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Medical use

Tamoxifen belongs to the substances that regulate the function of estrogen receptors (Selective Estrogen Receptor Modulators, SERM). It is an anti-estrogenic medical substance that is used for breast cancer treatment.


Tamoxifen is a doping substance according to the Decree 705/2002 that defines the doping substances that are to be regarded as doping substances referred to in Chapter 44, §16, Subsection 1 of the Penal Code.

By using tamoxifen, abusers of anabolic steroids are trying to prevent the estrogenic harm caused by anabolic steroids, such as the overgrowth of breasts (gynecomastia) and blood clots.

Adverse effects

The adverse effects of tamoxifen include nausea, vomiting, swelling and dermatitis. Patients who receive tamoxifen treatment have been found to develop visual disturbances such as changes in the cornea, cataracts, and retinopathia (diabetic retinal disease). For that reason, the eyes of the patients who use tamoxifen should be checked regularly with eyeground examinations.

The long-term use of tamoxifen is suspected to increase the risk of some cancers. In women, tamoxifen causes menstrual disturbances [1].

Timo Seppälä
Medical Director
The Finnish Antidoping Agency FINADA

[1] Jordan (2008): Tamoxifen: catalyst for the change to targeted therapy. European Journal of Cancer 44(1): 30–8.

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