Up to 90% of horses treated for gastric ulcers with omeprazole can experience a recurrence of ulcers when they stop taking this drug.

Horses can develop rebound acid hypersecretion (RAHS) after the discontinuation of omeprazole. Higher levels of stomach acid often lead to new ulcers being formed, particularly if the underlying causes of ulceration have not been addressed.

This is frustrating for both horse owners and veterinarians, leading to reduced performance and well-being in the horse. Why do so many horses experience ulcer rebound and what can be done to prevent these gastric lesions from coming back?

Some performance horses are maintained on omeprazole year-round to reduce the risk of recurrence.

But long-term omeprazole use is not advised because this drug can interfere with the digestibility and absorption of certain nutrients in the diet. Keeping a horse on omeprazole is also an expensive proposition.

Instead, you can prevent ulcer relapse in your horse by supporting their gut health, identifying risk factors, and adopting research-backed feeding and management practices.

Omeprazole for Ulcer Treatment

GastroGard, a slow-release form of omeprzole, is the only FDA-approved treatment to resolve and prevent gastric ulcers in horses. Due to the high prevalence of Equine Gastric Ulcer Syndrome (EGUS) in performance and pleasure horses, the use of this drug is widespread.

Omeprazole is a proton pump inhibitor that works by decreasing the production of stomach acid. By raising the gastric pH (lowering stomach acidity), omeprazole creates a more favourable environment to allow existing ulcers to heal.

Although omeprazole treatment is effective at resolving existing ulcers in the squamous region of the stomach, it is not a long-lasting effect. Omeprazole needs to be given continuously to inhibit the secretion of gastric juices.

Evidence of Ulcer Rebound in Horses

Several studies show a high rate of ulcer recurrence after omeprazole is stopped. [1][2][3]

These studies demonstrate that 4 mg/kg of omeprazole given daily is effective in reducing ulcer number and severity. However, when treatment is stopped, ulcers are likely to form again.

In one study, 90% of horses had a recurrence of ulcers after being taken off of the 4 mg/kg daily dose of omeprazole. [2]

To avoid this, some veterinarians recommend gradually reducing the dose to 1 or 2 mg/kg after 28 days. However, even with this strategy, 16-20% of horses develop new lesions or worsening lesions during the period of reduced omeprazole dosing. [2][4][5]

Furthermore, performance horses that are most at risk of ulcer rebound may not be able to use omeprazole continuously.

Competitions require that horses undergo a 72-hour withdrawal period from this drug prior to competition. This could be enough time for ulceration to occur. [6]

Careful attention needs to be paid to horses discontinuing omeprazole use. There are strategies you can use to reduce the risk of ulcer rebound, which we will discuss later on in this article.

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Why Do Ulcers Come Back in Horses?

This question is still an active area of research. However, the following mechanisms have been hypothesized to contribute to the high rates of ulcer recurrence in horses.

Rebound Acid Hypersecretion

After cessation of omeprazole treatment, rebound gastric hyperacidity and ulcer recurrence are common.

In human s