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Imagine finally quelling your horse’s insatiable urge to rub, scratch, roll, and bite at himself in an attempt to relieve his allergic itch. Because antihistamines are sometimes ineffective and corticosteroids have unwanted side effects, some researchers are eyeing an itch-relieving alternative, a drug called oclacitinib maleate.

Common allergens for horses include insect bites, certain vegetation (grasses, weeds, trees), bedding, and some grooming products.

Medical treatment options for itchy horses, as mentioned above, are fairly limited and often yield underwhelming results. As an alternative to medications, itchy horses sometimes find reprieve through supplementation of omega-3 fatty acids.

“The omega-3s DHA and EPA are incorporated into cell membranes throughout the body, including skin cells. They have been shown to counter inflammation in several ways, such as inhibiting the production of inflammatory proteins responsible for allergic reactions,” explained Kathleen Crandell, Ph.D., a nutritionist for Kentucky Equine Research.

Oclacitinib also has anti-inflammatory effects as it targets various pro-inflammatory mediators. This includes interleukin-31, also known as the “pruritus cytokine.” Pruritus is synonymous with itchy.

Preliminary studies and anecdotal evidence support using oclacitinib in horses. Most recently, researchers from Texas A&M University conducted a pharmacokinetic study to measure blood levels of oclacitinib in horses after oral administration.

Six healthy horses were given oclacitinib at a dose of 0.5 mg/kg, the FDA-approved recommended dose of this medication in dogs, which was top-dressed on feed. Blood samples were collected immediately prior to dosing and intermittently between 15 minutes and 72 hours afterward.

“The data showed that oclacitinib was rapidly absorbed after oral administration, with peak blood levels occurring two hours after administration,” relayed Crandell.

While these results are promising, this research simply scratches the surface of the pharmacokinetics and pharmacodynamics associated with oclacitinib. Additional studies on the drug’s absorption, metabolism, and elimination are needed, and clinical efficacy and safety must also be evaluated.

“Treating itchy horses can be very frustrating. Even if omega-3 fatty acids cannot fully relieve your horse’s itch, they certainly play a valuable role in a multimodal treatment approach in addition to allergen avoidance whenever possible,” recommended Crandell.

*Hunyadi, L., P. Datta, K. Rewers-Felkins, E. Sundman, T. Hale, V. Fajt, and S. Wagner. 2022. Pharmacokinetics of a single dose of oclacitinib maleate as a top dress in adult horses. Journal of Veterinary Pharmacology and Therapeutics 13043.

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