GastroGard and UlcerGard are FDA-approved omeprazole formulations specifically designed for horses. GastroGard is the prescription-strength treatment dose for equine gastric ulcer syndrome (EGUS), while UlcerGard is the lower-dose over-the-counter formulation approved for ulcer prevention. Both are manufactured by Boehringer Ingelheim and are among the most commonly used medications in equine practice, particularly for performance horses. Omeprazole is a proton pump inhibitor (PPI) that reduces stomach acid production, allowing ulcers to heal and preventing new ones from forming.
What Is Equine Gastric Ulcer Syndrome (EGUS)?
Gastric ulcers are remarkably common in horses. Studies consistently show that:
- Up to 90% of racehorses have gastric ulcers
- 60-70% of performance and sport horses are affected
- 50-60% of show horses have some degree of gastric ulceration
- Even pleasure horses and broodmares can be affected, though at lower rates
EGUS encompasses two distinct conditions:
- Equine Squamous Gastric Disease (ESGD): Ulceration of the upper, non-glandular portion of the stomach. This is the more common and better-understood form. It responds well to omeprazole.
- Equine Glandular Gastric Disease (EGGD): Ulceration of the lower, glandular portion of the stomach. This form is less well understood and may require different or additional treatment approaches. Omeprazole alone may be less effective for EGGD.
Risk Factors for Gastric Ulcers in Horses
- Intense exercise and training (increases abdominal pressure, splashes acid onto unprotected squamous mucosa)
- Intermittent feeding (horses are designed to eat small amounts continuously; long fasting periods allow acid to accumulate)
- High-grain, low-forage diets
- Stress from competition, travel, stall confinement, or social changes
- NSAID use (phenylbutazone, flunixin meglumine)
Signs of Gastric Ulcers
- Poor appetite or picky eating
- Weight loss or poor body condition
- Decreased performance
- Behavioral changes (girthiness, reluctance to work, irritability)
- Mild recurring colic, especially after eating
- Poor coat quality
- Changes in attitude or temperament
Many of these signs are subtle and nonspecific. Definitive diagnosis requires gastroscopy (endoscopic examination of the stomach), which is performed by a veterinarian.
How Does Omeprazole Work?
Omeprazole is a proton pump inhibitor that irreversibly binds to the hydrogen-potassium ATPase enzyme system (the proton pump) in the parietal cells of the stomach lining. This blocks the final step of acid secretion, reducing gastric acid production by up to 99%. By dramatically lowering stomach acidity, omeprazole creates an environment that allows existing ulcers to heal and prevents new ulcers from forming.
Key pharmacological points for horses:
- Omeprazole must be formulated specifically for horses. The equine stomach environment differs from humans, and human omeprazole capsules are not reliably bioavailable in horses. GastroGard and UlcerGard use a buffered formulation designed for equine gastric conditions.
- Peak acid suppression occurs within 3-5 days of starting treatment.
- Effects are reversible once the medication is stopped, though new parietal cells must be generated to restore full acid production.
Dosage
Your veterinarian will determine the appropriate dose and duration based on gastroscopy findings and clinical assessment.
| Indication | Product | Dose | Frequency | Duration |
|---|---|---|---|---|
| Treatment of gastric ulcers | GastroGard (Rx) | 4 mg/kg (1 syringe per 1250 lb horse) | Once daily, on empty stomach | 28 days (minimum); reassess with gastroscopy |
| Prevention of gastric ulcers | UlcerGard (OTC) | 1 mg/kg (1/4 syringe per 1250 lb horse) | Once daily | During periods of increased risk |
- Treatment dose: 4 mg/kg once daily for a minimum of 28 days. Many horses require 4-8 weeks of treatment for complete ulcer healing. Your veterinarian may recommend follow-up gastroscopy to confirm healing before discontinuing treatment.
- Prevention dose: 1 mg/kg once daily during periods of increased stress such as competition, travel, or training intensification.
- Tapering: After a treatment course, many veterinarians recommend gradually reducing the dose over 1-2 weeks rather than stopping abruptly. Abrupt discontinuation after prolonged use may lead to rebound acid hypersecretion.
Administration Tips
- Give on an empty stomach, ideally first thing in the morning before the horse is fed.
- Wait at least 30-60 minutes before feeding after administering omeprazole.
- Administer the oral paste directly into the mouth using the syringe.
GastroGard vs. UlcerGard
| Feature | GastroGard | UlcerGard |
|---|---|---|
| Indication | Treatment of gastric ulcers | Prevention of gastric ulcers |
| Dose | 4 mg/kg (full syringe for 1250 lb horse) | 1 mg/kg (quarter syringe for 1250 lb horse) |
| Prescription required | Yes | No (OTC) |
| Approximate cost per day | $30-40/day (treatment dose) | $8-12/day (prevention dose) |
| Duration | 28+ days | During risk periods |
| Formulation | Identical omeprazole paste | Identical omeprazole paste |
The paste formulation is identical in both products. The key difference is the labeled indication and dosing. Some horse owners use multiple UlcerGard syringes at the treatment dose as a cost-saving strategy, though this should be discussed with a veterinarian.
Side Effects
Omeprazole is generally well tolerated in horses with few reported side effects.
| Common Side Effects | Potential Concerns with Long-Term Use |
|---|---|
| Typically none at standard doses | Possible changes in hindgut microbial populations |
| Occasional loose stool | Theoretical risk of mineral absorption changes |
| Rebound acid hypersecretion after abrupt discontinuation | |
| Potential interaction with calcium absorption |
Long-term continuous use of omeprazole (beyond 8-12 weeks) has raised some theoretical concerns:
- Hindgut health: By altering gastric pH, omeprazole may change the microbial populations passing into the hindgut. The clinical significance of this in horses is still being studied.
- Calcium absorption: Prolonged acid suppression may affect calcium metabolism, though clinically significant effects have not been established in horses.
- Rebound acid production: Stopping omeprazole abruptly after prolonged use may lead to temporarily increased acid production. Gradual tapering is recommended.
Drug Interactions
- Sucralfate: If used concurrently, give omeprazole and sucralfate at different times (at least 2 hours apart). Sucralfate requires an acidic environment to be effective.
- NSAIDs (phenylbutazone, flunixin): Omeprazole is often used alongside NSAIDs to help protect the squamous gastric mucosa, though it does not prevent NSAID-induced right dorsal colitis.
- Other acid suppressants (ranitidine, famotidine): Generally not combined with omeprazole as they target the same outcome through different mechanisms.
Cost Considerations
Cost is a significant concern for many horse owners, as a full treatment course of GastroGard can be expensive.
| Product | Approximate Cost | Monthly Cost at Treatment Dose |
|---|---|---|
| GastroGard (brand, Rx) | $35-42 per syringe | $980-1,260/month |
| UlcerGard (brand, OTC) | $35-42 per syringe | $250-315/month (prevention dose) |
| Compounded omeprazole (various) | $5-15 per daily dose | $150-450/month |
| Generic omeprazole paste (equine) | $10-25 per syringe | $280-700/month |
A Note on Compounded Omeprazole
Compounded omeprazole products are significantly less expensive than GastroGard and are widely used. However, studies have shown that some compounded omeprazole formulations have inconsistent bioavailability and may not achieve the same level of acid suppression as the FDA-approved products. The buffering system in GastroGard/UlcerGard protects omeprazole from degradation in the acidic equine stomach. If you are considering a compounded product, discuss this with your veterinarian and look for compounding pharmacies that have tested their formulations for equine bioavailability.
Frequently Asked Questions
Does my horse definitely have ulcers? The signs of gastric ulcers in horses overlap with many other conditions. The only way to definitively diagnose gastric ulcers is through gastroscopy (stomach endoscopy). While empirical treatment with omeprazole is common, a definitive diagnosis allows your veterinarian to determine the severity, location, and type of ulceration, which affects treatment decisions. Consult your veterinarian about whether gastroscopy is recommended.
Can I use human omeprazole capsules for my horse? Human omeprazole capsules (such as Prilosec) are enteric-coated and designed for the human GI tract. Studies have shown that these capsules do not reliably dissolve and become bioavailable in the equine stomach. GastroGard/UlcerGard and properly formulated equine omeprazole products are recommended for effective treatment.
How do I prevent ulcers without medication? Management strategies that help reduce ulcer risk include:
- Providing continuous or frequent access to forage (hay or pasture)
- Feeding hay before grain or concentrate meals
- Reducing grain and increasing forage in the diet
- Minimizing stall confinement and providing social interaction
- Managing stress from competition and travel
- Avoiding prolonged fasting (no more than 4-6 hours without forage)
My horse finished the treatment course. Will the ulcers come back? Recurrence is common if the underlying risk factors are not addressed. Performance horses in active training and competition are at ongoing risk. Your veterinarian may recommend periodic prevention dosing (UlcerGard) during high-risk periods along with management changes to reduce recurrence.