Evaluating Ulcer Medications

Studies have shown that gastric squamous (the non-glandular area of the stomach) ulcers affect approximately 80-95% of racehorses, and more than half of the entire domestic horse population. A recent study from Murdoch University in Australia determined that omeprazole (a proton-pump blocker) is more effective than ranitidine (a histamine inhibitor) when treating gastic squamous ulcers in racehorses. The study was published in the Nov. 15, 2005, edition of the Journal of the American Veterinary Medical Association.

Gastric ulcers can induce pain and mild colic in horses, which can hinder their performance. Gastric squamous ulcers, the most common form of ulceration, cause a break or erosion in the stomach lining. Gastric ulcers occur in all ages and breeds of horses, but are most prevalent in foals and performance horses.

Clinical signs of gastric ulcers can include poor performance, weight loss, and mild colic. Risk factors thought to cause ulcers are feeding a high-concentrate diet, limited grazing and turnout, stall confinement, intense exercise, and stressful environments. Prolonged usage of non-steroidal analgesic medications such as Bute and Banamine can also cause ulcers in the acid-secreting glandular part of the stomach and contribute to squamous ulceration. Previous studies showed ulcers can be reduced by altering the horse's environment to eliminate or reduce risk factors. This can be difficult or unfeasible in a training situation, which is why the use of anti-acids has become widespread.

The Murdoch study examined the effects of gastric ulcer medications omeprazole (such as GastroGard) and ranitidine (Zantac) in 60 racing Thoroughbreds prescreened to have gastric squamous ulcers.

Omeprazole prevents the secretion of hydrochloric acid from the stomach by specifically blocking hydrogen (proton) transport into the gastric fluid. Acidity is related to the amount of protons (or hydrogen ions) that are present in the gastric fluid. Scientists know that acid has a direct erosive action on the squamous lining of the top of the stomach.

Ranitidine works in a different way to reduce acid production. It does so by blocking histamine signals to these acid-producing cells. Both ranitidine and omeprazole have been used to treat gastric squamous ulcers in horses.

Horses in the study were divided into three groups, and medications were administered according to label requirements. Group 1 (controls) did not receive any medication for 28 days, then got omeprazole for 28 days. Group 2 received omeprazole once a day for 28 days, then no treatment for 28 days. Group 3 received ranitidine every eight hours for 28 days, followed by four weeks of omeprazole. Horses were endoscopically evaluated on Days 0, 28, 42, and 56. Ulcers were rated on a scale from 0 (no ulcers) to 3 (severe ulceration).

"Omeprazole was more effective than ranitidine in healing gastric squamous ulcers in Thoroughbreds maintained in race training," the study concluded. "Improvement was detected by 14 days and persisted in most of the Group 2 horses for at least 28 days after omeprazole treatment was discontinued."

Researchers for this study were Guy D. Lester, BVMS, PhD, Dipl. ACVIM; Rachael L. Smith, BVSc; and Ian D. Robertson, BVSc, PhD.

About the Author

Chad Mendell

Chad Mendell is the former Managing Editor for TheHorse.com .

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