The debilitating respiratory syndrome often known as heaves or recurrent airway obstruction (RAO) is a common but serious problem for those who own and manage horses. Horses that live in barns, stables or outdoors—essentially all domesticated horses—are typically exposed to high levels of pollens, molds and other particulates, which puts them at an increased risk of developing this condition.

These terms fall under the umbrella of “equine asthma,” a performance-limiting, respiratory disease that affects horses with long-term exposure or excessive sensitivity to particulates. This is distinguished from the less severe form of equine asthma, known as Inflammatory Airway Disease (IAD), a much more common and potentially curable malady.¹Conversely, RAO can often be effectively treated, but is not said to be curable. 

The chief clinical sign distinguishing RAO from IAD is clearly recognizable episodes of respiratory distress. Here, a horse will appear to be struggling with the effort to breathe; these episodes are usually transitory until the horse becomes severely affected. 

The most common clinical signs of RAO are:

• Chronic cough
• Nasal discharge
• Exercise intolerance
• Respiratory difficulty

Horses with RAO often appear normal at rest, but can have an increased respiratory rate and/or cough. When coughing is the prevalent symptom, a “heave line” will frequently be seen along the bottom edge of the ribs, caused by abdominal muscles which enlarge due to the excess work associated with breathing.

Forms of Recurrent Airway Obstruction

There are two forms of RAO. The first is the type associated with stalled horses; the second is summer pasture-associated recurrent airway obstruction (SPARAO).¹ The latter is most commonly seen in horses that live on pasture and come in contact with high levels of airborne mold spores. Winter is usually the most common season for heightened symptoms of barn-associated RAO in the northern U.S., while the most prevalent signs of pasture-associated heaves happen in the Spring and early Winter in the north, and in summer and early fall in the south.

Albuterol Sulfate for RAO in Horses

Albuterol is a β-adrenergic agonist used in horses for its effects on bronchial smooth muscle to alleviate bronchospasm or cough. Inhalation aerosol formulations have been used to improve hypoxemia in anesthetized horses, however, in normal horses, albuterol does not appear to affect physiologic responses to exercise.²

Albuterol sulfate is a synthetic sympathomimetic amine which occurs as a white crystalline powder.² This is the version of albuterol produced for oral administration. It is a sympathomimetic drug that preferentially stimulates β2-adrenergic receptors found primarily in vascular smooth muscle (including bronchial, GI, and uterine tissues) to cause relaxation of bronchial smooth muscle, reduced airway resistance, vasodilation, and tocolysis, as well as to inhibit release of bronchoconstrictive mediators from mast cells. At recommended doses, albuterol spares the β1 receptor found primarily in the heart, thus lowering the likelihood for cardiac adverse effects.²

Albuterol sulfate is contraindicated in horses that are hypersensitive to it or to other sympathomimetics. Most side effects are dose-related and are consistent with other sympathomimetic agents.

Where to buy Albuterol Sulfate

Albuterol sulfate is available in the U.S. through pharmaceutical manufacturers and through veterinary custom compounding companies. ALBUTEROL SULFATE 10 MG/SCOOP, ORAL POWDER, 100 SCOOPS (5CC SCOOP) by NexGen Pharmaceuticals is indicated for the management of recurrent airway obstruction (RAO) in horses.

This product carries several potential drug interactions. Please consult your veterinarian prior to beginning any treatment regimen.

FOR RX ONLY: A valid prescription from a licensed veterinarian is required for dispensing this medication.

¹Derksen FJ, Olszewski MA, Robinson NE, Berney C, Hakala JE, Matson CJ, Ruth DT. Aerosolized albuterol sulfate used as a bronchodilator in horses with recurrent airway obstruction. Am J Vet Res. 1999 Jun; 60(6): 689-93.

²Plumb’s Veterinary Drugs.