23 horse deaths led to progesterone drug ban by USEF


Medroxyprogesterone acetate (MPA) will be prohibited in horses competing in United States Equestrian Federation (USEF) events from December 1.

The move to prohibit the substance followed reviews in early 2017 and in October this year, after several horse fatalities were reported.

Starting December 1, 2019, MPA in horses competing at USEF-licensed competitions will be prohibited. However, due to the length of time involved for MPA to clear a horse’s system, sanctions for a positive test result will begin on June 1, 2020. The USEF has classified MPA as a Category III substance which has a penalty range starting at a 3-6 month suspension and a fine of $3000 to -$6000 for a first offence.

Medroxyprogesterone has been administered to performance mares with the intention of blocking behavioral estrus, and there also is some thought that progestins such as MPA may calm the behavior of “hot” horses and reduce stallion-like behavior in geldings. Depo-Provera is the brand name of the synthetic hormone used in human medicine as a method of birth control.

The USEF’s MPA Panel reviewed a recent petition by several veterinarians requesting that USEF ban the use of MPA which was supported by documentation citing 23 fatalities associated with MPA use over the last three years, research on the efficacy of the substance, and the results from the collection of MPA medication reports.

“In 2017, we debated the use of this substance and its efficacy, but now, with numerous fatalities associated with the use of MPA, this decision became clear: MPA must be banned,” said USEF President Murray Kessler.

“I commend the Panel for confronting a difficult task that involved very strong opinions on both sides of the issue from our membership. The information clearly supports the prohibition of this substance and I am proud of the decision of the Board of Directors. USEF has a responsibility to ensure the welfare of our horses, and the loss of one horse resulting from the use of a non-therapeutic substance such as MPA is one too many.”

The Panel, which met on October 22, determined that MPA has no therapeutic use in competition horses, as it does not interrupt estrus in mares, which predicated its original use. Additionally, MPA is not approved by the United States Food and Drug Administration (FDA) for use in equines.

The earlier review, in 2017, led to the Panel’s recommendation to require disclosure of MPA administration in competition horses from September 1, 2017. Since that date, pharmacokinetic data related to MPA administration has been collected and analyzed.


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