Taking a Closer Look at: Altrenogest
| May 11, 2026
Altrenogest, which is commercially sold as Regu-Mate, is an FDA-approved synthetic progesterone used to suppress estrus and seasonal behaviors in competing horses and aid in breeding practices with broodmares. Altrenogest, or any other progestogen, is also prohibited for use in stallions and geldings while competing in USEF-licensed competitions because it has no legitimate therapeutic use in male horses and has been historically used as a calming agent. The prohibition of altenogest, or any...







