By Dr. Allison Hartman

If you missed Part 1 of our blog series on EGUS, you can find it here. 

Let’s say you’ve just indulged in a rich gourmet meal complete with red wine and a decadent chocolate dessert.  An hour or so later, you’re regretting that decision as some pesky heartburn keeps you awake.  Eventually you swallow some Tums©, Tagamet©, Zantac© or even Nexium© and breathe a sigh of relief as those clinical signs abate and you drift off to sleep.

Believe it or not, many of the medications we use to treat our own heartburn work on horses as well.  The goal of EGUS therapy is not to treat the ulcer itself, but to decrease the acidity of the horse’s stomach to allow its natural healing mechanisms the opportunity to repair the damaged mucosal lining.

Image Courtesy SmartPak Equine

Image Courtesy SmartPak Equine

Omeprazole (Proton Pump Inhibitors)

The gold standard in the treatment of EGUS is omeprazole, sold under the trade name Gastroguard©.  This product stops the production of gastric acid at the immediate source, and is known in the chemical world as a proton pump inhibitor (PPI).  By stopping the production of gastric acid, the mucosal lining of the stomach is allowed to heal, which can take anywhere from a couple days to multiple weeks, depending upon the size, severity and location of the ulcer within the stomach.

UlcerGuard© is another omeprazole product, given at a quarter of the dose of Gastroguard©, and utilized in the prevention of gastric ulcers.  Both of these products are given once a day, and elicit the best response when given in the morning on a minimally full stomach.  They are most effective in the first eight hours after administration.

It must be noted that long term use of PPIs has been shown to impair the digestion of protein, an integral component to a horse’s nutritional demands.  PPIs are safe for use up to 90 days (so your 2-4 weeks of therapy is perfectly safe) but relying on them for longer periods of time is not recommended.

Rebound Acid Hypersecretion and PPIs

While discussing the use of PPIs, it is paramount to understand the process of rebound acid hypersecretion.  Long term use of PPIs followed by abrupt discontinuation of therapy has been shown to cause a consistent increase in gastric acid production, often worse than the initial condition prior to therapy.  When using PPIs, it is important to wean the horse off medication using progressively lower doses over the course of 10 days.

It is worth noting that there are several studies demonstrating the beneficial effects of using the nutraceutical sea buckthorn, in the prevention of rebound acid hypersecretion.  From personal experience, I have had the best effects incorporating sea buckthorn into my horse’s treatment regimen at the initiation of the omeprazole weaning period, if not before.

H2-receptor Antagonists

Ranitidine (Zantac©) and cimetidine (Tagamet©) have also been used routinely in the prevention and treatment of gastric ulcers.  Both drugs are considered H2 receptor antagonists, or H2 blockers.  Where omeprazole prevents the production of gastric acid directly at the source, H2 blockers are one step removed from that process and prevent the H2 signaling molecule (histamine) from binding to the receptor which activates the production of gastric acid.

Sounds complicated, right?  My goal in providing readers with such information is not to overwhelm you, but instead, to illustrate why veterinarians consistently turn to omeprazole when faced with EGUS; it halts the production of acid at the source and has a longer duration of efficacy compared to H2 blockers.  In some situations, weeks of omeprazole therapy are not a viable, financial option for clients, so we may turn to the H2 blockers to help achieve similar results in the reduction of clinical symptoms associated with EGUS.  For the best efficacy, H2-blockers must be given three times a day, making them slightly more challenging from a management perspective.

Sucralfate

Sucralfate is another product occasionally used as a protective agent in horses with ulcers located in the glandular region of the stomach.  When exposed to such acidic environments, this fluid is converted into a sticky substance which coats the lining of the stomach and binds to preexisting ulcerations to form a protective barrier.  This product must be given on an empty stomach (which we try to avoid in horses with EGUS) and may prevent the uptake of other drugs administered simultaneously.  While effective, the large size of the dose and the duration of therapeutic programs often makes this product cost prohibitive.

Stay tuned for Part 3 of Dr. Hartman’s blog regarding the management of horses with EGUS!