Omeprazole is a proton pump inhibitor (PPI) and the primary drug used for the treatment and prevention of Equine Gastric Ulcer Syndrome (EGUS). GastroGard is the FDA-approved treatment formulation, and UlcerGard is the FDA-approved prevention formulation. Both are oral paste products specifically designed for horses with a buffered, enteric-protected delivery system to ensure adequate bioavailability in the equine stomach.
Overview
EGUS is extremely common in horses, with prevalence rates of 60-90% in performance horses and up to 50% in foals. The equine stomach continuously produces hydrochloric acid, and horses that undergo stress, exercise, fasting, or NSAID therapy are at high risk for gastric ulceration. Omeprazole works by irreversibly inhibiting the hydrogen-potassium ATPase pump (proton pump) on gastric parietal cells, reducing gastric acid secretion by up to 99%. It is highly effective for squamous gastric ulceration and is also used for glandular disease, though glandular ulcers may respond less predictably.
Uses
- Treatment of squamous gastric ulcers — FDA-approved indication (GastroGard)
- Prevention of gastric ulcer recurrence — FDA-approved indication (UlcerGard)
- Glandular gastric ulceration — often used in combination with sucralfate
- Gastric ulcer prophylaxis during NSAID therapy — commonly co-prescribed with phenylbutazone or flunixin
- Ulcer prevention during stressful events — transport, competition, stall rest
- Foal ulcer management — under veterinary guidance
Dosage
Consult your veterinarian for proper diagnosis and dosing.
| Indication | Dose | Route | Frequency | Duration |
|---|---|---|---|---|
| Treatment (GastroGard) | 4 mg/kg | Oral paste | Once daily | 28 days (minimum) |
| Prevention (UlcerGard) | 1 mg/kg | Oral paste | Once daily | As needed |
| Foals (treatment) | 4 mg/kg | Oral | Once daily | As directed by vet |
Administer on an empty stomach, ideally 30-60 minutes before feeding, for optimal absorption. Treatment courses typically run a minimum of 28 days. Gastroscopy is recommended to confirm ulcer healing before discontinuing.
Tapering: Abrupt discontinuation after treatment may cause acid rebound and ulcer recurrence. Many veterinarians recommend a gradual taper over 1-2 weeks, stepping down from treatment to prevention dose.
Compounded products: The FDA-approved paste formulation (GastroGard/UlcerGard) uses a proprietary buffered delivery system. Studies have shown that many compounded and generic omeprazole products have significantly lower bioavailability, potentially resulting in treatment failure. Discuss product selection with your veterinarian.
Side Effects
Omeprazole is generally well tolerated in horses. Reported side effects are uncommon:
| Common | Rare/Potential Concerns |
|---|---|
| Mild transient diarrhea | Altered gut microbiome with prolonged use |
| Rare appetite changes | Theoretical calcium/mineral absorption effects with very long-term use |
| Acid rebound upon abrupt discontinuation |
Long-term safety data in horses is reassuring, but extended use beyond several months should be guided by veterinary evaluation to determine if ongoing therapy is warranted.
Drug Interactions
- Sucralfate: Often combined for glandular ulcers. Administer omeprazole at least 30 minutes before sucralfate, as sucralfate requires an acidic environment for activation.
- Phenylbutazone / flunixin / other NSAIDs: Omeprazole helps protect against squamous ulceration but does not prevent right dorsal colitis.
- Clopidogrel: Theoretical interaction (documented in humans; clinical significance in horses unknown).
- Other acid-reducing drugs (ranitidine, famotidine): Generally not combined, as omeprazole is more effective.
Contraindications
- Known hypersensitivity to omeprazole or other PPIs
- Omeprazole should not be used as a substitute for veterinary diagnosis; gastric ulcers should be confirmed by gastroscopy when possible
- Use with caution in horses with liver disease
Storage
- Store at 68-77 degrees F (20-25 degrees C).
- Do not refrigerate or freeze the paste formulation.
- Protect from moisture.
- Use within the expiration date; degraded product may have reduced efficacy.
Frequently Asked Questions
How do I know if my horse has ulcers? Common signs include poor appetite, weight loss, poor body condition, girthiness, behavioral changes, mild recurrent colic, and poor performance. However, many horses with ulcers show subtle or no outward signs. Gastroscopy is the gold standard for diagnosis.
Is UlcerGard the same as GastroGard? Both contain omeprazole in the same FDA-approved paste formulation. GastroGard is labeled at the treatment dose (4 mg/kg), while UlcerGard is labeled at the prevention dose (1 mg/kg). UlcerGard is available over the counter.
Can I use a compounded omeprazole to save money? While compounded products are less expensive, studies have repeatedly shown that many compounded omeprazole preparations have significantly lower bioavailability than the FDA-approved paste. This may lead to inadequate acid suppression and treatment failure. Discuss cost-effective options with your veterinarian.
Does omeprazole protect against NSAID-induced right dorsal colitis? No. Omeprazole protects against gastric (stomach) ulceration only. It does not protect the colon. The best way to reduce right dorsal colitis risk is to use the lowest effective NSAID dose for the shortest duration.
This information is for educational purposes only and does not replace professional veterinary advice. Always consult your veterinarian before administering any medication to your horse.