In the midst of the endurance crisis, the FEI has expanded its banned drugs list.

Ammonium chloride, a hard-to-detect substance associated with nerve-blocking, joins the FEI’s banned substance list from 1 January.

The FEI told H&H it had no specific reason for banning the substance, though its clean sport website highlights its “potential for abuse as a nerve-blocking agent”.

The FEI said it has received no official reports of illegal nerve-blocking in endurance vetgates, despite widespread comment on endurance forums.

Recently, top European daily papers Le Monde and Le Matin quoted vets who alleged undetectable cobra venom and a plant extract called Sarapin is also used.

Other medication control changes include two additions to the controlled list: Metformin, an antidiabetic drug with a potential welfare risk; and Levothyroxine, an exogenous thyroid hormone replacement.

Adrenocortico-trophic hormone (ACTH) moves from the banned list to controlled due to its therapeutic value.

Gamma-Butyrolactone (GBL) and Gamma-Hydroxybutyrate (GHB) are also both now prohibited, as both have potential to elevate growth hormones.