Apoquel (Oclacitinib)

Janus kinase (JAK) inhibitor Immunomodulatory agent

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog PO 0.4-0.6 mg/kg q12h for up to 14 days, then q24h for maintenance Duration: For allergic dermatitis: initial 14 days twice daily, then once daily for maintenance; for atopic dermatitis: can be used long-term as needed
Notes: Administer with or without food. For dogs weighing less than 3 kg, use appropriate formulation. Doses should be based on body weight and adjusted for response.

Clinical Indications & Species Uses

General Indications
  • Pruritus associated with allergic dermatitis in dogs
Dog (Canine)
  • Control of pruritus associated with allergic dermatitis
  • Control of atopic dermatitis
Cat (Feline)
  • Not approved for use in cats; safety and efficacy not established

Pharmacology & Mechanism of Action

Drug Class: Janus kinase (JAK) inhibitor | Pharmacological Group: Immunomodulatory agent

Mechanism of Action: Oclacitinib is a selective inhibitor of Janus kinase 1 (JAK1), which is involved in the signaling of multiple pro-inflammatory and pruritogenic cytokines, including IL-2, IL-4, IL-6, IL-13, and IL-31. By inhibiting JAK1, oclacitinib reduces the phosphorylation and activation of signal transducers and activators of transcription (STAT) proteins, thereby decreasing the production of inflammatory mediators and cytokines that drive pruritus and allergic inflammation. It has selectivity for JAK1 over JAK2 and JAK3, which helps minimize effects on hematopoiesis and immune function.

Pharmacodynamics: Oclacitinib rapidly reduces pruritus in dogs with allergic dermatitis, with significant improvement often seen within 24 hours. It suppresses the inflammatory response by inhibiting cytokine signaling, leading to decreased erythema, self-trauma, and skin lesions. It does not have direct antihistamine or corticosteroid-like effects. Its effects on cytokine signaling are reversible upon discontinuation.

⚡ Pharmacokinetics Summary

Absorption: Oclacitinib is well absorbed after oral administration in dogs, with peak plasma concentrations occurring approximately 1-2 hours post-dose. Food does not significantly affect absorption.
Distribution: Oclacitinib has a moderate volume of distribution, indicating distribution into tissues. It is approximately 66-77% bound to plasma proteins in dogs.
Metabolism: Oclacitinib is extensively metabolized in the liver, primarily by cytochrome P450 enzymes (CYP3A4 and CYP2C9) and other pathways. Multiple metabolites are formed, but the parent drug is the primary active moiety.
Excretion: Oclacitinib is eliminated primarily via metabolism, with metabolites excreted in urine and feces. In dogs, the terminal half-life is approximately 4-5 hours after oral administration.
Half-Life: Dogs: ~4-5 hours
Bioavailability: Approximately 80-90% in dogs after oral administration
Protein Binding: 66-77% in dogs

Available Formulations & Strengths

Oral Tablet 3.6 mg, 5.4 mg, 7.2 mg, 10.8 mg, 16 mg, 21.6 mg, 25 mg (PO)

Contraindications & Clinical Warnings

Contraindications:
  • Hypersensitivity to oclacitinib or any component of the formulation
  • Dogs with serious infections (should not be used in dogs with active severe infections)
  • Dogs with demodicosis (mange) should be treated for the underlying condition before starting oclacitinib
  • Use in breeding, pregnant, or lactating dogs is not recommended (safety not established)
Warnings & Clinical Precautions:
  • Use with caution in dogs with a history of seizures or neurologic disorders
  • May increase susceptibility to infections (e.g., demodectic mange, pyoderma) due to immunomodulation
  • Monitor for new or worsening neoplasia (lymphoma has been reported in some dogs)
  • Not for use in dogs less than 12 months of age or weighing less than 3 kg
  • Use with caution in dogs with hepatic or renal impairment
  • Do not use concurrently with other immunosuppressive drugs (e.g., corticosteroids, cyclosporine) unless directed by a veterinarian
  • Vaccination: Safety of concurrent vaccination has not been fully evaluated; consider timing of vaccinations

Adverse Effects & Reactions

Common:

  • Vomiting
  • Diarrhea
  • Decreased appetite
  • Lethargy
  • Otitis externa

Serious / Severe:

  • New or worsening infections (e.g., pyoderma, demodicosis)
  • Lymphoma (rare but reported)
  • Seizures (rare)
  • Hepatopathy (rare)

Rare:

  • Anemia
  • Thrombocytopenia
  • Pancreatitis
  • Interstitial nephritis

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Corticosteroids (e.g., prednisone) Concurrent use may increase risk of immunosuppression and gastrointestinal ulceration; avoid unless specifically indicated High
Cyclosporine Additive immunosuppressive effects; may increase risk of infections Moderate
Fluconazole or other CYP3A4 inhibitors May increase oclacitinib plasma concentrations; monitor for adverse effects Moderate
Ketoconazole May increase oclacitinib exposure; use with caution Moderate

Overdose & Toxicity Management

Signs of Toxicity:

  • Vomiting
  • Diarrhea
  • Lethargy
  • Anorexia
  • Depression

Emergency Treatment Protocol: There is no specific antidote. Treatment is symptomatic and supportive. Induce vomiting if recent ingestion and the animal is conscious. Administer activated charcoal to reduce absorption. Monitor for clinical signs and provide supportive care (fluids, antiemetics, etc.). In severe cases, consider hospitalization.

Food Animal Withdrawal Times

Not approved for use in food animals; no withdrawal times established. Use in food animals is prohibited.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature 20°C to 25°C (68°F to 77°F); excursions permitted between 15°C and 30°C (59°F and 86°F)

Handling & Special Conditions: Keep in a dry place, protect from moisture. Keep out of reach of children and pets.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved by FDA for use in dogs for control of pruritus associated with allergic dermatitis and control of atopic dermatitis.

Extra-Label (Off-Label) Use: In the US, extra-label use in dogs is permitted under AMDUCA if a valid veterinarian-client-patient relationship exists, but use in food animals is prohibited. In other countries, follow local regulations.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Apoquel (oclacitinib) is a first-line treatment for allergic dermatitis and atopic dermatitis in dogs. It provides rapid relief from pruritus, often within 24 hours, and is generally well-tolerated. It is important to rule out other causes of pruritus (e.g., flea allergy, food allergy, infections) before starting therapy. Long-term use may require periodic monitoring of complete blood count, serum biochemistry, and urinalysis, especially in older dogs. Avoid concurrent use with other immunosuppressive agents. If clinical signs do not improve within 2 weeks, reassess the diagnosis. For refractory cases, consider alternative or adjunctive therapies. Always use the lowest effective dose for maintenance.

References & Literature

  • 📚 Plumb's Veterinary Drug Handbook
  • 📚 Papich Veterinary Pharmacology and Therapeutics
  • 📚 Compendium of Veterinary Products (CVP)