The most commonly used analgesic medications (nonsteroidal anti-inflammatory drugs) in equine medicine, though efficacious, may be limited for long term use due to accompanying side effects, particularly those affecting the gastrointestinal and urinary tracts. The use of cannabinoid products may represent a valuable alternative by offering an analgesic effect through nociceptive modulation in equine patients with chronic osteoarthritis. However, there is minimal pharmacokinetic, or safety data published regarding administration of cannabidiol (CBD)-based products in veterinary patients. Recently, safety and pharmacokinetics of a commercial product by Ellevet Sciences LLC was evaluated in dogs. The information obtained validated the canine dose of that particular CBD product, and its efficacy in reducing pain with negligible short-term side effects. With growing interest in the use of hemp derived products in veterinary medicine, it is important to have data confirming the species-specific safety and efficacy of these products. Moreover, different products contain variable proportion of CBD and its precursor cannabidiolic acid (CBDA). Only recently, it has been shown in dogs that CBDA absorption is twice that of CBD, but the specific pharmacokinetics of CBD and CBDA has not being elucidated in other species.

The goals of this study are to provide (1) basic oral pharmacokinetic data for CBD and CBDA, and a 12- week (2) safety and (3) analgesic efficacy assessment regarding administration of CBD and CBDA oil to horses with varying degrees of chronic lameness.