Effects of orally administered enteric-coated omeprazole on gastric acid secretion in horses

Objectives-To determine the effects of orally administered omeprazole, as e nteric-coated capsules, on baseline and stimulated gastric acid secretion i n horses. Animals-5 healthy 8-year-old mixed-breed horses fitted with gastric cannula s. Procedure-Enteric-coated granules of omeprazole were mixed with corn syrup and administered orally once daily for 5 consecutive days. On days 1 and 5 beginning 5 hours after omeprazole administration, 4 gastric fluid samples were collected, each for 15 minutes, via the gastric cannula (baseline samp les). Pentagastrin was administered IV as a constant infusion for the subse quent 2 hours, and 15-minute gastric fluid samples were again collected (st imulated samples). Fluid volume, acidity (mmol H+/L), and pH and gastric ac id production (mmol H+) were determined for all baseline samples and for st imulated samples collected during the second hour of pentagastrin infusion. Control experiments were done in a similar manner after giving corn syrup alone to the same horses. Results-Compared with values obtained during control experiments, baseline and stimulated gastric fluid acidity and gastric acid production significan tly decreased, and the mean pH of gastric fluid samples significantly incre ased, after horses were given 5 daily doses of omeprazole. Conclusions and Clinical Relevance-Enteric-coated omeprazole (1.0 mg/kg of body weight; PO) administered once daily for 5 days significantly inhibited unstimulated and pentagastrin-stimulated gastric acid secretion in horses. This commercially available formulation of omeprazole may be efficacious i n the treatment of gastroduodenal ulcers in horses.