Keeping Up from the 2016 AAEP Convention: Effect of Dose and Diet on Omeprazole

Editor’s note: Each year, the American Association of Equine Practitioners (AAEP) Convention brings forward cutting-edge scientific topics. This venue provides excellent continuing education for equine practitioners from around the world, giving insights into state-of-the-art medical, surgical and business strategies. At the 2016 Convention in Orlando, Florida, interesting papers were presented at the Kester News Hour. Many of the papers discussed have practical implications for common problems in equine medicine and surgery. In addition, this information can help provide practitioners with material to educate clients in the best health care for their horses. We will cover four of these topics in separate articles on

Credit: Thinkstock There is a difference when horses are dosed with omeprazole on an empty versus a full stomach, with better results realized when hay is withheld for two hours before and after giving omeprazole.

Effects of Dose and Diet on Omeprazole

Another feeding topic focused on the effects of diet and dose on the duration and potency of acid suppression from administration of omeprazole used for treatment and prevention of gastric ulcer syndrome (GUS). The horses in the study (Sykes, B.W.; Underwood, C.; Greer, R.; McGowan, C.M.; Mills, P.C. The effects of dose and diet on the pharmacodynamics of omeprazole in the horse. Equine Vet J. 2016 Aug 24) were fed two different diets comparing ad lib hay versus a racehorse diet containing low fiber and high concentrates fed twice a day. The researchers measured the pH of two sites in the stomach, with the goal that the pH remains above 4 for 60% of the day. 

The results are somewhat sobering considering many horses receive omeprazole for control of GUS: The best method of accomplishing this higher pH level was achieved by administering the 4 mg/kg (treatment) dose of omeprazole and only in horses fed a high concentrate diet. The result in horses fed ad lib hay was considered poor, as were the results from the 1 mg/kg (preventive) omeprazole dose. 

The study concluded that feeding ad lib hay is not a bad idea, especially since this is one method of controlling the development of gastric ulcer disease. However, there is a difference when horses are dosed on an empty versus a full stomach, with better results realized when hay is withheld for two hours before and after giving omeprazole, i.e., best results are achieved on an empty stomach.

The Take Home

Common medical conditions seen by equine practitioners continue to be researched for better approaches and solutions. Having this knowledge in hand enables veterinarians to keep abreast of cutting-edge advances. Clients benefitting from this information will be better served, hopefully with improved outcomes for their equine partners. Client satisfaction from favorable outcomes is not only gratifying to the practitioner but it also inspires loyalty to your practice.

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