Contrary to popular belief, not all chronic equine gastric disease syndromes are alike, nor do they arise from the same causes. In 2015 researchers split the condition into two categories—equine glandular gastric disease (EGGD) and equine squamous gastric disease (ESGD)—because of each condition’s distinct pathology, risk factors, diagnostics, and treatment approaches.1

The horse’s stomach is divided into two discrete regions:

• The esophageal or non-glandular region

• The glandular region

The esophageal region (squamous mucosa) covers approximately one-third of the equine stomach, is devoid of glands, and is covered by stratified squamous epithelium similar to the esophagus. The glandular region covers the remaining two-thirds of the stomach and contains glands that secrete hydrochloric acid, pepsin, bicarbonate and mucus. A sharp demarcation (margo plicatus or cuticular ridge) separates the squamous mucosa from the glandular mucosa.2

Dynamics of Gastric Ulcerative Disease in Horses

The horse’s stomach continuously secretes variable amounts of hydrochloric acid throughout the day and night and secretion of acid occurs without the presence of feed material. Foals secrete gastric acid as early as two days of age, and acidity of the gastric fluid is quite high, which may predispose foals to equine squamous gastric disease. ESGD affects the upper squamous region of the horse’s stomach, which is unprotected from gastric acid. 

Equine glandular gastric disease involves the stomach’s lower region. Its prevalence depends on the horse’s breed and lifestyle, but the literature suggests ranges from about 10% to 65%. Incidence of ESGD is higher among Warmbloods and sport horses, at around 46% to 65%. In preliminary findings from one study, exercise frequency and performance level were associated with an increased risk of EGGD in show jumping Warmbloods, while feeding and exercise factors seem to contribute to increased risk of EGGD in Thoroughbred racehorses.2

Treatment of Gastric Ulcerative Disease in Horses

After confirming EGGD (usually via gastroscopy), omeprazole is usually the standard method of treatment. However, the literature holds that glandular disease tends to be more challenging to treat than squamous. While the reason for this disparity is unknown, diet and duration of fasting prior to omeprazole administration may impact the drug’s pharmacokinetics and pharmacodynamics.2

One study suggested adding the protectant sucralfate to the omeprazole treatment after observing a 65% healing rate when combining the two drugs, while another study suggested that misoprostol alone might be more effective than omeprazole plus sucralfate.1 Researchers have also tried EGGD with antimicrobials (such as trimethoprim-sulfadimidine) and dietary supplements containing polysaccharides.  

Other pharmacologic effects of misoprostol include increased amplitude and frequency of uterine contractions, cervical thinning and relaxation, stimulation of uterine bleeding, and total or partial expulsion of uterine contents in pregnant animals.

Misoprostol Contraindications & Warnings

In horses, a study4 in midgestational pregnant mares given a 5-day course of oral misoprostol 5 µg/kg PO twice daily as a GI mucosal cytoprotectant during colic found that pregnancy was not disrupted and no adverse effects were noted. Cervical tone, ultrasonographic characteristics of the uterus, cervix and conceptus, and progesterone and estrone sulfate concentrations were similar before misoprostol treatment.

In humans, misoprostol in oral or vaginal form is an established method of labor induction. Its use after previous caesarean section is associated with a high rate of uterine rupture; according to international guidelines it is therefore contraindicated in this setting.5

The National Institute for Occupational Safety and Health (NIOSH) classifies misoprostol as a hazardous drug. Personal protective equipment (PPE) should be used accordingly to minimize the risk for exposure.

Where to buy Misoprostol

Misoprostol is available in the U.S. through several pharmaceutical manufacturers and through veterinary custom compounding companies. 

Please consult your veterinarian prior to beginning any treatment regimen.

FOR RX ONLY: A valid prescription from a licensed veterinarian is required for dispensing this medication.

1Haggett, E. Equine gastric ulcer syndrome in foals, UK-Vet Equine, 0.12968/ukve.2020.4.4.98, 4, 4, (98-101), (2020).

2Bezdekova, B., Wohlsein, P., Venner, M. Chronic severe pyloric lesions in horses: 47 cases, Equine Veterinary Journal, 10.1111/evj.13157, 52, 2, (200-204), (2019).

4Jacobson CC, Sertich PL, McDonnell SM. Mid-gestation pregnancy is not disrupted by a 5-day gastrointestinal mucosal cytoprotectant oral regimen of misoprostol. Equine Veterinary Journal. 2013;45(1):91-93.

5Rath W, Tsikouras P. Misoprostol for Labour Induction after Previous Caesarean Section - Forever a "No Go"?. Geburtshilfe Frauenheilkd. 2015;75(11):1140-1147. doi:10.1055/s-0035-1558171.