EGUS: Does Anything Other Than Omeprazole Make a Difference?

Squamous ulceration reflects primary acid injury, whereas glandular disease is an erosive gastritis of unknown aetiology, acid–mucosal contact is a component but not the sole cause (Murray et al. 1997; Hepburn 2012). The 3 aims of gastric ulcer healing are neutralise acid, promote mucosal repair, and improve management practices.

Squamous ulceration
Whilst spontaneous healing can occur in resting horses, pharmacologic therapy is typically required, and can be effective regardless of training intensity. The accepted approach is high quality acid suppression using a proton pump inhibitor. Currently a pH buffered omeprazole paste (GastroGard, Merial) is the only UK equine licensed product. Dependent upon population and study design, 4 mg/kg bwt per os q. 24 h for 28 days results in healing in up to 87% and improvement in up to 99% of horses in full work. (Murray 1995; Murray et al. 1997). Concurrent significant improvement in performance, attitude, appetite, appearance and weight gain occur (MacAllister and Sangiah 1993). Ideally it should be administered 30 min before feeding to increase bioavailability. In this author’s experience, treatment duration can be estimated from ulcer appearance: widespread superficial erosion resolves more rapidly than deeper focal ulceration. A reduced dose (1–2 mg/kg bwt per os q. 24 h) or shortened duration (14–21 days) can be used in horses working at lower intensities, with comparable success (Andrews et al.1999). Omeprazole is acid labile and the equine bioavailability of human preparations (given to man on an empty, hence neutral stomach) is extremely low, leading to minimal acid suppression and no ulcer healing. Compounded equine alternatives typically do not have the vehicle pH or persistence of GastroGard and rarely show any significant change in gastric pH (Merritt et al. 2003). [...]