As many people will know, the anabolic steroids trendione and/or trenbolone have recently been detected in altrenogest oral solutions including the licensed veterinary product ‘Regumate® Equine 2.2mg/ml Oral Solution for Horses’. The presence of these steroids was first detected by Racing Victoria, Australia where altrenogest was not a prohibited substance when administrated to fillies or mares.
Initially the positive test results were thought to be due to contamination of a batch of oral altrenogest produced for the Southern Hemisphere.  However, extremely sensitive analysis of ‘Regumate® Equine 2.2 mg/ml Oral Solution for Horses’ has since detected the presence of trendione amongst the metabolites, residues and other impurities that make up <1% of the altrenogest. The manufacture of Regumate® Equine in the European Union complies with all of the specifications on contaminants and impurities and there has been no change in the quality of the product.  Altrenogest (which is the active component of Regumate®) and trendione both have a steroid structure. Trendione is one of the main metabolites of trenbolone and is considered to be a prohormone with limited activity. Horses do not break down altrenogest to trenbolone or trendione. 
In light of this information the BHA and the FEI have taken differing stances on the continued usage of altrenogest.  Whilst this creates confusion for UK vets we should pity our racehorse colleagues “Down Under”; they are facing a situation where the authorities from Racing Victoria and Racing NSW have each implemented significantly different rule amendments one completely banning altrenogest use in racehorses, the other not...
• The BHA have stated “at this time, we would advise trainers and other industry participants to remove Regumate® Equine from all licensed premises, and not to administer this product”, effectively prohibiting further usage in any animals that may compete on a racecourse (including young stock).   
• The FEI have stated that “with the currently available information, it is permissible to continue to use altrenogest product Regumate® Solution 2.2 mg/mL for mares as per the manufacturer’s instructions”, effectively allowing continued usage during competition.
With the use of anabolic steroids being prohibited in both racing and equestrian sports, these differing stances was confusing to our members and, at a recent BEVA Equestrian Sports Committee meeting, some reasoning for the relevant parties’ positions was sought:
The BHA is responsible for the integrity of racing and is accountable to a wagering/gambling public. As such the use of anabolic steroids, even at very low levels, is prohibited at all times under BHA rules (Schedule (G)1 of the BHA Rules of Racing). Therefore, with this new information regarding altrenogest now available, the BHA had no option but to prohibit usage until and unless more information becomes available. The BHA would not be permitted to break their own rules.
The FEI comes from a different starting point; it specifically permits the usage of altrenogest for mares with oestrus related behavioural problems, if relevant conditions are met. The FEI is aware of the importance of the product in allowing significant numbers of horses to compete and the implications of removing access to the product. In addition, under their constitution, the FEI is not permitted to make ad hoc rule changes except on welfare grounds.  Any changes of medication rules or general rule changes happen on the 1st January each year. 
Significant further work is ongoing on by all parties, including the manufacturers, and so it is likely that further amendments/clarifications could be made in the coming months.
BEVA will do our best to ensure prompt announcements of any changes to the regulations or guidance.