The substance Anastrozole is a class S4.1 substance under the World Anti-Doping Code Prohibited List 2021. Anastrozole is classified as a Specified Substance and is prohibited at all times.

Anastrozole is a hormone and metabolic modulator prescribed to treat early breast cancer.

As the use of hormone and metabolic modulators interferes with the normal functioning nature of hormones, the endocrine system that controls these hormones is significantly impacted. This interferes can therefore increases the risk of severe illnesses.