For the first time, researchers have demonstrated that the corticosteroid prednisolone improves the lung function of horses with recurrent airway obstruction, even in the presence of continuous exposure to antigens. The same study also revealed that a low dose of a similar drug, dexamethasone, reversed airway obstruction despite continues antigen exposure.
"Recurrent airway obstruction (RAO, heaves) is a chronic inflammatory respiratory disease of mature horses," wrote the research team from the Universite de Montreal headed by Mathilde Leclere, DVM. "Susceptible horses develop bronchoconstriction, airway inflammation, and mucus accumulation leading to airway obstruction and abnormal pulmonary function in response to environmental antigens (inhaled organic particles, such as moulds, spores, mites, endotoxins)."
Previous studies have found that corticosteroid drugs are effective in improving lung function when administered intravenously or via inhalation, but typically only if concurrent improvements in the tested horses' environments were made. The researchers sought to compare the efficacy of oral prednisolone and dexamethasone in reducing airway obstruction in horses with RAO.
Seven mature horses with RAO were moved from pasture to individual stalls inside barns, fed hay, bedded on straw, and exercised outside for only two hours per day. Using a randomized, crossover study design, the horses received 2 mg/kg prednisolone or 0.05 mg/kg body weight orally once daily for seven days.
Key findings of the study were:
- Both prednisolone and dexamethasone administration resulted in a significant improvement in lung function;
- The noted improvement was more obvious after administration of dexamethasone compared to prednisolone; and,
- In horses that received dexamethasone, lung function test results while residing in the barns were similar to lung function measurements obtained while the horses were on pasture before the study began.
According to the study, "Both corticosteroids improve pulmonary (lung) function, in spite of continuous antigen exposure. However, oral dexamethasone at 0.05 mg/kg bwt (body weight) is more effective than prednisolone at 2 mg/kg bwt in the treatment of RAO."
This is the first study to show that prednisolone is capable of improving lung function in horses with RAO.
The study, "Efficacy of oral prednisolone and dexamethasone in horses with recurrent airway obstruction in the presence of continuous antigen exposure," was published in the May 2010 edition of the Equine Veterinary Journal.
The abstract will soon be made available on PubMed.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.