What is arimistane and Why is it Prohibited in Sports?

October 5, 2025 •

4 min read

Despite being marketed as a dietary supplement, arimistane is classified as a synthetic anabolic-androgenic steroid and is explicitly banned by the World Anti-Doping Agency (WADA). It functions as an aromatase inhibitor, and understanding what is arimistane involves examining its deceptive marketing and the significant health risks associated with its unapproved use.

Quick Summary

Arimistane is a synthetic steroid and banned aromatase inhibitor often sold deceptively as a dietary supplement. It reduces estrogen conversion but carries significant health risks and lacks FDA approval as a supplement ingredient.

Key Points

Banned Substance: Arimistane is a WADA-prohibited synthetic steroid and aromatase inhibitor, and is banned in all competitive sports.
Not a Legal Supplement: The FDA has issued warning letters stating arimistane is not a legal dietary ingredient and is considered an unapproved new drug.
Aromatase Inhibitor: It functions as a "suicide inhibitor" by permanently blocking the aromatase enzyme, reducing estrogen conversion.
Serious Health Risks: Use is associated with potential liver and kidney damage, decreased bone mineral density, and other severe side effects.
Misleading Marketing: Although sold to bodybuilders for hormone balance and post-cycle therapy (PCT), its use is unsafe, unproven by scientific evidence, and prohibited in sports.
Designer Steroid: The chemical name for arimistane, Androsta-3,5-diene-7,17-dione, confirms its classification as a synthetic anabolic-androgenic steroid.
No Safe Use: There is not enough reliable information to determine safe use, and medical professionals warn against its ingestion.

Arimistane, also known by its chemical name Androsta-3,5-diene-7,17-dione, is a synthetic anabolic-androgenic steroid. It gained popularity in bodybuilding circles as an aromatase inhibitor (AI), a compound that blocks the enzyme responsible for converting male hormones (androgens) into female hormones (estrogens). Its rise in popularity was largely fueled by its online availability as a "dietary supplement," despite strong evidence of its illegality and potential health dangers. While many users sought to control estrogen-related side effects from anabolic steroid cycles or to increase testosterone, regulatory bodies like the FDA and WADA have taken firm action against it.

The Role of Aromatase and its Inhibition

Aromatase is a crucial enzyme in the steroid synthesis pathway. It converts androgens, specifically testosterone, into estrogens. The balance between androgens and estrogens is essential for proper physiological function in both males and females. In males, excess estrogen can lead to undesirable side effects, such as gynecomastia (enlarged male breast tissue), bloating, and low libido. Aromatase inhibitors are designed to disrupt this conversion process.

The Mechanism of Arimistane

Arimistane is classified as a "suicide inhibitor" of the aromatase enzyme. This means it irreversibly binds to the enzyme's active site, permanently deactivating it. This action effectively reduces the number of active aromatase enzymes available in the body, which, in turn, decreases the conversion of testosterone to estrogen. The irreversible nature of its binding distinguishes it from non-steroidal inhibitors that can release from the enzyme, potentially allowing estrogen levels to rebound. However, this potent action comes with significant and unpredictable risks.

The Banned Substance and Regulatory Status

Arimistane's reputation shifted dramatically due to its classification by major regulatory bodies. It is not an approved medical drug but a synthetic steroid often mislabeled as a dietary supplement.

World Anti-Doping Agency (WADA) Ban

Since 2017, arimistane has been on the World Anti-Doping Agency's (WADA) Prohibited List. It is categorized as a Hormone and Metabolic Modulator, meaning its use is forbidden in all competitive sports, both in-competition and out-of-competition. This ban is a direct response to its ability to artificially manipulate hormone levels, giving athletes an unfair performance-enhancing advantage.

FDA Action and Legal Status

The U.S. Food and Drug Administration (FDA) has explicitly stated that arimistane is not a legal dietary ingredient. The agency has sent warning letters to companies selling products containing Androsta-3,5-diene-7,17-dione, declaring that these products are adulterated and misbranded. The FDA considers arimistane an unapproved new drug and a misbranded prescription drug because it cannot be used safely without the supervision of a licensed practitioner.

Purported Uses and Misleading Marketing

Online retailers and supplement manufacturers have aggressively marketed arimistane for several unproven uses, primarily targeting the bodybuilding and fitness communities. These purported benefits include:

Post-Cycle Therapy (PCT): Following a cycle of anabolic steroids, PCT is used to help restore the body's natural hormone production. Arimistane is sold for this purpose, claiming to help balance hormones and prevent estrogen rebound.
Testosterone Boosting: By blocking the conversion of testosterone to estrogen, it is marketed as a way to increase the body's free and total testosterone levels.
Body Composition and Aesthetics: Promoters claim it can create a 'harder,' more defined physique by reducing subcutaneous water retention and body fat.

Significant Health Risks and Side Effects

Given its status as a synthetic steroid and unapproved drug, arimistane's side effects are not well-studied in humans. However, based on its mechanism and the documented risks of other similar substances, several dangerous health effects have been identified.

Potential Adverse Effects

Liver and Kidney Damage: Reported side effects include damage to both the liver and kidneys, potentially leading to long-term dysfunction.
Decreased Bone Mineral Density: Aromatase inhibitors can lead to a reduction in bone mineral density, increasing the risk of osteoporosis and fractures, especially with prolonged use.
Hormonal Imbalances: While intended to modulate hormones, the unregulated inhibition of estrogen can lead to significant and potentially harmful hormonal imbalances.
Behavioral Changes: Behavioral changes have been reported, though the exact mechanisms are not fully understood.
Hair Loss: Some users have reported experiencing hair loss as a side effect.
Joint Pain and Stiffness: Like medically-approved aromatase inhibitors, unregulated versions can cause significant joint pain and stiffness (arthralgia).

Arimistane vs. Medically-Approved Aromatase Inhibitors


Feature	Arimistane (Androsta-3,5-diene-7,17-dione)	Medically-Approved AIs (e.g., Exemestane)
Regulatory Status	Not a legal dietary ingredient; classified as a banned synthetic steroid.	FDA-approved prescription drug.
Availability	Primarily through online supplement vendors, often deceptively labeled.	Requires a doctor's prescription and dispensing by a licensed pharmacist.
Uses	Marketed for bodybuilding, PCT, and increasing testosterone. Not scientifically supported and banned in sports.	Approved for treating hormone receptor-positive breast cancer in postmenopausal women.
Scientific Evidence	Lack of good scientific evidence to support its purported uses.	Extensively studied in clinical trials for approved medical conditions.
Oversight	No quality control or standardization. Often mislabeled.	Manufacturing, quality, and dosing are rigorously controlled and standardized.
Safety Profile	Associated with serious health risks including liver/kidney damage.	Documented side effects, but managed under medical supervision.

Conclusion: The Verdict on Arimistane

While marketed with promises of enhanced muscle growth and hormonal optimization for bodybuilders, arimistane is a dangerous and unregulated synthetic steroid. Its status as a banned substance by WADA and an illegal ingredient by the FDA should serve as a stark warning to anyone considering its use. The potential for severe and permanent health consequences, including liver and kidney damage, outweighs any speculative benefits. Medically-approved aromatase inhibitors exist for legitimate, supervised therapeutic uses, but arimistane is not among them. Consumers are strongly advised to avoid this substance and consult healthcare professionals for any concerns regarding hormonal health or athletic performance.

For further information on the FDA's stance, see the official FDA Warning Letter on Arimistane.

Frequently Asked Questions

In many countries, it is not approved as a dietary supplement ingredient, and it is explicitly banned in competitive sports by the World Anti-Doping Agency (WADA). The U.S. Food and Drug Administration (FDA) considers it an unapproved new drug and illegal to market as a supplement.

Reported side effects include potential liver and kidney damage, hair loss, joint pain, decreased bone density, and changes in mood. It can cause significant hormonal imbalances due to its potent estrogen-blocking effects.

Yes, the FDA classifies arimistane (Androsta-3,5-diene-7,17-dione) as a synthetic anabolic-androgenic steroid, not a dietary ingredient.

An aromatase inhibitor works by blocking the aromatase enzyme, which converts androgens (like testosterone) into estrogens. This action is intended to increase testosterone levels and decrease estrogen.

According to WebMD, there is not enough reliable information to determine safe and appropriate use, and it warns that the substance might be unsafe for most people when taken orally.

No, arimistane is on the WADA Prohibited List, and its use is banned for athletes in all competitive sports.

Medically-approved aromatase inhibitors (like anastrozole or exemestane) are regulated prescription drugs used for specific medical treatments, like breast cancer. Arimistane is an unregulated, unapproved, synthetic steroid with documented health risks and no scientifically validated uses.

In bodybuilding, arimistane was marketed for use during Post-Cycle Therapy (PCT) to help restore hormonal balance after a steroid cycle and as an estrogen blocker to achieve a 'harder' or more vascular physique. These uses are based on unsubstantiated claims and carry significant health risks.