Duration of antisecretory effects of oral omeprazole in horses with chronic gastric cannulae

Abstract

Summary Eight female horses with chronic gastric cannulae were given omeprazole as enteric‐coated granules (1.4 mg/kg bwt) via nasogastric tube once daily for 6 days. The effects on basal and pentagastrin‐stimulated gastric acid secretion were determined 5 h after dosing on Days 1 and 5 ofadministration. A third gastric secretion test was done on Day 7, 24 h after the dose on Day 6. Gastric juice volume, pH, acidity, and acid output were determined during a 1‐h basal secretion test followed by a 2‐h pentagastrin‐stimulated (6 μg kg −1 h −1 ) test. When compared with placebo controls, omeprazole significantly inhibited basal gastric acid output by 72% and pentagastrin‐stimulated acid output by 86% on Day 5. Gastric juice pH was also significantly increased. On Day 7, basal gastric acid output was significantly decreased by 90% and pentagastrin‐stimulated secretion was decreased by 72%. The effect of omeprazole administration on gastric juice volume was variable. Once daily administration of 1.4 mg omeprazole/kg bwt significantly inhibited basal and stimulated gastric acid secretion in horses by the 5th dose. Gastric acid secretion was significantly inhibited for at least 27 h after omeprazole treatment, indicating a long duration of antisecretory effect of the drug in horses.