Fluoxymesterone

Fluoxymesterone is a synthetic anabolic‑androgenic steroid (AAS) marketed under the brand name Halotestin. It is an orally active, 17α‑alkylated androgen that has been used medically for select indications, including androgen replacement therapy in men with testosterone deficiency when other forms are unsuitable, and as palliative treatment for metastatic breast cancer in women. It is not a first‑line therapy and is used with caution due to safety concerns.

Mechanism and administration: Fluoxymesterone exerts its effects by binding to androgen receptors, promoting protein synthesis and the development of male secondary sexual characteristics. The 17α‑alkylation allows oral activity but increases the risk of liver toxicity. Dosing is individualized and must be supervised by a clinician.

Side effects and safety: Adverse effects include virilization in women and children (deepening of the voice, hirsutism, menstrual disturbances), acne, scalp hair loss, edema, and unfavorable changes in lipid profiles. Hepatotoxicity, cholestasis, and rare liver tumors are concerns with 17α‑alkylated androgens. Psychiatric effects and electrolyte disturbances may occur. Fluoxymesterone is contraindicated in pregnancy, in men or women with androgen‑dependent cancers, and in individuals with significant liver disease or cardiovascular risk. Caution is advised in older adults and those with polycythemia.

Regulatory status and history: Fluoxymesterone is a controlled substance in many jurisdictions due to abuse potential and is available by prescription only. It is banned in competitive sports by major anti‑doping organizations.