It is reported that exercise intolerance might be the only clinical sign in 80% of horses affected by lower airway inflammation in their first year of training. Equine asthma is often treated with corticosteroids. Sporthorses and racehorses also often receive intra-articular (IA) injections with corticosteroids to manage joint injuries. While the medication localizes well within the joints, it diffuses out of the joints to further exert systemic anti-inflammatory effects.
A recent study evaluated the effects of IA and IM triamcinolone (TA) on lung function in 10 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 Apr 2019; 10.1111/evj.13128].
Twice the recommended intra-articular dose (40 mg) of TA was used in all horses—20 mg in each tarsocrural joint of five horses or 40 mg IM in the other five horses. Both methods of administration yielded positive results for lung function, including:
- Lung improvement occurred by Day 7 from IA injection and by Day 14 for IM injection.
- The effect of IA TA was more pronounced than the IM administration but lasted for a shorter duration.
- Lung function improved for 21-28 days in both IA and IM groups.
TA was detectable in serum in both groups by Day 3, with serum TA greater in the IA group than the IM group at that time. By Day 7, the IA route of administration yielded a serum concentration of TA that fell below the quantification threshold (100 pg/ml) used by the International Association of Racing Commissioners.
While this study focused on horses with severe asthma, the researchers cautioned: “Intra-articular corticosteroids could delay the diagnosis and implementation of appropriate therapy for horses with exercise intolerance due to mild/moderate asthma."