Oclacitinib for Controlling Pruritus and Associated Skin Lesions in 16 Horses With Allergic Dermatitis

BACKGROUND: Oclacitinib is a Janus kinase inhibitor approved for the treatment of pruritus associated with allergic dermatitis in dogs and may be effective in horses. OBJECTIVES: To evaluate the efficacy of oclacitinib in reducing pruritus and skin lesions in horses with allergic dermatitis. ANIMALS: Sixteen horses aged ≥ 18 months. MATERIALS AND METHODS: Horses received oclacitinib at 0.25 mg/kg orally once daily for 21 days. Changes in haematological and biochemical parameters were measured on Day (D)0 and D21. The owners were instructed to evaluate the horses using the pruritus Visual Analog Scale (PVAS) on D0, D4, D7, D10, D14, D17 and D21. A veterinary surgeon evaluated skin lesions using a veterinarian lesion score (VLS) and veterinarian alopecia score (VAS) on D0, D7, D14 and D21. RESULTS: From baseline to D21, the median (range) PVAS changed from 5 (4-8) to 2.5 (2-4.5), VLS from 19 (2-42) to 10 (1-38) and VAS from 2 (2, 3) to 2 (1, 2). Of all 16 horses, improvements in PVAS, VLS and VAS were observed in 15, 12 and 8 horses, respectively. Blood profiles revealed significantly increased aspartate aminotransferase, gamma-glutamyl transferase and creatinine levels. White blood cell count, lymphocyte count and blood urea nitrogen significantly decreased. Creatine kinase levels showed individual variability. CONCLUSIONS AND CLINICAL RELEVANCE: Oclacitinib effectively reduced pruritus and improved skin lesions in horses with allergic dermatitis. However, caution is advised when administering the drug to horses with renal, hepatic or muscular disorders.