Equine athletes and old campaigners suffering from joint injuries are often given intra-articular medication to alleviate pain and discomfort, especially in high-motion joints. Generally, there is a withdrawal time period between treatment with corticosteroids and competitive performance. One study evaluated the effects of IA corticosteroid treatment on lung function in horses with severe asthma [Bessonnat, A.; Picotte, K.; Lavoie, J.P. Intra-articular triamcinolone acetonide improves lung function in horses with severe asthma. Equine Veterinary Journal 2020, vol. 52, pp. 131-135; DOI: 10.1111/evj.13128].
Triamcinolone acetonide (TA) is a preferred corticosteroid for joint treatment due to its chondroprotective effects and effective control of joint inflammation. While it remains detectable in joint fluid for as long as 15 days, it also is identifiable in the blood stream for four days, with cortisol suppression persisting for about 11 days. Previous studies have demonstrated that intramuscular injection of TA has anti-inflammatory effects on lung function for up to a month. While there might be some benefit to suppression of lung inflammation in horses with severe asthma, it is also possible that such treatment delays an accurate diagnosis and effective therapy.
The study used 10 severely asthmatic horses and of these six were supplemented with dusty hay to exacerbate their asthma. Five horses (based on random selection) received IA treatment with TA in both tarsocrural joints at a dose of 20 mg per joint to a total of 40 mg. The other five horses received one intramuscular dose of 40 mg in the semitendinosus muscle. Lung function was evaluated prior to treatment, then weekly for five weeks. Hoof tester exams were conducted on all horses each day due the laminitis potential from the high dose of TA given, i.e., approximately twice the recommended dose—no horses developed laminitis.
Both the IA and IM route of administration of TA produced similar improvements in lung function over four weeks. Initial lung improvements were greater in the IA-treated horses but persisted for a shorter duration compared to IM administration. With IA TA treatment, lung function remained improved for two weeks past when serum concentrations of TA dropped below the Association of Racing Commissioners International requirements.
The authors concluded: “Although corticosteroids are effective in the treatment of joint disease and severe equine asthma, their reported systemic side effects include the suppression of the hypothalamic–pituitary–adrenal axis after IM, IA or IV administrations, the alteration of bone metabolism after IM and IA administrations and possibly, laminitis. Considering the risk of septic arthritis associated with intra-articular injection and the high frequency (every 2–3 weeks) of injections needed to provide an improved airway function, the IA corticosteroid should not be used to treat equine asthma.”
This study illuminates the effects of IA treatment with TA on other organ systems.