An IRAP syringe, containing the treated beads


One of the newest substances that is injected to horse joints is known as IRAP®.  IRAP is an acronym, and the name says it all; here’s what it means.


A Civil War Battery of Horse Drawn Artillery

I stands for interleukin-1 (I-1). Interleukins are a group of protein molecules that are involved in the process of inflammation, and I-1 levels are increased in joint inflammation (arthritis).

R stands for receptor.  For interleukin-1 to work, it has to bind to a special receptor-site in the joint capsule that lines the joint.

A stands for antagonist. An antagonist to anything offers opposition to it.

P stands for protein. Proteins are any of a huge group of nitrogen-containing compounds that are essential components.  The protein in IRAP binds to the receptor where I-1 binds, and acts to antagonize the activity of I-1.

So, in sum, IRAP is a protein that works by binding to the receptor site on the joint capsule where the inflammatory protein interleukin-1 binds, which helps prevent interleukin-1 from contributing to joint inflammation.

A clever bit of biochemistry is responsible for IRAP.  A German biochemist found that the white blood cells that normally circulate in your horse’s


An IRAP syringe, containing the treated beads

bloodstream could be stimulated to product the IRAP protein.  To start the process, blood is drawn into a special syringe containing glass beads coated with a substance that enhances the production of anti-inflammatory proteins, including IRAP.  The syringe is then incubated for 24 hours.  Following incubation, the syringe is centrifuged, and 20 – 25 ml of IRAP serum is collected (enough for 5 – 6 doses).  The serum is filtered to weed out any bacteria, and then frozen into doses for later use.  When needed, it’s thawed, and injected into inflamed joints.

How effective is it?  Well, frankly, there’s not been a lot of published information yet, but one study in horses, as well as a study of 376 people with osteoarthritis of the knee, have each concluded that it’s an effective treatment for joint inflammation.  It can be used post-surgically, as well as in cases of osteoarthritis that aren’t responding to other treatments; it’s an option for first-line therapy as well.

IRAP® is certainly another option for treating your horse’s joints – whether or not it’s a better option is a question that still needs to be answered.  There is a big difference between treating inflammation and eliminating the cause of inflammation.  In addition, the expense of the product compared to other, more easily obtained, alternatives may limit it’s use in many cases.

One interesting possibility for therapy is that the IRAP® protein may have some effectiveness for treatment in areas other than joints.  As such, it’s been injected into and around tendons and ligaments, for example.  How effective that treatment might be is anyone’s guess, but there seems to be little potential for harm.

Bottom line?  IRAP is not likely to be harmful, it is expensive, and it is not a cure for osteoarthritis.  But, in certain cases, say, where your veterinarian is concerned about the use of corticosteroids, it is perhaps worth a try.

Print Friendly, PDF & Email
scroll to top