Misoprostol: A Better Option for Treating Equine Gastric Glandular Disease
It’s common knowledge that many horses suffer from gastric disease. What you might not know is that two distinct forms of gastric ulcers exist—equine squamous gastric disease (ESGD) and equine glandular gastric disease (EGGD)—depending on the exact location in the stomach. Researchers in the U.K. recently reported that these two diseases really shouldn’t be considered the same and, therefore, mandate different treatments. In their study they found better success treating EGGD with misoprostol than with a combination of omeprazole and sucralfate, two drugs known to effectively treat ESGD.

“While both types of disease fall under the umbrella term equine gastric ulcer syndrome, research shows that they are actually distinctive entities with different risk factors and, therefore, likely different ways of developing,” explained Gayle. D. Hallowell, VetMB, PhD, Dipl. ACVECC and ACVIM, a professor in veterinary internal medicine and critical care at the University of Nottingham.

Hallowell described how while horses with ESGD have apparent ulcerative damage to the stomach wall, horses with EGGD instead seem to have a mixed type of nonulcerative inflammation. Another example of how the two differ is that omeprazole, an oral medication proven useful for treating ESGD, doesn’t appear particularly effective for horses with EGGD.

“Omeprazole decreases the acidity of the stomach, thereby protecting the squamous or upper region of the stomach in ESGD. The fact that horses with EGGD do not respond favorably to omeprazole suggests that other factors contribute to disease, such as a breakdown of normal gastric defenses, reduced gastric blood flow, or that EGGD is an extension of inflammatory bowel disease,” Hallowell said.

To identify a more effective way of helping horses with EGGD, Hallowell and colleagues compared a combination of sucralfate and omeprazole with another medication called misoprostol.

“The rationale for using misoprostol is that it is a prostaglandin E analog that (in addition to) inhibiting gastric acid and pepsin [a digestive enzyme that breaks down proteins], it … enhances the resiliency of the wall of the stomach to injury, due to its anti-inflammatory properties and ability to increase blood flow to the stomach lining,” Hallowell shared.

She added, “Misoprostol is used in human patients with refractory glandular disease, and one equine study showed that misoprostol effectively inhibited gastric acid production in horses.”

Sucralfate reportedly physically blocks diffusion of acid into the stomach, inhibits pepsin and bile acid release, stimulates prostaglandin E synthesis, and has other beneficial effects. In fact, in one equine study researchers showed a 67.5% healing rate for glandular ulcers with a combination of sucralfate and omeprazole.

In the current study researchers administered either misoprostol or an omeprazole/sucralfate combination to 63 sport horses with glandular disease for 28-35 days. Hallowell and colleagues found that misoprostol-treated horses experienced superior healing over omeprazole/sucralfate-treated animals (72% vs. 20%) as evidenced by gastroscopic (seen with an endoscope passed into the stomach) improvement in lesions and resolution of clinical signs—primarily poor performance, girthing pain, and behavior changes.

“While these findings are encouraging, this was a small study, the clients were not blinded to their horses’ treatments, and the horses’ diets were not controlled. Not to mention that no validated EGGD gastroscopy scoring system yet exists,” said Hallowell.

A better understanding of EGGD will help veterinarians fine-tune how they use misoprostol and identify additional means of treating this frustrating condition.

The study, “Misoprostol is superior to combined omeprazole-sucralfate for the treatment of equine gastric glandular disease,” was published in the September 2019 edition of Equine Veterinary Journal. Study coauthors were Georgina Varley, Mark Bowen, Jocelyn Habershon-Butcher, and Vicki Nicholls, all from the U.K. The abstract is available free online.