by Audrey Burkard
Omeprazole? – I heard it in conjunction with treatment for gastric ulcers in horses. I started searching on the internet and what I found made me curious.
Omeprazole was first used in humans because of its acid-minimizing function in the stomach environment. Diseases like the Peptic Ulcer Disease (PUD), the Gastroesophageal Reflux Disease (GERD) (mucosal damage at the esophagus) or the Zollinger-Ellison Syndrome (production of the hormone gastrin which causes excess-production of HCL) are treated with this component. (Wikipedia 2007)
The interesting thing is that nausea (vomiting) and abdominal pain are among the most common adverse effects of the usage of omeprazole in humans. (Wikipedia 2007) BUT abdominal pain (caused by gas) in horses leads to colic and as far as I know a horse which vomits will be dead in a foreseeable period of time! So what does omeprazole do in the horses’ body and what are its side effects?
Omeprazole is one of the proton pump inhibitors used for the treatment of Equine Gastric Ulcer Syndrome (EGUS). Lesions (ulcers) develop when there is an imbalance in the stomach environment of protective and inciting factors of the stomach mucosa. (Murray et al. 1989, Nappert et al. 1989) Acid does play an important role as it is the main factor damaging the stomach walls. (Murray et al. 1989, Nappert et al. 1989, Mertz 1991) (For further information about the syndrome in horses see issue 1/2007- Equine Gastric Ulcer Syndrome). This is why the treatments of the common syndrome mainly try to increase the pH of the stomach environment which drops because of the increased acid content.
Antacids for instance are neutralizing the acid in the stomach, bismuth compounds are having little neutralizing capacity and do protect the gastric cells, prostaglandin is inhibiting the secretion of acid and therefore increases the pH of the stomach but also stimulates the secretion of mucus and bicarbonate and provides cytoprotection for the gastric mucosa. These agents could – regarding their function – all be useful in healing of ulcers but at the moment there is insufficient data about these agents and their effects on gastric ulcers in horses although they can be found as ingredients in products for the treatment of EGUS. (Picavet 2002, Marqués 2007)
H2 receptor antagonists (like cimetidine, ranitidine, nizatidine and famotidine) are having also an inhibiting function on the secretion of acid. Especially, ranitidine is used in the treatment of horses. It is proven to be effective in the treatment of ulcers in the studies of Murray et al. (1996), Murray and Grodinsky (1992) and Sanchez et al. (1998). In another article from Picavet (2002), however, is stated that scientific evidence for the enhancement of ulcer healing in horses regarding these agents is lacking. The reason for these differences in recording the efficiency of these receptors could be that their degree and duration of acid suppression varies among horses. (Bech et al. 1986, Furr et al. 1989)
Sucralfate, which are aluminium hydroxide and sucrose octasulfate, forming a sort of gel at a stomach pH lower than 4. (Picavet 2002) This gel is binding to the stomach walls and enhances mucus bicarbonate, local prostaglandin production and local blood flow (all protective factors). Moreover, it binds and concentrates epidermal growth factor (protective factor) and inhibits pepsin (inciting factor). (McCarthy 1991) Nevertheless, it is not proven to heal gastric ulcers but it can additionally be used in treatments with ranitidine. (Murray 2003)
By contrast, proton pump inhibitors seem to be a miracle cure. In the parietal cells where stomach acid is produced, hydrogen ion pumps are playing an important role in gastric acid production as they secret the hydrogen to form hydrochlorid acid (HCL). (Marqués 2007) This pump is an enzyme called the hydrogen (H+)- potassium(K+) adenosine triphosphatase. Inhibitors for this pump are lansoprazole and omeprazole. The latter, is a commonly used treatment for gastric ulcers as it has shown in a lot of studies to be effective regarding the healing of gastric ulcers and the prevention of their reoccurrence. It is applied orally and takes about 3-5 days till it starts to act on the secretion of acid. (Picavet 2002) It is moreover easy to use as it only needs to be given every 24 hours to the horse whereas others like sucralfate and histamine type 2 receptor antagonists need to be given every 6 – 8 hours. Moreover, these agents need to be given at a higher dose (Histamine 2 receptor antagonists: 6.6 mg/kg; sucralfate: 20 mg/kg) than omeprazole (4mg/kg). (Murray 2003)
It should be taken in to consideration, when using omeprazole that compound forms of this agent seem to be ineffective as it is in this form inactivated. (Andrews 2005)
Omeprazole can be used for treatment (4 mg/kg of body weight), for prevention of reoccurrence (2 mg/kg of body weight) and prevention of ulcers (1 mg/kg of body weight) (Andrews 2005; Andrews et al. 1999) and that without any side effects occurring.
Nevertheless, having the thought in mind that there is a product on the market accessible and proved to be effective regarding the healing and the prevention of EGUS it should not let those who are concerned forget, that the original causes of the disease must be treated!
Andrews FM (2005), “Ulcers in the Stomach and Colon; Diagnosis and Treatment: A Pain in the Gut!” American Association of Equine Practitioners – AAEP –
Focus Meeting, 2005 – Québec, QC, Canada; available from www.ivis.org
Andrew FM, Bernard WV, Byars TD (1999), “Recommendations for the diagnosis and treatment of equine gastric ulcer syndrome (EGUS)”, Equine Vet. Educ.;
1: pp. 122-134
Bech JL, Byars TD (1986) “Gastroduodenal ulceration in foals”, Equine Vet J; 18(4): pp. 307-312.
Furr MO, Murray MJ (1989), “Treatment of gastric ulcers in horses with histamine
type 2 receptor antagonists”, Equine Vet J Suppl; 7: pp. 77-79.
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McCarthy DM (1991) “Sucralfate”, N Engl J Med; 325: pp. 1017-1025.
Mertz HR, Walsh JH (1991), “Peptic ulcer pathophysiology”, Med Clin North Am; 75: pp. 799-814.
Murray MJ (1997), “Gastroduodendal ulceration”, In: “Current therapy in Equine Medicine”, 4th ed., Ed: N.E. Robinson: pp. 191-197
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Congress on Equine Medicine and Surgery 2003, P. Chuit, A. Kuffer and S. Montavon (Eds.) Publisher: International Veterinary Information Service (www.ivis.org), Ithaca, New York, USA. [online] (cited May 5th, 2007) Available from: www.ivis.org
Nappert G, Vrins A, Larybyere M (1989), “Gastroduodenal ulceration in foals”, Compend Cont Educ Pract Vet; 11: pp. 345.
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Belgium. [online] (cited May 8th, 2007) Available from: http://www.ivis.org
Sanchez LC, Lester GD, Merritt AM (1998), “Effect of ranitidine on intragastric pH in clinically normal neonatal foals”, J Am Vet Med Assoc.; 212: pp. 1407-1412
Wikipedia (2007) “Omeprazole” [online]. Available from: http://en.wikipedia.org/wiki/Omeprazole [accessed 25 May 2007]