IRAP (interleukin Receptor Antagonist Protein)


Lameness caused by osteoarthritis (degenerative joint disease) is a major concern in the competitive horse world. Time and money is lost while the horse is laid up and recovering, and treatments have been limited to systemic anti-inflammatories (Bute, Banamine, Equioxx, etc), topical anti-inflammatories (Surpass, DMSO), and intra-articular injections of hyaluronic acid and steroids. Injectable products like Adequan IM and Legend IV, and oral joint supplements (glucosamine, chondroitin sulfate, and HA) may also be of benefit.

Injected directly into the affected joint, IRAP (Interleukin Receptor Antagonist y

Protein) is different in several ways. First of all, it is an autologous product. Like PRP (Platelet Rich Plasma, which is typically injected into damaged tendons and ligaments), IRAP is created from the horse’s own blood. After a sterile prep, blood is drawn into a syringe that contains special beads. While the blood is incubated for about 24 hours, these beads stimulate production of a specific protein-- IRAP. 1

The serum containing the IRAP is separated from the rest of the blood, and frozen in 2-8cc volumes for later use (amount depends on specific joint to be treated). Most often, four to six treatments can be produced from one blood draw. The joint is then injected with the thawed IRAP several times, typically seven to fourteen days apart, and the horse is in minimal exercise during treatment. The most dramatic visual change is the dramatic increase in the quality of joint fluid. As therapy continues the viscosity of the synovial fluid gets thicker and thicker as the inflammation that breaks down the consistency is blocked.


How does this happen?

Trauma to the joint from work, injury, genetic predisposition, developmental abnormalities, and age causes inflammation that shows up as lameness, joint swelling, and pain on flexion or extension. This trauma causes release of inflammatory proteins, known as cytokines: one of which is Interleukin-1  (IL-1). Cytokines cause cartilage degeneration, and increase the vicious cycle of inflammation (inflammation-cytokine production-cartilage damage- more inflammation-more cytokines-more cartilage damage etc.). This obviously promotes degenerative joint disease (DJD) and decreased performance.

IRAP blocks the receptor sites in the joint that react when IL-1 comes into contact: it keeps the Interleukin from being recognized and causing further damage to the cartilage, breaking the cycle. (Hence the name “Interleukin Receptor Antagonist Protein”.) Less inflammation equals less discomfort and freer movement. Decreased joint capsule irritation allows production of better quality fluid, which we see on repeated injections.


Horses that have a specific joint with DJD that has not responded well to intra-articular HA/cortisone or other treatments are potentially great candidates for IRAP treatment. Early inflammation causing lameness (demonstrated by a distended joint capsule, heat, and discomfort to flexion) can be quieted with IRAP and appropriate rest. Ask us if IRAP may be beneficial for your horse.


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