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College of Veterinary Medicine
Orthopedic Research Laboratory

IRAP (Interleukin-1 Receptor Antagonist Protein)

syringe with beads

IRAP (Orthokine) is marketed by Arthrex VetSystems in the USA.  The product was originally developed in Europe, and has been used extensively in Germany. 

IRAP (Interleukin-1 Receptor Antagonist Protein) is an anti-inflammatory protein that counteracts the destructive effects of inflammatory proteins such as Interleukin-1 (IL-1) within the inflamed joint. 

Levels of IRAP and other anti-inflammatory proteins in the blood can be increased and produced for joint injection by incubating a 50ml sample of blood from your horse for 24 hours in a syringe produced by Arthrex VetSystems.  The syringe contains glass beads coated with a substance to enhance production of anti-inflammatory proteins including IRAP.  The syringe must reach the incubator as soon as possible after the blood has been harvested from your horse; though transport of the syringe for short periods of time in a water bath at 37°C has yielded satisfactory results. 

After 24 hours, the syringe is centrifuged, and the serum collected.  The amount of serum collected from each 50ml syringe of blood is usually between 20-25ml.  This yields 5-6 doses of IRAP, but the number of doses available for use from each collection is dependent on the specific joint. 

Once the serum has been harvested, it is filtered and then frozen in single dose aliquots in the ‘clean room’ at the NCSU-VTH pharmacy.  We then submit a small sample of each batch of serum for microbial culture to ensure to the best of our ability that that product that is released for joint injection is sterile.   Injections are released for use 8 days after original blood collection.  Injections are kept frozen until immediately before use, and if necessary can be shipped frozen to your veterinarian.  Once thawed and immediately before they are used, each individual dose is again sterile filtered.

Indications for use of IRAP/Orthokine in the joint include horses with a well defined synovitis/capsulitis, particularly those horses that do not respond well to conventional anti-inflammatory joint medication and horses that have had arthroscopic surgery and have been found to have focal cartilage diseases. 

Orthokine is NOT recommended for use in tendon sheaths or bursae, in joints where there are bone fragments, fractures, meniscal or ligamentous injury unless it has been successfully treated arthroscopically, in bone cysts, or in horses with advanced osteoarthritis (low success rate). 

In general 2-3 treatments of the joint are performed, at 8-14 day intervals.  The volume injected at each treatment is 1-8ml, depending on the joint.  First injection after surgery may be given at 7 days. 

After injection, we routinely bandage the joint if possible for 2 days, and the horse should be kept on 3 days of strict stall rest, followed by 10 days of hand-walking (30-45 minutes).  Once the course of injections and the final hand-walking period is completed, horses should receive one week of ridden walk exercise, followed by one week of ridden walk and trot, before returning gradually to regular training programs. 

Exact exercise instructions will be provided by your treating veterinarian, as the instructions above may vary, depending on the primary joint disease.

Obviously, as with any joint injection, the joint should be monitored carefully for any signs of infection (heat, swelling, increase in lameness) – if you notice any of these signs, please contact your veterinarian immediately.

Adverse effects of this product have not been reported after extensive use in people and horses in Europe, though if you have any concerns about your horse after injection you should contact your veterinarian.

IRAP blood collection is performed on Monday and Wednesday mornings at NCSU-VTH. Appointments must be scheduled through the Equine Orthopedics Service.


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NC State College of Veterinary Medicine
Equine Orthopedic Research Laboratory
4700 Hillsborough Street
Raleigh, NC 27606