Competition horse deaths spur analysis on Medroxyprogesterone


Update: 23 horse deaths led to progesterone drug ban by USEF

The use of the synthetic progesterone Medroxyprogesterone acetate (MPA) in horses is under analysis by the US Equestrian Federation over “a number of recently reported equine fatalities”.

The USEF is reconvening its MPA Panel to further analyze the use of Medroxyprogesterone in horses competing at USEF-licensed competitions.

Depo-Provera is the brand name of the synthetic hormone used in human medicine as a method of birth control. 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.

“This latest information on equine fatalities associated with the use of MPA underscores the need for the MPA Panel to meet and review the critical information about this substance in order to provide our members with the information they need to protect their equine partners,” the USEF said.

The MPA Panel was first convened in the winter to 2017 due to discussion in the veterinary community and the emergence of research regarding the efficacy of MPA in competition horses. Specifically, the question focused on how MPA affects the competition horse, since research indicated that MPA does not interrupt estrus in mares. This was especially important due to its increased use in geldings and stallions, and also to the reports of increased dosages being administered.

Following discussions at public hearings and town halls, as well as feedback from members, the MPA Panel recommended that the use of MPA continued to be monitored, including implementation of MPA-specific medication reports in order to capture more information on dosage, administration schedules, and the continued presence of the substance in a horse’s system after the last known administration.

“However, the recent reports of equine fatalities has raised greater concern regarding the safety of this substance in horses,” the USEF said.

In the interim, the federation “strongly discourages the use of MPA”, and recommends consultation with a veterinarian.

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