IRAP, which stands for Interleukin-1 Receptor Antagonist Protein, is an anti-inflammatory treatment for joint disease in horses that works by counteracting the pro-inflammatory cascade triggered by the protein interleukin-1. Interleukin-1 (IL-1) is a pro-inflammatory protein that is found in increased quantities in unhealthy joints, such as those suffering from osteoarthritis. IL-1 is a potent chemical signal that activates many other harmful cytokines along the pathway of inflammation within the joint. Release of IL-1 and other pro-inflammatory cytokines leads to a downward spiral of inflammation and joint disease, resulting in cartilage damage and osteoarthritis. As tissue damage increases within the joint, additional IL-1 is produced, perpetuating the vicious cycle of inflammation and osteoarthritis.

IRAP works in the horse by blocking IL-1 from binding to its receptor inside the joint, thus stopping the cascade of inflammation triggered by IL-1, and slowing the progression of osteoarthritis.


A typical treatment with IRAP begins by harvesting approximately 50 mL of blood from your horse’s jugular vein. The blood is then incubated overnight in a syringe that contains pretreated glass beads designed to isolate and amplify the horse’s naturally occurring IRAP. The IRAP is then concentrated by spinning in a centrifuge, and is sterilely prepared into individual dose syringes for injection back into your horse. These syringes are stored in a freezer until they are ready to be used. IRAP is typically injected into a joint once every 7-10 days for 3-5 treatments total.

Cases with lameness isolated to specific joints that demonstrate mild to moderate radiographic changes associated with degenerative joint disease tend to respond the best to treatment with IRAP. Additionally, horses with joint disease who have failed to respond to other more traditional joint therapies like corticosteroid injections, are good candidates for IRAP treatment. IRAP is also frequently used as a post-surgical joint therapy for cases with focal cartilage damage or other associated soft-tissue injuries found at surgery.