Veterinarians regularly use intra-articular (IA) corticosteroids in equine athletes to control joint inflammation. The aim of this cross-over randomized trial was to utilize an acute synovitis inflammation model to determine the residual effects of IA betamethasone and triamcinolone acetonide on various inflammatory parameters and lameness.
The study randomly allocated five mixed-breed 2-year-old horses to an IA treatment of the radiocarpal joint with 9 mg of either betamethasone or triamcinolone acetonide. Two weeks following treatment, researchers injected horses with 1μg of lipopolysaccharide (LPS) diluted in 1 mL of saline. Following LPS injection, researchers crossed the horses over and repeated both sets of injections. Researchers collected blood samples at multiple time points for mRNA analysis, as well as serum amyloid A (SAA) and cortisol concentration determination. At each time point, they also subjectively scored lameness. They also conducted additional injections with saline-only or LPS-only (twice) as negative and positive controls, respectively.
Corticosteroid-only treatment results in significant mRNA expression differences. It also results in significant and prolonged cortisol suppression. Following LPS injection, triamcinolone had a residual treatment effect evidenced by a significant treatment effect on IL-6 and PTGS1 (cyclooxygenase-1), lameness, SAA, and cortisol concentrations. Betamethasone only affected IL-6 expression.
Bottom Line About IA Corticosteroids in Equines
The commonly used intra-articular corticosteroid triamcinolone acetonide has residual anti-inflammatory effects two weeks after administration. Within the context of current racing and competition requirements, this would suggest that 14 days might not be long enough if the concern is that the drug could maintain performance-enhancing effects via its anti-inflammatory properties. Additionally, administration of IA corticosteroids in equines is not without risk. This was evidenced by significant suppression of serum cortisol. So, veterinarians and owners should weight the benefits of their administration against those risks.
