50–$6.50 | $135–$195 |
For large-breed dogs requiring the 16 mg strength (or two tablets per dose), annual Apoquel costs can reach $1,600–$2,400+ per year. This is a significant financial commitment, and pet owners should factor this into their annual veterinary budget. Pet insurance plans that cover prescription medications may offset some of this cost, but pre-existing condition exclusions typically apply — so enrolling before allergies develop is important.
You can purchase Apoquel through your veterinarian's office, through veterinary online pharmacies (such as Chewy's vet-authorized pharmacy or 1-800-PetMeds with a valid prescription), or through some veterinary chains that carry in-house pharmacies. Always verify that any online pharmacy is VIPPS-accredited (Verified Internet Pharmacy Practice Sites) or Vet-VIPPS certified to avoid counterfeit medications.
What to Do If You Miss a Dose or Suspect an Overdose
Missed Dose
If you miss a scheduled dose of Apoquel:
- Give the missed dose as soon as you remember, unless it is close to the time of the next scheduled dose
- If it is within a few hours of the next dose, skip the missed dose and resume the regular schedule
- Never double the dose to make up for a missed one
- A single missed dose will not cause a severe flare — but your dog's itching may begin to return within 24 hours
Suspected Overdose
In safety studies, dogs were administered oclacitinib at doses up to 10 times the recommended dose for 6 months. While no life-threatening effects were observed at these elevated doses, the incidence of gastrointestinal side effects (vomiting, diarrhea, decreased appetite) and skin infections increased significantly.
If you suspect your dog has ingested more Apoquel than prescribed:
- Contact your veterinarian or an emergency veterinary clinic immediately
- Call the ASPCA Animal Poison Control Center at (888) 426-4435 (24/7, consultation fee applies) for guidance
- Have the medication packaging available to provide the exact strength and estimated quantity consumed
- Monitor for vomiting, diarrhea, lethargy, or loss of appetite
Are There Alternatives to Apoquel for Managing Allergies in Dogs?
Apoquel is not the only option for canine allergy management, and depending on your dog's specific situation, your veterinarian may recommend or combine other therapies. Here is a comparison of the main alternatives:
| Alternative | How It Works | Onset of Action | Typical Monthly Cost | Best For |
|---|---|---|---|---|
| Cytopoint (lokivetmab) | Monoclonal antibody injection targeting IL-31 (itch cytokine) | 24–48 hours | $65–$150 per injection (every 4–8 weeks) | Dogs who can't take oral meds; dogs with liver concerns |
| Cyclosporine (Atopica) | Broad immunosuppressant targeting T-cell activation | 4–6 weeks | $80–$200+ | Dogs who don't respond to Apoquel; long-term management |
| Allergen-specific immunotherapy (ASIT) | Gradually desensitizes immune system to specific allergens | 3–12 months | $50–$150 (after initial $300–$600 testing) | Young dogs with identified allergens; long-term cure potential |
| Corticosteroids (prednisone) | Broad anti-inflammatory and immunosuppressive | Hours | $10–$30 | Short-term flare control; budget-conscious owners |
| Antihistamines (cetirizine, diphenhydramine) | Histamine receptor blockade | 1–2 hours | $5–$15 | Mild cases; adjunctive therapy; only effective in ~20–30% of dogs |
Many veterinary dermatologists use a multimodal approach — for example, starting with Apoquel for rapid itch relief while simultaneously beginning allergen-specific immunotherapy, which takes months to show results. Once ASIT becomes effective, Apoquel can often be tapered or discontinued entirely.
The American Kennel Club's veterinary resources note that the choice between Apoquel and alternatives like Cytopoint often comes down to the individual dog's health profile, owner preference (daily pill vs. periodic injection), and cost considerations.
Frequently Asked Questions About Apoquel Side Effects
Can Apoquel cause behavioral changes in dogs?
Behavioral changes are not among the commonly reported side effects of Apoquel. However, any dog experiencing discomfort from a side effect (such as GI upset) or from an undetected infection may exhibit behavioral changes like irritability, restlessness, or withdrawal. If you notice significant behavioral changes after starting Apoquel, consult your veterinarian to determine whether the medication or another underlying issue is responsible.
Does Apoquel cause weight gain in dogs?
Unlike corticosteroids, Apoquel does not typically cause weight gain or increased appetite. Weight gain is not listed as a reported side effect in clinical trials. If your dog gains weight while on Apoquel, it is more likely related to reduced activity (if the dog was previously too uncomfortable to exercise) or dietary factors unrelated to the medication.
Is it safe to stop Apoquel suddenly?
Yes — unlike corticosteroids, Apoquel does not require a tapering schedule. You can stop it abruptly if directed by your veterinarian. However, be aware that your dog's itching will likely return within 1 to 3 days if the underlying allergen exposure has not been addressed. Never stop or change your dog's medication schedule without discussing it with your veterinarian first.
Can Apoquel be used alongside allergy shots (immunotherapy)?
Yes, Apoquel is frequently used alongside allergen-specific immunotherapy. In fact, this is considered best practice by many veterinary dermatologists. Apoquel provides immediate itch relief while the immunotherapy (which can take 3–12 months to become effective) builds long-term tolerance. Once immunotherapy is working, your veterinarian may taper the Apoquel dose or discontinue it entirely.
My dog has been on Apoquel for years — should I be concerned?
Long-term safety data from Zoetis and independent studies have not identified a significant increase in serious adverse events in dogs on Apoquel for extended periods. However, the key is consistent veterinary monitoring. Dogs on long-term Apoquel should have blood work checked at least every 6 months, with a thorough physical exam including lymph node palpation and full-body skin checks to screen for any masses. If your dog has been on Apoquel for years without regular blood work, schedule a comprehensive check-up with your veterinarian.
Can I give my dog Apoquel that was prescribed for another dog?
No. Apoquel dosing is weight-specific, and the medication may not be appropriate for a dog with different health conditions, age, or concurrent medications. Sharing prescription medications between dogs is unsafe and potentially illegal. Always obtain a separate prescription from your veterinarian for each individual dog.
Disclaimer: This article is for informational purposes only and does not replace professional veterinary advice. Always consult your veterinarian before starting, stopping, or adjusting any medication for your dog. If you suspect an adverse drug reaction, contact your veterinarian or the ASPCA Animal Poison Control Center at (888) 426-4435.
Beth Carrasco
All our authors care for dogs every day — read more of their work on the authors page.
