Can Omeprazole Prevent Gastric Ulcers in Performance Horses? What the Evidence Shows

Gastric ulcers remain one of the most common health concerns affecting horses in training. Intense exercise altered feeding schedules, transportation, and management practices can all contribute to the development of Equine Gastric Ulcer Syndrome (EGUS). While treatment options are well established, an important clinical question remains: can gastric ulcers be prevented before they occur? 

Current evidence suggests that omeprazole prophylaxis plays a significant role in reducing the risk of squamous gastric ulceration in horses undergoing training¹. 

The High Risk of Ulcers in Horses in Training 

Research has consistently demonstrated that horses in active training are highly susceptible to gastric ulcer development. In a meta-analysis evaluating multiple randomized controlled trials, approximately 77% of horses that received no preventive treatment developed gastric ulcers. In contrast, only 23% of horses receiving prophylactic omeprazole developed ulceration¹. 

These findings highlight the substantial ulcer burden associated with training environments and emphasize the importance of preventive strategies. 

How Effective Is Omeprazole? 

Omeprazole belongs to the class of drugs known as proton pump inhibitors (PPIs). By suppressing gastric acid secretion, it helps protect the squamous mucosa from acid-induced injury. 

A 70% relative risk reduction in the development of squamous gastric ulcers among horses with no previous history of ulceration when treated prophylactically with omeprazole was reported¹. 

The benefit was even greater in horses with a prior history of ulcers. In these animals, prophylactic treatment resulted in an 87% reduction in the risk of ulcer recurrence¹. 

Researchers suggested that horses with a history of ulceration may either receive longer treatment durations or possess an increased predisposition to gastric acid-related disease, making them particularly responsive to acid-suppressive therapy. 

What Dose Works Best? 

One of the most clinically relevant findings of the review was that lower prophylactic doses appeared highly effective. 

Studies included doses ranging from 0.5 mg/kg to 4 mg/kg, but the preventive efficacy of 1 mg/kg and 2 mg/kg dosages was remarkably similar. The risk ratios for ulcer prevention were 0.26 and 0.22, respectively, indicating comparable protection against ulcer development¹. 

These findings raise important questions regarding the optimal preventive dose. Lower doses could potentially reduce treatment costs while maintaining clinical effectiveness. 

Although some studies have suggested that ultra-low-dose omeprazole (0.5 mg/kg) may provide protection, evidence remains less consistent, and further research is needed before definitive recommendations can be made¹. 

Why Prevention May Be More Practical Than Treatment 

The concept of Number Needed to Treat (NNT) helps clinicians understand the practical value of preventive therapy. The meta-analysis reported an overall NNT of 1.8, meaning that treating fewer than two horses with prophylactic omeprazole prevents one additional case of squamous gastric ulceration¹. 

For horses with a previous history of ulcers, the NNT was even lower at 1.5, indicating an especially strong preventive benefit. 

Put differently, prophylactic omeprazole was associated with approximately 556 fewer cases of squamous gastric ulceration per 1,000 horses treated¹. 

Considerations for Long-Term Use 

Current recommendations from the European College of Equine Internal Medicine support the use of omeprazole for ulcer prevention in horses exposed to ulcer-inducing conditions. However, specific guidelines regarding ideal dosage and duration remain limited². 

While available studies report a low incidence of adverse effects, the long-term consequences of prolonged proton pump inhibitor use in horses have not yet been fully evaluated. Future research is needed to determine optimal dosing schedules, treatment duration, and potential alternatives such as H₂ receptor antagonists or mucosal protectants. 

Conclusion 

Evidence strongly supports the use of prophylactic omeprazole in reducing the incidence of squamous gastric ulcers in horses undergoing training. Horses with a previous history of ulceration appear to derive even greater benefit, with substantial reductions in recurrence risk. As research continues to refine dosage recommendations, omeprazole remains one of the most effective pharmacological tools available for protecting equine gastric health in high-risk management and training environments. 

References 

1. Mason LV, Burden FA, Carslake HB, et al. Omeprazole compared with sham for prevention of gastric ulceration in horses: A systematic review and meta-analysis. Equine Veterinary Journal. 2019;51(1):11–19. 
2. European College of Equine Internal Medicine (ECEIM). Consensus Statement on Equine Gastric Ulcer Syndrome, cited in Mason et al., 2019.