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Arimistane

Updated · 20 sources · Editorial policy

Arimistane is the trade name for androsta-3,5-diene-7,17-dione, a synthetic steroid sold in bodybuilding products as a “natural” or over-the-counter aromatase inhibitor. Aromatase is the enzyme that converts testosterone and androstenedione into estrogens. Products containing arimistane are marketed to lower estrogen, often for use after a course of anabolic steroids.

The most important fact is that no controlled human study has tested whether arimistane lowers estrogen or does anything else in people. The published human data come from anti-doping laboratories that gave single doses to a few volunteers to identify urinary metabolites. In 2018 the FDA told a US seller that arimistane is not a lawful dietary ingredient, and the World Anti-Doping Agency (WADA) bans it by name as an aromatase inhibitor.

This page summarizes what laboratory studies, doping-control research and regulators report. It is for education only and is not medical advice.

Property Detail
Chemical name Androsta-3,5-diene-7,17-dione; C₁₉H₂₄O₂, 284.4 g/mol; CAS 1420-49-1
Class Synthetic steroid marketed as an aromatase inhibitor; a “designer steroid” in FDA and USADA documents
Relation to 7-keto-DHEA Lacks the 3β-hydroxyl group of 7-keto-DHEA; forms from 7-keto-DHEA in acidic conditions and during some lab analyses
Route studied Oral, single 25 mg dose in 3 volunteers (metabolism study only)
Half-life Not reported in any published human study
Human efficacy trials None found (PubMed, ClinicalTrials.gov)
FDA position Not a dietary ingredient; product treated as an unapproved new drug (2018 warning letter)
US schedule Not listed as a Schedule III anabolic steroid
WADA status Prohibited at all times (S4.1, aromatase inhibitors); Specified Substance

What it is

Arimistane is a C19 steroid with ketone groups at carbons 7 and 17 and two double bonds in the A and B rings (between carbons 3–4 and 5–6) (PubChem CID 150910). It is closely related to 7-keto-DHEA, a natural metabolite of DHEA that is also sold as a supplement.

Compound Chemical name Formula Molecular weight
7-Keto-DHEA 3β-hydroxyandrost-5-ene-7,17-dione C₁₉H₂₆O₃ 302.4 g/mol
Arimistane Androsta-3,5-diene-7,17-dione C₁₉H₂₄O₂ 284.4 g/mol

Sources: PubChem CID 193313; PubChem CID 150910.

The two structures differ by one molecule of water: arimistane has no hydroxyl group at carbon 3 and instead carries an extra double bond. In acidic conditions, 7-keto-DHEA loses that hydroxyl and turns into arimistane. This has been known since 1971, when androsta-3,5-diene-7,17-dione was isolated from urine and shown to form from 7-keto-DHEA sulfate under various hydrolysis conditions (Schubert et al., Endocrinol Exp 1971).

Arimistane is not an approved medicine anywhere we could find. Unlike anastrozole and letrozole, which are nonsteroidal, it is a steroid, as is exemestane. However, it has never gone through the clinical development those drugs did.

How it works in the body

Claimed mechanism: aromatase inhibition

The case for arimistane as an aromatase inhibitor rests on test-tube chemistry, not human data. In a 1994 study, Numazawa and colleagues synthesized a series of androst-5-en-7-ones and androsta-3,5-dien-7-ones, the structural family arimistane belongs to, and tested them on aromatase from human placental microsomes (a lab preparation of the enzyme) (Numazawa et al., J Med Chem 1994). Key findings:

  • All the steroids in the series blocked the enzyme competitively, with inhibition constants (Ki) ranging from 0.058 to 45 µM across the series.
  • Compounds with a ketone at carbon 17 were much more potent than the matching 17β-alcohols.
  • Some 3,5-dien-7-ones also inactivated the enzyme over time when NADPH (a cofactor) was present.

The abstract does not give a separate potency figure for arimistane. No published study has measured estradiol, estrone or testosterone levels in people after taking arimistane.

Metabolism in humans

The Rome anti-doping laboratory (FMSI) gave a single oral dose to three healthy volunteers and analyzed their urine:

Study Method Main findings
Martinez Brito et al., Rapid Commun Mass Spectrom 2019 25 mg single oral dose, n = 3; GC with high-accuracy MS Up to 15 metabolites found only after dosing, mostly excreted as glucuronides. Arimistane itself appeared only in the sulfate fraction. No relevant effect on the urinary steroid profile after one dose.
Martinez Brito et al., Rapid Commun Mass Spectrom 2021 Same samples (up to 10 h after dosing); LC-MS 12 metabolites identified: 4 reduced, 4 monohydroxylated and 4 bis-hydroxylated. Arimistane itself was found in all three volunteers.

A 2015 report had proposed androst-3,5-diene-7β-ol-17-one as the main urinary metabolite, and the 2019 study corroborated it (Martinez Brito et al., 2021). The 2019 study found that the hydroxylated metabolites did not match 7-keto-DHEA or its 7-hydroxy forms, suggesting the body does not turn arimistane back into 7-keto-DHEA (Martinez Brito et al., 2019).

These studies were designed to detect use in sport. They did not measure blood levels, so no half-life has been published.

What the research shows

Human efficacy

We found no randomized or controlled human trial of arimistane for any outcome. A PubMed search for “arimistane” or its chemical name returns only doping-control, chemistry and supplement-analysis papers, and ClinicalTrials.gov lists no registered studies. Claims that it lowers estrogen, raises testosterone, or helps recovery after steroid use are not supported by published human data.

Arimistane and 7-keto-DHEA in drug testing

Because 7-keto-DHEA can turn into arimistane, labs had to work out whether finding arimistane in urine means someone took arimistane or 7-keto-DHEA:

  • Lab artifact. Common derivatization reagents used before gas chromatography (GC) convert reference 7-keto-DHEA into arimistane, and about 1% of 7α-hydroxy-DHEA also showed up as arimistane (Martinez-Brito et al., Rapid Commun Mass Spectrom 2020).
  • After 7-keto-DHEA dosing. In volunteers given 7-keto-DHEA, arimistane formation was most likely linked to sample preparation or instrument analysis. Isotope testing also showed that 7-keto-DHEA was not converted to DHEA (Martinez-Brito et al., Drug Test Anal 2019).
  • Degradation, not metabolism. 7-keto-DHEA degraded to arimistane when stored in methanol but stayed stable in DMSO. Human liver microsomes did not make arimistane from it. The authors concluded that arimistane is a useful marker of 7-keto-DHEA intake, but that it forms by degradation rather than by the body’s metabolism (Martínez Brito et al., Drug Test Anal 2021).

For labs, this means the specific arimistane metabolites described above, not arimistane alone, are what point to arimistane use.

Regulatory status

FDA: not a lawful dietary ingredient

In a May 18, 2018 warning letter to Performance Nutrition Formulators LLC (VMI Sports), FDA stated that androsta-3,5-diene-7,17-dione “is an aromatase inhibitor and does not constitute a dietary ingredient” under the Federal Food, Drug, and Cosmetic Act (FDA warning letter, 2018). The agency concluded that:

  • the product was not a dietary supplement, because it contained no dietary ingredient;
  • its label claims about managing estrogen and improving strength made it a drug;
  • it was an unapproved “new drug,” since it was not generally recognized as safe and effective;
  • it would be a prescription drug, because approved aromatase inhibitors are all limited to use under a licensed practitioner’s supervision.

USADA states that FDA has made the same point in numerous warning letters (USADA).

US military

Operation Supplement Safety (OPSS), the Department of Defense supplement-safety program, names arimistane as an example of an aromatase inhibitor in bodybuilding products. It states that these compounds are considered drugs, should not be in dietary supplements, and are on the DoD Prohibited Dietary Supplement Ingredients list (OPSS, updated 2022).

Controlled-substance status

Arimistane is not named in the DEA’s list of Schedule III anabolic steroids (21 CFR 1308.13). Its legal problem in the US is under drug and supplement law, not the Controlled Substances Act.

Sport

The 2026 WADA Prohibited List names “androsta-3,5-diene-7,17-dione (arimistane)” in class S4.1, aromatase inhibitors. It is prohibited at all times, in and out of competition, and S4.1 substances are Specified Substances (WADA 2026 Prohibited List). Its relative 7-keto-DHEA is banned under a different class, S1 anabolic agents.

Athletes have been sanctioned after taking supplements that listed it:

  • A UFC athlete received a 10-month sanction in 2019 after testing positive for arimistane and its metabolite 7β-hydroxy-androst-3,5-diene-17-one; USADA concluded the positive test was caused by a dietary supplement whose label listed the substance (USADA, 2019).
  • In a 2016 track-and-field case, USADA found the athlete had bought one supplement containing ostarine and another containing arimistane; she received a one-year period of ineligibility (USADA).

Quality and contamination

Arimistane turns up both as a labeled ingredient and as an undeclared one:

  • Identified by the FDA lab. The FDA Forensic Chemistry Center found an unknown steroid in a supplement marketed for “performance enhancement” and identified it as androsta-3,5-diene-7,17-dione. It later found the same compound in a second product that contained three other active ingredients (Lorenz et al., Drug Test Anal 2019).
  • Hidden in other products. Among 12 supplements labeled to contain 5α-hydroxy-laxogenin, one contained arimistane that was not on the label (Avula et al., J Pharm Biomed Anal 2019).
  • Mislabeled multi-ingredient products. In 4 supplements listed in the NIH Dietary Supplement Label Database as containing 5α-hydroxy-laxogenin, none was accurately labeled overall. One product declared 75 mg of androst-3,5-diene-7,17-dione per maximum daily serving and contained 71.8 mg (Cohen et al., JAMA Netw Open 2020).

A Polish medicines-control laboratory screened 601 seized performance-enhancing drug samples (2020–2024) for all WADA-listed aromatase inhibitors, including arimistane. The only aromatase inhibitors it identified were letrozole, anastrozole and exemestane (Blazewicz et al., Front Chem 2025).

Side effects and risks

No human safety data

No study has reported side effects, organ safety or interactions for arimistane in people. The only published human exposures are single 25 mg doses in three volunteers, which were not designed to assess safety (Martinez Brito et al., 2019).

Risks FDA attributes to aromatase inhibitors as a class

In its warning letter, FDA listed adverse events associated with FDA-approved aromatase inhibitors: decreased rate of bone maturation and growth, decreased sperm production, infertility, aggressive behavior, adrenal insufficiency, kidney failure and liver dysfunction (FDA warning letter, 2018). USADA lists bone loss, joint pain and autoimmune rheumatic disease as common side effects of aromatase inhibitors (USADA). Whether arimistane causes any of these is unknown, because its effect on estrogen in people has never been measured. The labeled risks of the approved drugs are covered on the anastrozole, letrozole and exemestane pages.

Product and testing risks

  • Uncertain contents. Supplement analyses have found arimistane undeclared in some products and other ingredients missing or misdosed in products that list it.
  • Positive doping tests. Athletes subject to WADA rules can be sanctioned for arimistane even when it is listed on a supplement label, as the USADA cases above show.

Key takeaways

  • A steroid sold as a supplement aromatase inhibitor. Arimistane (androsta-3,5-diene-7,17-dione) is marketed to lower estrogen, but it is not an approved drug.
  • Close chemical relative of 7-keto-DHEA. It is 7-keto-DHEA without the 3-hydroxyl group, and 7-keto-DHEA can degrade into it in acid or during lab analysis.
  • No human efficacy data. Its aromatase-blocking claim rests on 1990s enzyme studies of related compounds; no study has measured hormone changes in people.
  • Human research is limited to doping control. Single 25 mg doses in three volunteers were used to identify urinary metabolites; no half-life or safety data exist.
  • Not a lawful supplement ingredient in the US. FDA’s 2018 warning letter said it is not a dietary ingredient and treated the product as an unapproved new drug.
  • Banned in sport. WADA lists arimistane by name under S4.1 aromatase inhibitors, prohibited at all times, and athletes have been sanctioned after using supplements containing it.

Sources

  1. National Center for Biotechnology Information. Androsta-3,5-diene-7,17-dione (arimistane), CID 150910. PubChem.
  2. National Center for Biotechnology Information. 7-Keto-DHEA, CID 193313. PubChem.
  3. Schubert K, Wehrberger K, Hobe G. Androsta-3,5-diene-7,17-dione: isolation from urine and formation from 7-keto-dehydro-epiandrosterone sulphate under various conditions of hydrolysis. Endocrinol Exp. 1971;5(4):205–210. PubMed.
  4. Numazawa M, Mutsumi A, Tachibana M, Hoshi K. Synthesis of androst-5-en-7-ones and androsta-3,5-dien-7-ones and their related 7-deoxy analogs as conformational and catalytic probes for the active site of aromatase. J Med Chem. 1994;37(14):2198–2205. PubMed.
  5. Martinez Brito D, de la Torre X, Botrè F. Detection of urinary metabolites of arimistane in humans by gas chromatography coupled to high-accuracy mass spectrometry for antidoping analyses. Rapid Commun Mass Spectrom. 2019;33(24):1894–1905. PubMed.
  6. Martinez Brito D, Leogrande P, Botrè F, de la Torre X. 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;35(12):e9080. PubMed.
  7. Martinez-Brito D, de la Torre X, Parr MK, Botrè F. Mass spectrometric analysis of 7-oxygenated androst-5-ene structures. Influence in trimethylsilyl derivative formation. Rapid Commun Mass Spectrom. 2020;34(17):e8834. PubMed.
  8. Martinez-Brito D, de la Torre X, Colamonici C, Curcio D, Botrè F. 7-keto-DHEA metabolism in humans. Pitfalls in interpreting the analytical results in the antidoping field. Drug Test Anal. 2019;11(11-12):1629–1643. PubMed.
  9. Martínez Brito D, Leogrande P, Colamonici C, Curcio D, Botre F, de la Torre X. Arimistane: degradation product or metabolite of 7-oxo-DHEA? Drug Test Anal. 2021;13(7):1430–1439. PubMed.
  10. US Food and Drug Administration. Warning letter to Performance Nutrition Formulators LLC dba VMI Sports, MARCS-CMS 543959. May 18, 2018. FDA.
  11. Operation Supplement Safety (Uniformed Services University). Aromatase inhibitors: can military service members use them? Updated April 25, 2022. OPSS.
  12. US Drug Enforcement Administration. Schedules of controlled substances: Schedule III. 21 CFR 1308.13. eCFR.
  13. World Anti-Doping Agency. 2026 Prohibited List (in effect January 1, 2026). WADA 2026 Prohibited List.
  14. US Anti-Doping Agency. Aromatase inhibitors. USADA.
  15. US Anti-Doping Agency. Yaozong Hu accepts sanction for violation of UFC Anti-Doping Policy. June 14, 2019. USADA.
  16. US Anti-Doping Agency. Imani Oliver accepts doping sanction. USADA.
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