Giving Omeprazole for Ulcers Intravenously

In the past few years, we've been hearing how many more horses have gastric ulcers than we used to think. We also know that oral omeprazole paste (GastroGard, manufactured by Merial Limited, Decatur, Ga.) effectively treats and prevents ulcers. But what about horses that can't take an oral paste (such as those with gastric reflux)? How do you manage their ulcers?

At the 2007 American Association of Equine Practitioners Convention, held Dec. 1-5 in Orlando, Fla., Frank M. Andrews, DVM, MS, Dipl. ACVIM, professor and section chief of the College of Veterinary Medicine at the University of Tennessee, presented the results of a study evaluating the efficacy of an intravenous (IV) formulation of omeprazole.

He began by noting that omeprazole (GastroGard) is approved by the FDA for oral administration. Since you cannot give the oral paste intravenously, a compounded formulation (omeprazole powder reconstituted with sterile water) is needed in those horses that can't be given the oral paste. Thus, IV omeprazole should only be used when oral administration is contraindicated because of illness.

Omeprazole combats ulcers by decreasing the acidity of gastric juices (raising the pH). In humans, erosive esophagitis (inflammation of the esophagus) heals better when stomach pH is over 4.0; this was the target pH of this study. Veterinarians scoped six mixed-breed mares to view ulcers and collect gastric juices at the beginning of the study, before and after the first treatment of IV omeprazole, and twice on Day 5 (right before and one hour after the fifth and last daily dose). All six horses had ulcers in the upper nonglandular portion of the stomach, and two had ulcers in the lower glandular part of the stomach at the start of the study.

Intravenous omeprazole was not effective at raising pH above 4.0 in all mares one hour after the first injection (only three mares were over 4.0 at that time). The average pH change was from 2.01 to 4.35 in that first hour. But on Day 5, five of the mares were over 4.0 before the daily dose and all six were over 4.0 after it (an average increase of 5.27 to 7.0). In addition, nonglandular ulcer number score decreased significantly, from an average of 3.2 on Day 1 to 2.0 on Day 5.

"Intravenous administration of omeprazole (0.5 mg/kg) causes a rapid increase in gastric juice pH and has a long duration of action," Andrews concluded. "An initial IV loading dose (1.0 mg/kg) may be needed to achieve gastric juice pH of greater than 4.0 in horses with equine gastric ulcer syndrome."

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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