SerpApi.Org
Omeprazole, one of the most widely used medications in Thoroughbred racing, may be associated with an increased likelihood of detecting exercise-induced pulmonary hemorrhage (EIPH), according to a new study published in theJournal of the American Veterinary Medical Association.
Researchers analyzed veterinary, training, and racing records from 2,924 Thoroughbreds competing in Hong Kong during the 2012-13 and 2022-23 racing seasons. While they found no evidence that cumulative omeprazole use increased the risk of fractures or atrial fibrillation, horses receiving larger cumulative doses over the previous 30 days were more likely to be diagnosed with EIPH.
Omeprazole is commonly prescribed to treat equine gastric ulcer syndrome and is also widely used as a preventive treatment in horses, often without endoscopic confirmation of ulcers. Although generally considered safe, the authors noted that relatively little research has examined the long-term effects of repeated administration in racing Thoroughbreds.
Unlike the United States, where horses may receive a variety of commercial and compounded omeprazole products, the Hong Kong Jockey Club was the sole permitted source of the medication. That allowed researchers to calculate cumulative doses from centralized prescription records, providing a more consistent measure of exposure across the study population.
For every additional 10 grams of omeprazole administered over the preceding 30 days, the hazard of detecting EIPH increased by an estimated 8 percent, according to the study's statistical model. The researchers also estimated that if the association reflects a true cause-and-effect relationship – something this study cannot establish – approximately 11 percent of EIPH cases in the study population could be attributed to omeprazole exposure.
The study found a similar trend for epistaxis, the visible form of pulmonary bleeding in which blood exits through the nostrils, although that association did not reach statistical significance. Meanwhile, no meaningful association was identified between cumulative omeprazole administration and either fractures or atrial fibrillation.
The biological explanation for the association remains unclear, the authors said. While previous research has suggested that omeprazole could affect blood vessel function, the authors emphasized that any such mechanism remains speculative and will require further study in horses.
The authors cautioned that the study cannot establish that omeprazole causes EIPH. Because it was an observational study, other factors – including why individual horses were prescribed omeprazole in the first place – could have influenced the results. The researchers also noted they did not have information on whether horses actually had gastric ulcers, since gastroscopy was not routinely performed before treatment.
Even so, the authors concluded the findings support "careful consideration of the indication and duration of omeprazole use in racehorses" and underscore the need for prospective studies examining the drug's effects on the respiratory system.
