Bone Mineral Density and Metacarpophalangeal Joint Pathology Are Associated with Exercise but Not Proximal Sesamoid Bone Fracture in Thoroughbred Racehorses

Introduction: Triamcinolone (TA) is a frequently used corticosteroid in horses and people, and epidural steroid injection is common in people. The objectives of this study were to investigate and compare pharmacokinetics and pharmacodynamics of epidural and intramuscular (IM) triamcinolone.

Materials and Methods: Six horses with chronic, Grade ⅗ (AAEP) lameness received intramuscular and caudal epidural injection of TA (18 mg) in a crossover study design with a 60-day washout period. Blood samples were collected, and lameness examinations performed (0–60 days pre/post treatment). CSF (C1-C2 centesis) collected 24 hours post treatment and blood samples were analysed with liquid chromatography-mass spectrometry. Data was analysed with mixed-effect ANOVA and t-tests, with p <0.05 considered significant.

Results: Maximum plasma TA concentration was higher (p = 0.001) after epidural (1.38 ± 0.71 ng/mL; 12 ± 0 hours) than IM injection (0.27 ± 0.11 ng/mL; 22 ± 9 hours). Overall drug exposure (AUC) was higher (p = 0.02) and half-life was longer (p = 0.004) with IM (121.9 ± 97.4 hours ng/mL and 561 ± 705.4 hours, respectively) compared with epidural (55.3 ± 12.2 hours ng/mL and 45.9 ± 26.6 hours, respectively) injection. CSF TA concentration was higher (p = 0.003) at 24 hours post epidural (0.20 ± 0.07 ng/mL) than IM (0.05 ± 0.02 ng/mL) injection. Lameness was not improved with either treatment (p = 0.34 and 0.28).

Discussion/Conclusion: Higher TA CSF concentration may indicate epidural TA is a viable treatment option for spine-related issues in horses, including vertebral articular facet pain.

Acknowledgements: The study is supported through a Tennessee Equine Veterinary Research Organization Grant.

Publication History

Article published online:
26 October 2022