News & Press: NZVA news

Notice to cease using Altrenogest Injections in Racehorses

Thursday, 20 September 2018  
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Update: 29 October 2018
Please see the following news story for updated information.

Notice: Using oral Altrenogest in racehorses


Veterinarians are advised to stop using all injectable forms of Altrenogest in racehorses from now on.

This decision has been made because the anabolic steriods Trenbolone and Trienolone have been detected in post race urine samples in Australia from the use of Altrenogest injections.Trenbolone and Trienolone are impurities found in very low concentrations following  the manufacture of the Altrenogest raw material.


Altrenogest is exempt under the Prohibited Substance Regulations when used in females.
Altrenogest is a powerful progestin of the 19- nortesterone group with the chemical name of allytrenbolone. However both Trenbolone and Trienolone are anabolic steroids and prohibited substances under both HRNZ and NZTR Prohibited Substance Regulations.

The use of Altrenogest in the oral form has been extensively used for decades and was first
licensed by the ACVM in 1982. To date there has never been any Trenbolone or Trienolone detected in post race urine samples when using oral Altrenogest and a possible reason could be  Trenbolone and Trienolone are poorly absorbed by the oral route.Two injection formulations were  licensed by the ACVM in November 2017.


  1. Cease using Altrenogest Injections in racing females.
  2. When using oral Altrenogest in racing females use the listed label dose rate. Do not double  dose.
  3. Stop using oral Altrenogest in racing females ‘one clear day’ from racing.