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U.S. Department of Health and Human Services

Animal & Veterinary

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FDA Approves Life-Saving Horse Drug

by Lynne Oliver, DVM and Melanie McLean, DVM, Center for Veterinary Medicine, FDA

Led by the Office of New Animal Drug Evaluation (ONADE), FDA’s Center for Veterinary Medicine recently approved EQUIDONE (domperidone) Gel for the prevention of fescue toxicosis in pregnant mares. The approval of EQUIDONE Gel is important to the horse world because it’s the first FDA-approved drug to prevent the devastating effects of fescue toxicosis.

The Cause

Fescue toxicosis occurs when pregnant mares eat tall fescue grass or hay infected with an endophytic fungus, Neotyphodium coenophialum (previously known as Acremonium coenophialum). The fungus isn’t visible because it lives within the cells of the fescue plant. The fungus produces a group of chemicals called alkaloids. The alkaloids in the fungus are beneficial to the fescue grass, making the plant more hardy and resistant to parasites, drought, and overgrazing. The alkaloids are also toxic to horses, interfering with the hormones involved in pregnancy and milk production.

The Effects

Fescue toxicosis results in severe, even life-threatening, reproductive problems in both mares and foals around the time of birth. These problems include:

  • increased length of pregnancy
  • difficulty giving birth
  • lack of milk production
  • abortions
  • separated or thickened placentas
  • stillborn foals
  • foals born weak or not fully matured
  • increased mare and foal mortality.

The Concern

Fescue toxicosis is a big concern for horse owners because tall fescue is widespread in the United States. The grass is commonly found in pastures and hay. There are about 35 million acres of tall fescue in the United States, with about 700,000 horses grazing these pastures. Some management practices, such as removing mares from infected pastures during the last trimester of pregnancy, reduce the frequency and severity of fescue toxicosis. But, there was no FDA-approved drug to prevent the disease. Now there is.

FDA Approval

Veterinarians can prescribe EQUIDONE Gel for a mare at-risk for fescue toxicosis. The drug is an oral gel given once daily starting 10 to 15 days before the mare’s expected due date. She may continue to be treated up to 5 days after giving birth. The active ingredient in EQUIDONE Gel, domperidone, works by binding to the receptor sites where the alkaloid toxins normally bind. By filling up the receptor sites throughout the mare’s body, the drug blocks the toxins from binding so they can’t do damage.

To gain FDA-approval for EQUIDONE Gel, the drug company (Dechra Veterinary Products in Overland Park, KS) conducted studies to show that the drug is safe, effective, and high-quality. FDA’s approval means EQUIDONE Gel is safe and effective in mares when it is used according to the label. FDA’s approval also ensures that the drug’s strength, quality, and purity are consistent from batch to batch, and that the label is appropriate and truthful.

With FDA-approved EQUIDONE Gel, the 35 million acres of fescue pastures in the United States are a safer place for pregnant mares and their foals. Horse owners can breathe a sigh of relief.