Trainers should be aware that the use of altrenogest (trade name 'Regumate') may pose a risk of a positive finding for trenbolone or trendione.

Altrenogest is considered by the ARCI as a Class 4/C substance in geldings, colts, and horses. While the regulation of altrenogest is specific to each jurisdiction, in Indiana altrenogest remains a non-violation in fillies and mares.

Trainers are recommended to use caution when using altrenogest and consider saving samples from any altrenogest containers until all post-race tests from sampled horses have been completed.

(Indiana Horse Racing Commission)