Anyone who’s ever managed a horse with a breathing problem knows how heartbreaking it can be to watch the animal struggle to breathe. Equine recurrent airway obstruction (RAO, also known as heaves or equine asthma) is a respiratory disease similar to asthma in humans.

Moldy hay, dust, or other allergens are known triggers of RAO, and the best way to treat the problem long-term is through proper environmental management and with medical intervention when necessary. Veterinarians commonly prescribe the bronchodilator albuterol to affected horses; the aerosol form acts within about 5 minutes to relax the airway’s smooth muscles and open the breathing passage. However, the effects typically only last about 60 minutes.

Levalbuterol is a molecule that is part of the chemical make-up of albuterol and is responsible for its bronchodilatory effects. Physicians use levalbuterol in human medicine. It has a longer duration of action compared to albuterol, but its effects are not well-understood in horses. As such, Laurent Couëtil, DVM, PhD, Dipl. ACVIM, and colleagues at Purdue University sought to determine if levalbuterol had better or longer lasting effects compared to albuterol in horses.

The researchers employed nine horses that each received treatment with albuterol or levalbuterol via nebulizer. The magnitude of bronchodilation was the same between the two treatments. The effects lasted 60 minutes with albuterol and 120 minutes with levalbuterol