A comparison of three doses of omeprazole in the treatment of equine gastric ulcer syndrome: A blinded, randomised, dose-response clinical trial

Reasons for performing the studyA previous study demonstrated that a dose effect between 1.6 and 4.0mg/kg bwt of omeprazole per os s.i.d. is present in the treatment of equine gastric ulceration. In the same study, healing of glandular ulceration appeared inferior to healing of squamous ulceration. However, several limitations were recognised in that study and further investigation is warranted. ObjectivesTo further investigate the presence of a dose relationship in the treatment of gastric ulceration under conditions that may favour omeprazole efficacy such as administration prior to exercise and after a brief fast, and potential differences between the response of squamous and glandular ulceration to omeprazole therapy. Study designA blinded, randomised, dose-response clinical trial. MethodsSixty Thoroughbred racehorses with grade 2/4 squamous and/or glandular ulceration were identified by gastroscopy. Horses were randomly assigned to receive either 1.0, 2.0 or 4.0mg/kg bwt of enteric coated omeprazole per os s.i.d. 1-4h prior to exercise. Gastroscopy was repeated at approximately 28 days. ResultsThe lower doses studied (1.0 and 2.0mg/kg bwt) were noninferior to the reference dose (4.0mg/kg bwt) in the treatment of squamous ulceration. Healing was greater in squamous ulceration than glandular ulceration (86% vs. 14%; P<0.0001). Improvement in ulcer grade was more likely in squamous lesions than glandular lesions (96% vs. 34%; P<0.0001). Worsening of the glandular ulcer grade was observed in 36% of horses. ConclusionsThe results of this study suggest that, under the conditions studied, where omeprazole is administered before exercise and following a brief fast, doses of omeprazole as low as 1mg/kg bwt per os s.i.d. may be as effective as higher doses. The proportion of glandular ulceration that heals with 28 days of omeprazole therapy is less than that of squamous ulceration.