Current options for managing horses with severe asthma include making changes to the horse’s environment and treating with bronchodilators and corticosteroids—the latter of which are the most effective drugs but often come with negative side effects such as cortisol suppression (cortisol is a hormone that regulates important body processes). So researchers recently evaluated a potentially safer corticosteroid—ciclesonide—and saw promising results.
Mathilde Leclere, DVM, PhD, Dipl. ACVIM, associate professor in equine internal medicine at the University of Montreal, presented data from a series of studies conducted by Jean-Pierre Lavoie, DVM, Dipl. ACVIM, of the university’s Equine Asthma Research Lab, at the 65th Annual American Association of Equine Practitioners Convention, held Dec. 7-11 in Denver, Colorado.
Ciclesonide has unique pharmacological properties that make it active in the lungs, with little absorption into the bloodstream and few effects on other organs.
“Ciclesonide allows for higher dosage with fewer side effects and a favorable safety profile,” Leclere said.
The team performed three controlled studies over three years, each on eight horses with severe asthma that were exposed to a high-allergen environment (via a moldy hay challenge). In each study the groups of horses received different doses of ciclesonide via soft mist inhaler for two weeks. Horses also received dexamethasone as positive control (in other words, to compare against a corticosteroid with known efficacy and side effects) in the first two studies and a placebo in the third. The researchers assessed the horses’ lung function, clinical scores such as cough and respiratory effort, and serum cortisol levels during each two-week period.
Study 1 The researchers administered small doses of ciclesonide (450-1,800 μg twice a day) and found it neither had a negative effect on horses’ serum cortisol nor a significant effect on their clinical signs or lung function.
Study 2 Next, the team administered higher doses and found that all doses improved the horses’ lung function and clinical scores by Day 7. The horses’ lung function was nearly normal by Day 14 with the highest dose of 2,700 μg. The drug did not affect serum cortisol.
Study 3 Lastly, the researchers compared the safety and efficacy of administering 2,700 μg of ciclesonide twice a day vs. 3,712.5 μg once daily (morning or evening). The twice-a-day 2,700-μg dose improved lung function by Day 7 and once-a-day 3,712.5 μg improved function by Day 14. Again, even at higher doses, the drug had no effect on cortisol or blood parameters measured (white cell count, biochemistry).
The researchers concluded that ciclesonide does reverse airway obstruction in horses with severe asthma, and it’s the only corticosteroid to date that is not associated with cortisol suppression. It appears to be safe and is most effective when administered at 2,700 μg twice a day.