"Gastric ulcers are a widespread and significant problem," said Gary W. White, DVM, of Salisaw Equine Clinic in Salisaw, Okla., at the 2003 American Association of Equine Practitioners' convention. "Omeprazole (Gastrogard) is FDA-approved for the treatment of gastric ulcers in horses and foals greater than four weeks old at 4 mg/kg/day," he said, adding that reports had suggested that doses lower than 2 mg/kg/day (a dose already proven to prevent recurrence of ulcers) might be effective in preventing the development of gastric ulcers.

White and 10 other veterinarians from private and university equine hospitals in the United States and Canada investigated whether a dose of 1 mg/kg/day would prevent occurrence and recurrence of gastric ulcers in racehorses. A total of 285 horses (including Thoroughbreds, Quarter Horses, and Standardbreds) were used to confirm the dose required to stave off ulcer occurrence and prevent recurrence. "The dorsal portion of the stomach becomes highly acidic during exercise," said White. "During the study period, these horses were maintained in active race training and were allowed to race, so that they were maintained under strong ulcerogenic conditions."

Prevention of equine gastric ulcer syndrome (EGUS) was evaluated in confirmed ulcer-free horses which were going into race training. Horses already racing or in race training with ulcers were evaluated after they underwent omeprazole treatment at 4 mg/kg/day for 28 days (the dose shown to heal ulcers) to find out the prevention of recurrence with omeprazole. All horses were scoped and their stomach linings were graded before prevention treatments (as a baseline) and again after 28-30 days of preventive treatments.

To select the dose, veterinarians compared the effects of orally administered omeprazole paste and a sham-dose (an empty tube used in the control group) at 0.5, 1.0, or 2.0 mg/kg/day for 28 days. In these trials, they found that the 1.0 mg/kg/day dose of omeprazole was more effective in preventing recurrence of ulcers than either the sham or 0.5 mg/kg/day doses. In the prevention of the occurrence of ulcers, the 1.0 mg/kg/day dose was more effective than the sham dose, and the effect did not differ significantly from the 2.0 mg/kg/day dose