Ulcer Medications: What Nobody Tells You and What You Need To Know

The most commonly used equine ulcer medications on the market generally come under names containing Gastro/Ulcer/Guard and contain the active ingredient omeprazole, which belongs to the class of drugs known as Proton Pump Inhibitors (PPIs)[i] [ii]. These drugs work by reducing (normal, healthy) gastric acid production by blocking the enzymes located in the parietal cells of the stomach wall, which are responsible for producing these essential digestive acids[iii].

Pepsin, hydrochloric acid and other digestive enzymes are normal, healthy products of the equine digestive system and are essential for the proper digestion of food, as a line of defence against some pathogens, and maintaining healthy bacterial flora of the gastrointestinal tract (GIT).

By using omeprazole, normal digestion is inhibited. The digestion of protein and fats occurs primarily through the action of pepsin and hydrochloric acid, both of which are unable to be produced through the use of PPIs. Hydrochloric acid and pepsin are also essential to prevent excessive bacterial fermentation of soluble sugars in the stomach[iv]. By blocking the production of these digestive acids, gastric nitrate rendering bacteria levels increase, as do carcinogenic nitrosamines in gastric juice. Without adequate digestive enzyme production, there is an increased risk of intestinal bacterial overgrowth and excessive gas production, which further inhibits digestion and can increase the risk of colic[v].

Intestinal bacterial overgrowth is also associated with poor immune function, increased inflammation and increased risk of viral infections[vi] [vii]. Stop for a minute and consider what this means for you as a trainer, owner or rider. For a racehorse this can mean increased risk of respiratory infection and increased susceptibility and slower healing from injury. This translates to more down time for the horse and likely lost revenue. For a stud manager, think of a foal who is stabled due to compromised health, is on multiple treatments and is given omeprazole as a precautionary measure. The foal’s ability to be nourished by it’s mother’s milk and therefore grow and thrive has been impeded; it’s ability to further fight infection has been reduced; and its risk of developing diarrhoea has increased. For a horse with an inflammatory condition such as osteoarthritis owners are constantly doing all they can to reduce inflammation. Therefore, consider the increased likelihood of lameness and joint destruction associated with elevated inflammatory mediators, as a by product of using PPIs.

Omeprazole is commonly co-prescribed with the use of non-steroidal anti-inflammatories (NSAIDs) such as phenylbutazone (bute) and flunixin meglumine (Banamine). Most people are well aware that the use of NSAIDs commonly induces gastro-duodenal injury and can be a causative factor of GIT bleeding and ulcers. Many horse people take a proactive approach and thus use omeprazole as a believed preventative measure to avoid these side effects. Animal research has clearly demonstrated that PPIs do not prevent the development of these undesirable side effects, instead actually exacerbating NSAID-induced intestinal damage[viii].

Human studies have also shown that the use of omeprazole may increase the risk of bone fractures[ix] [x]. Again, think of this in practical terms: Many trainers treat their racehorses daily with some form of ulcer medication, believing that they are taking a proactive approach. Now consider the increased risk of fracture.

PPIs also decrease intra-gastric vitamin C levels and may increase serum cortisol levels[xi]. Consistently elevated cortisol levels can lead to reduced performance, poor immune function and delayed recovery. Vitamin C is absolutely essential for a multitude of functions including: immune health; healing; collagen production; bone health and growth; nutrient absorption; healthy hoof growth; iron absorption; sperm motility; and regulating cortisol levels. Therefore, regardless of the discipline your horse is involved in, and its life stage, this is an important factor.

Evidence suggests that long-term use of omeprazole is associated with vitamin B12, iron, magnesium and calcium deficiencies, through altered metabolism and absorption[xii]. Amongst other things, these are nutrients essential for energy production; musculoskeletal health; red blood cell production; immune function; growth and performance[xiii].

The effects of fatigue are an important concern for horses competing across all disciplines. Omeprazole may be a significant cause of fatigue, not only through altered nutrient status as outlined above, but also through direct effect on proton pumps throughout the body. Proton pumps are present in just about every cell in the body, and whilst omeprazole is designed to interact with proton pumps in the stomach, research suggests that its actions are non-specific: it can effect all proton pumps in the body[xiv]. Given this, PPIs have the ability to hamper mitochondrial function, leading to a reliance on anaerobic systems for energy production, leading to rapid fatigue[xv].

So what can you do to optimise your horse’s GIT health?

Naturopathically, there are many beneficial herbal, nutritional and management strategies that can be employed to help both prevent and treat ulcers, in addition to achieving optimal GIT health. Therapeutics prescribed and treatment aims differ between cases and depend upon the individual horse and the circumstances. When the most appropriate treatments are professionally selected and prescribed, they will benefit the horse’s overall health, yielding favourable results without the negative side effects of omeprazole.


It is extremely important to consider the following questions in relation to the use of any treatment for your horse:

  • What is this treatment specifically for?
  • What treatment aims will this drug/supplement/additive support?
  • What is necessitating this treatment? Are there practical management or dietary steps that can be employed to reduce the perceived need for this treatment?
  • What are the potential risks associated with this treatment?
  • What are the potential benefits associated with this treatment?
  • What alternatives are available to this treatment? Are they safer? More effective? More relevant?
  • Am I prescribing this treatment ‘just because’ or ‘just in case’?

If you cannot confidently answer all of the above questions, then seek the professional advice of those that can. We all want what is best for our horses, and it is sad (and expensive) when we are employing methods that may not only be ineffective for our horse’s ‘problem’ at hand, but cause further negative health implications.


[i] Merial 2014, GastroGard (omeprazole) inhibits acid production at the source, viewed 14th March 2017, www.ulcergard.com

[ii] Thomson, A et al. 2010, Safety of the long-term use of proton pump inhibitors, World Journal of Gastroenterology, vol.16, no.19, pp.2323-30.

[iii] Marks, J 2017, Proton Pump Inhibitors (PPIs), viewed 14th March 2017,  www.medicinenet.com

[iv] Cubbit, T 2010, The horse’s digestive system, Hygain, viewed 31st March 2017, hygain.com.au

[v] Fujimori, S 2015, What are the effects of proton pump inhibitors on the small intestine?, World J Gastroenterol. v.21, no.22, pp.6817-9.

[vi]Wilhelm, S et al 2013, Perils and Pitfalls of Long-term Effects of Proton Pump Inhibitors, Expert Rev Clin Pharmacol,vol.6, no.4 pp.443-451. 

[vii] Dukowicz, A et al 2007, Small Intestinal Bacterial Overgrowth: A Comprehensive Review, Gastroenterology and Hepatology, vol.3, no.2, pp.112-22.

[viii] Wallace, J et al. 2011,Proton pump inhibitors exacerbate NSAID-induced small intestinal injury by inducing dysbiosis, Gastroenterology, vol. 141, no.14, pp.1314-22.

[ix] FDA 2016, Possible Increased Risk of Bone Fractures With Certain Antacid Drugs, U.S. Food & Drug Administration, viewed 14th March 2017, www.fda.gov

[x]Wilhelm, S et al 2013, Perils and Pitfalls of Long-term Effects of Proton Pump Inhibitors, Expert Rev Clin Pharmacol,vol.6, no.4 pp.443-451. 

[xi] Heidelbaugh, J 2013,Proton pump inhibitors and risk of vitamin and mineral deficiency: evidence and clinical implications, Ther Adv Drug Saf, vol.4, no.3, pp.125–33.

[xii] Heidelbaugh, J 2013,Proton pump inhibitors and risk of vitamin and mineral deficiency: evidence and clinical implications, Ther Adv Drug Saf, vol.4, no.3, pp.125–33.

[xiii] UHN Daily 2016, Don’t Ignore The Health Hazards of Proton Pump Inhibitors, viewed 3rd April 2017, universityhealthnews.com

[xiv] Mattsson, J et al 1991,Omeprazole and bafilomycin, two proton pump inhibitors: differentiation of their effects on gastric, kidney and bone H(+)-translocating ATPases, Biochem Biophys Acta, vol. 1065, no.2, pp.261-8.

[xv] Kresser, C 2016, The Dangers of Proton Pump Inhibitors, viewed 4th April 2017, www.chriskresser.com

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