Recurrent airway obstruction (RAO) is a common respiratory disease of horses characterized by bronchoconstriction, mucus production, and bronchospasm. Pulmonary hypertension is known to occur secondary to recurrent airway obstruction in horses. The development of pulmonary hypertension in RAO-affected horses is well-documented, however, it is not known how rapidly increases in pulmonary artery pressure occur after the onset of RAO.¹ The subsequent changes in the pulmonary arteries accompanying this syndrome can lead to heart failure.

Pulmonary hypertension involves thickening of the pulmonary arteries and an associated increase in blood pressure. While this has been a well-documented finding in humans with severe asthma, until recently, it had not been detected in horses. Severe equine asthma or RAO is characterized by airway inflammation, coughing and labored breathing. The condition is usually triggered by dust and mold in hay and other environmental factors.

RAO-induced pulmonary hypertension is also thought to be a factor in exercise-induced pulmonary hemorrhage (EIPH), whose incidence in racehorses is very high. Based on airway endoscopic examination, it is reported that >75% of racing Thoroughbreds experience EIPH.²

NOTE: The Association of Racing Commissioners International Uniform Classification Guidelines for Foreign Substances has designated Sildenafil Citrate a CLASS 3 DRUG. It is illegal in horse racing due to the fact that it increases cardiac output and can boost a race horse’s performance.

Where to buy Sildenafil Citrate 

Sildenafil Citrate is available in the U.S. through pharmaceutical manufacturers and through veterinary custom compounding companies. 

Sildenafil Citrate carries numerous 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.

¹equusmagazine.com.

²Manohar, M., Goetz, T. L -NAME does not affect exercise-induced pulmonary hypertension in Thoroughbred horses. Journal American Physiological Society, 8750-7587/98 1998.