The World Anti-Doping Agency (WADA) updates and publishes the Prohibited List each year.
This list is one from the International Standard that outlines:
The substances and methods that are prohibited in- and out-of-competition. The sports in which the substances and methods are prohibited.
WADA runs a consultation period through its List Expert Group and Health, Medical and Research Committee before preparing and publishing the Prohibited List. The Prohibited List is approved by WADA’s Executive Committee in September of each year and published three months before it comes into effect on 1 January.
For a substance or method to be prohibited, it must meet two of the following three conditions:
It has the potential to enhance, or it does enhance performance in sport. It has the potential or represents an actual risk to the athlete’s health. It violates the spirit of sport (this definition is described in the introduction to the Code).
See current WADA Prohibited List.