Treating Equine Stomach Ulcers with Omeprazole

December 9, 2021 (published)

A large number of performance horses suffer from gastric or stomach ulcers. A recent study reveals a method to make treatment more successful and potentially less expensive. There are 2 different areas in the horse’s stomach. One is the squamous area, and the other is the glandular area This is important because the location of the ulcer helps the veterinarian determine a likely cause and chance of healing. Ulcers in the glandular portion of the stomach are much more difficult to heal than those in the squamous portion. The drug omeprazole is commonly used to treat gastric ulcers. Although effective in most cases, the drug is expensive and is used for 30 days.

To determine the absorption characteristics of omeprazole, Dr. Ben Sykes from the University of Liverpool performed a study on feeding time and absorption of the drug. He found that compared to giving the drug to fasted horses, feeding hay with the drug decreased absorption up to 66%. This decreased absorption correlated with decreased acid suppression up to 40% of the 24 hour period. If omeprazole is given when the horse has hay available, the horse is not protected from acid for 40% of the day. Also, three out of the six horses tested had little acid suppression at all over a five day period. So, this expensive drug was wasted and could be the reason some horses seemingly do not respond to treatment. Although it is not good to fast horses with stomach ulcers, this report indicates that feeding at 6:00 pm would be okay as long as the horse has consumed all the feed by 10:00 pm and then give the omeprazole at 7:00 am, feeding the horse one hour later for optimal absorption. With higher absorption, it is possible that the dosage could be decreased making the drug less expensive to use for treatment.    

VIN News Service commentaries are opinion pieces presenting insights, personal experiences and/or perspectives on topical issues by members of the veterinary community. To submit a commentary for consideration, email

Information and opinions expressed in letters to the editor are those of the author and are independent of the VIN News Service. Letters may be edited for style. We do not verify their content for accuracy.