The verdict
Our read at a glance.
Whether a short-term subjective effect on aggression justifies the most severe hepatic profile in the class.
- The signal
- Fluoxymesterone had genuine approved uses - androgen replacement in men and palliative treatment of breast cancer in women - and appears in the older clinical literature in those roles, including in registered oncology work. It has essentially disappeared from modern therapeutic use, displaced by better-tolerated options. There is no controlled study of the acute psychological or strength effect it is now taken for; that claim rests entirely on user report. What is documented is its hepatic profile, which is severe even by the standards of 17-alpha-alkylated orals.
- The unknown
- Whether the aggression effect is pharmacological or expectancy. It has never been tested, and it is used in exactly the settings where expectation and arousal are already maximal.
- Our read
- Taken for a feeling, at a hepatic cost that is documented and large. The strength claim has never been measured, the aggression claim has never been measured, and the liver findings are the only part of this compound's file that is not anecdote.
The mechanism
How it works.
Fluoxymesterone is testosterone with three modifications: a fluorine at position 9, a hydroxyl at position 11, and a 17-alpha methyl group. The fluorine and hydroxyl substitutions raise androgen receptor affinity substantially and block aromatisation, so it is a powerful, purely androgenic agent producing no oestradiol. The 17-alpha methyl group makes it orally active and is responsible for the hepatic toxicity, which is unusually severe here because the compound is both highly resistant to metabolism and taken orally. The acute effects users describe - aggression, confidence, perceived strength - are generally attributed to rapid central androgen receptor activation, but no controlled study has measured behaviour, mood or performance after administration, so that mechanism remains an explanation for an unverified observation.
Safety & regulatory boundary
The consequential part.
A Schedule III controlled substance with no meaningful current therapeutic use. It is 17-alpha-alkylated and highly androgenic, with a hepatotoxicity profile that includes cholestasis, peliosis hepatis and hepatic tumours in the older literature, and it suppresses HDL severely. Non-aromatising, so it offers none of oestrogen's compensating effects. Prohibited in sport.
What's next
What we're watching.
Nothing in development. The relevant surveillance is hepatic case reporting.
Context
Why this is discussed.
It has a reputation for producing strength and aggression acutely, which makes it attractive immediately before competition rather than as part of a longer cycle.
The evidence base
20 cited references.
Registered trials8
ClinicalTrials.gov · ACTIVE_NOT_RECRUITING · 2024-01-17
ClinicalTrials.gov · NOT_YET_RECRUITING · 2026-08-01
ClinicalTrials.gov · NA · NOT_YET_RECRUITING · 2027-01-01
ClinicalTrials.gov · NA · NOT_YET_RECRUITING · 2026-09
ClinicalTrials.gov · NA · NOT_YET_RECRUITING · 2026-10-01
ClinicalTrials.gov · PHASE2 · NOT_YET_RECRUITING · 2026-07-01
ClinicalTrials.gov · NA · COMPLETED · 2025-10-08
ClinicalTrials.gov · NA · NOT_YET_RECRUITING · 2026-07-01
Indexed literature (PubMed)12
J Am Med Assoc · J Am Med Assoc · 1957
BUCKLE RM · Br Med J · 1959
Lo TE et al. · BMJ Case Rep · 2015
Lenko HL et al. · Acta Paediatr Scand · 1982
HUDSON B · Med J Aust · 1959
Vomachka AJ et al. · Dev Psychobiol · 1981
Kono M et al. · Breast Cancer Res Treat · 2016
KENNEDY BJ · N Engl J Med · 1958
Jones TM et al. · J Clin Endocrinol Metab · 1977
PERGOLA F · Dia Med · 1959
Tormey DC et al. · Ann Intern Med · 1983
PASETTO N · Riv Ostet Ginecol Prat · 1959
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