FDA-approved GastroGard (Omeprazole) Paste is used for treatment and prevention of recurrence of gastric ulcers in horses. GastroGard Paste is recommended for oral use in horses and foals 4 weeks of age and older. Each GastroGard syringe contains 2.28 grams omeprazole. For treatment, administer GastroGard once daily for 4 weeks, at the rate of one tube per 1250 lbs. of body weight. For prevention of recurrence, continue with 1/2 tube daily per 1250 lbs. for an additional 4 weeks. Omeprazole.