International Prohibited / Forbidden Substance Thresholds


The International Federation of Horseracing Authorities have established international thresholds for:

  • substances endogenous to the horse
  • substances arising from plants traditionally grazed or harvested as equine feed
  • substances in equine feed arising from contamination during cultivation, processing or treatment, storage, or transportation

As an International Federation of Horseracing Authorities member the National Horseracing Authority of Southern Africa applies these thresholds / concentrations which are provided below.


  • 0.3 microgram total arsenic per millilitre in urine


  • 0.015 microgram free and conjugated boldenone per millilitre in urine from male horses (other than geldings)

Carbon dioxide

  • 36 millimoles available carbon dioxide per litre in plasma


  • 0.1 microgram total cobalt per millilitre in urine
  • 0.025 microgram total cobalt (free and protein bound) per millilitre in plasma

Dimethyl sulphoxide

  • 15 micrograms dimethyl sulphoxide per millilitre in urine, or
  • 1 microgram dimethyl sulphoxide per millilitre in plasma

Estranediol in male horses
(other than geldings)

  • 0.045 microgram free and glucuroconjugated 5α-estrane-3β,17α-diol per millilitre in urine


  • 1 microgram hydrocortisone per millilitre in urine


  • 4 micrograms free and conjugated 3-methoxytyramine per millilitre in urine

Salicylic acid

  • 750 micrograms salicylic acid per millilitre in urine, or
  • 6.5 micrograms salicylic acid per millilitre in plasma


  • 0.02 microgram free and conjugated testosterone per millilitre in urine from geldings, or
  • 0.055 microgram free and conjugated testosterone per millilitre in urine from fillies and mares (unless in foal)
  • 100 picograms free testosterone per millilitre in plasma from geldings, fillies and mares (unless in foal)


  • 0.01 microgram free prednisolone per millilitre in urine

The conjugated substance is the substance that can be liberated from conjugates.
The free substance is the substance which is not conjugated (which is unconjugated).
Each threshold, including those for the same substance in urine and plasma, can be applied independently.

The concentrations listed above have been determined to be the maximum concentration permitted in a specimen taken from any horse.
In terms of Rules 73.4 and Rule 74 the abovementioned substances shall be prohibited substances if the concentration found in a specimen exceeds the concentration set out above.

Application of International Threshold Values to Out of Competition Testing collected specimens

International threshold values for Arsenic, Boldenone, Carbon dioxide, Cobalt, Dimethylsulfoxide (DMSO), Estranediol, Hydrocortisone, Methoxytyramine, Prednisolone, Salicylic Acid and Testosterone are applicable to Out of Competition Testing (OOCT) collected specimens. For those substances which are not Forbidden Substances these may not be actionable if a legitimate treatment is appropriately recorded in the relevant Veterinary Treatment Register.