Misoprostol is a drug used in horses to prevent ulcers from developing in the hindgut and stomach. It is commonly prescribed to horses that require regular use of non-steroidal anti-inflammatory drugs (NSAIDS), which can cause ulcers to form.

Misoprostol is also used to treat gastric ulcers in the stomach’s glandular region in horses that are not responding to conventional treatments, such as omeprazole or sucralfate.

This medication contains a synthetic (man-made) form of prostaglandin E1 (PGE1), a hormone naturally produced by horses and found in high amounts in the digestive tract. [1]

Prostaglandins protect the digestive tract from damage and support the healing of the intestinal barrier once ulcers have formed. If your horse is on long-term NSAID therapy for pain management, discuss misoprostol with your vet.

There are also other ways you can naturally reduce the risk of ulcers in your horse. These strategies should be used at the same time as administering Misoprostol.

Misoprostol for Horses

Misoprostol (Cytotec®) is an FDA-approved drug used in humans to prevent or treat gastric ulcers caused by NSAIDs. [2]

In horses, it is used off-label to prevent NSAID-induced hindgut issues such as colitis or hindgut ulcers. In addition, it can be used to treat gastric ulcers in the stomach’s glandular region.

Misoprostol is synthetic prostaglandin E1 analogue that acts as a cytoprotectant, protecting cells from damage. [9] This drug can reduce inflammation in the gut and help ease some of the associated discomforts.

It has been shown to reduce the secretion of gastric acid in the stomach of horses. [13] Excessive acidity contributes to the formation of ulcers by eroding cells that line the intestinal tract.

Misoprostol has also been shown to improve intestinal barrier function in the gut of horses on NSAID medications. It helps to support the healing of the gastrointestinal mucosa following injury. [32]

Effects of NSAIDs

Pain-relieving NSAID medications – such as indomethacin, flunixin meglumine (banamine), and phenylbutazone (bute) – inhibit the enzyme cyclooxygenase-1 (COX-1). This enzyme is involved in pathways that activate inflammation following injury or infections.

In particular, the COX-1 enzymes make molecules called prostaglandins and thromboxane, which are involved in activating the immune system and causing a pain response.

Blocking COX-1 with NSAIDs is an effective way to relieve pain, inflammation and fever, which is why these drugs are commonly prescribed for horses with colic, arthritis or laminitis. Long-term use of NSAIDs may be required to provide comfort and improve the quality of life for these horses.

Prostaglandins and Gut Health

However, prostaglandins are also important for protecting cells of the digestive tract. The digestive tract is lined with a mucous barrier known as the mucosa. This blocks bacteria and toxins from being absorbed while allowing nutrients to pass into the blood.

Prostaglandins are involved in maintaining this defensive mucosal barrier and have several effects on the digestive tract, including: [3][4][5][6]

  • Increase blood flow in the mucosa by causing blood vessels to dilate
  • Raise mucosal bicarbonate secretion which helps to neutralize stomach acid
  • Decrease stomach acid production
  • Modulate immune responses

NSAIDs and Gut Injury

By blocking COX-1, NSAIDs suppress prostaglandin production, which compromises the mucosa’s ability to form a protective barrier between the environment inside the digestive tract and the cells lining it.

This allows stomach acidity and other irritants to cause inflammation, ulcers and bleeding throughout the gut.

In addition, NSAIDs will slow the recovery of pre-existing lesions by causing neutrophils to gather at the injury and exacerbate inflammation. [7][8]

COX-2-specific NSAIDs such as Equioxx and Previcox have been developed to lessen the digestive side effects of NSAID use. However, their long-term use may still induce injury in the small and large intestines. [31]

Ideally NSAIDs should be avoided in horses with pre-existing ulcers in the gut. However, these horses may develop conditions such as laminitis which require treatment with NSAIDs. Misoprostol may be applied concurrently with the NSAIDs to prevent ulcers from worsening. [7]

Mad About Horses
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