Arimistane

A steroidal aromatase inhibitor that sold for years as a legal "PCT supplement" — the over-the-counter cousin of exemestane, common in post-SARM stacks and hormone products aimed at gym-store shelves.

Arimistane (androsta-3,5-diene-7,17-dione) is an inadequately characterised synthetic steroidal compound marketed for aromatase inhibition. Non-clinical and chemical literature reports it inhibits aromatase irreversibly, meaning recovery would require new enzyme synthesis — that is reported rather than clinically validated in humans. The regulatory reality matters more than the pharmacology here: FDA concluded it is not a lawful dietary ingredient and could not establish it as generally recognised as safe, so its use in food products is adulterating; products marketed with aromatase-inhibition or treatment claims may additionally be unapproved new drugs.

Human efficacy and safety data are inadequate — its estrogen-lowering activity is inferred from structural chemistry and community bloodwork, not trials. It is prohibited in sport.

• NONE SHOWN. There is no controlled human trial of arimistane for any outcome — not oestrogen suppression, not body composition, not recovery after steroid use.
• The claims made for it are extrapolated from its structural class and from the behaviour of pharmaceutical aromatase inhibitors, which have completely different evidence bases.
• It has been a recurring subject of FDA enforcement action against supplement manufacturers.
• Where prescription aromatase inhibitors have real evidence, that evidence comes with real documented harms — bone density loss, fractures, joint pain — and there is no reason to assume an unstudied compound acting on the same enzyme avoids them.
• Because it is sold as a supplement, it is frequently taken without any measurement of oestrogen at all, which means people are suppressing a hormone they never established was high.

Orally taken. No adequate clinical pharmacokinetic, efficacy or safety characterisation exists — the only human data FDA identified is an extremely limited metabolism and doping-detection study in three volunteers. If the reported irreversible binding is accurate, recovery would depend on new enzyme synthesis rather than drug clearance, which would make an overshoot slower to correct. That is an inference, not a measured property.

The adverse effects of excessive estrogen suppression documented for prescription aromatase inhibitors (joints, libido, mood, lipids, bone) are plausible risks here too, not documented outcomes — with the added problem that actual content of supplement-era products was famously variable. The FDA has moved against it as an unapproved new drug.

• Everyone, in the sense that there is no validated indication, dose or monitoring strategy for it
• Anyone pregnant, breastfeeding or who could become pregnant, given reproductive and developmental concerns
• Adolescents, given concerns about bone and pubertal development
• Anyone with liver or kidney impairment
• Anyone with osteoporosis or bone-density risk factors
• Anyone in tested sport, where aromatase inhibitors are prohibited
• Anyone pregnant or who could become pregnant
• Anyone treating an unapproved compound as a substitute for clinician-managed care

• Other aromatase inhibitors or oestrogen-lowering agents, where suppression compounds.
• Tested sport, where aromatase inhibitors are prohibited as hormone modulators.
• No characterised human interaction profile otherwise.

• There is no validated indication for this compound, no safe-use protocol, no target laboratory range and no monitoring strategy — so this entry does not supply one. A lab result cannot legitimise unsupervised use of an uncharacterised unapproved drug.
• FDA identifies a wide range of theoretical concerns that go well beyond joints and libido: reproductive and developmental toxicity, effects on sperm and fertility, bone and pubertal development, liver and kidney dysfunction, adrenal effects, lipid changes and behavioural effects.
• Any exposure or symptom warrants clinician assessment. Tell them what you took, since it will not appear on a medication list otherwise.

If the reported irreversible binding is accurate, aromatase activity would return through new enzyme synthesis rather than drug clearance — nothing about that has been measured in a person. Anyone who has been taking it, for any length of time, should raise that with a clinician rather than assume anything about recovery, because none of it has been characterised.

US: FDA-warned unapproved ingredient — not legally a dietary supplement; WADA-banned.

Papers about this compound, not proof of the claims above. A title says what was studied, which is sometimes a negative result or a different question entirely.

• Arimistane: Degradation product or metabolite of 7-oxo-DHEA?
  Drug Test Anal, 2021
• Detection of urinary arimistane metabolites in humans using liquid chromatography-mass spectrometry: Complementary results to gas chromatography mass spectrometric data and its application to antidoping analyses
  Rapid Commun Mass Spectrom, 2021

• Arimistane: Degradation product or metabolite of 7-oxo-DHEA?Drug Test Anal · 2021
• Detection of urinary arimistane metabolites in humans using liquid chromatography-mass spectrometry: Complementary results to gas chromatography mass spectrometric data and its application to antidoping analysesRapid Commun Mass Spectrom · 2021
• Detection of urinary metabolites of arimistane in humans by gas chromatography coupled to high-accuracy mass spectrometry for antidoping analysesRapid Commun Mass Spectrom · 2019
• 7-keto-DHEAmetabolism in humans. Pitfalls in interpreting the analytical results in the antidoping fieldDrug Test Anal · 2019
• Mass spectrometric analysis of 7-oxygenated androst-5-ene structures. Influence in trimethylsilyl derivative formationRapid Commun Mass Spectrom · 2020
• The power of hyphenated chromatography-Time of flight mass spectrometry for unequivocal identification of spirostanes in bodybuilding dietary supplementsJ Pharm Biomed Anal · 2019