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Aromasin - Exemestane

Aromasin protects against estrogen-related side effects. It is mild Aromatase Inhibitor used to prevent gyno during highly androgenic steroid cycles.

Aromasin Description

Aromasin (exemestane) is a steroidal suicide aromatase inhibitor. It is very similar in structure and action to formestane, although it is significantly more potent in comparison. As a class of drugs, aromatase inhibitors offer an anti-estrogenic effect by blocking the enzyme responsible for synthesizing estrogens. Aromasin is approved by the FDA for the treatment of breast cancer in women, specifically in post-menopausal patients whose cancer has progressed following therapy with tamoxifen. Male bodybuilders and athletes often use the drug for non-approved purposes, namely to counter the estrogenic side effects associated with the use of aromatizable anabolic/androgenic steroids. This may include gynecomastia, fat buildup, and water retention. In some instances aromatase inhibitors may also assist this group with the loss of body fat and increases in muscular definition. Exemestane is one of the most potent aromatase inhibitors presently available. The most commonly cited data (found in the Aromasin packaging insert) reports a lowering of serum estrogen levels by 85% on average in clinical studies with women.


Exemestane was developed by Pharmacia & Upjohn (Pharmacia), which gained FDA approval for the sale of the drug in late 1999. They introduced it under the Aromasin brand name in early 2000. Although the drug proved to be effective in doses as low as 2.5 mg per day in some patients, the company developed it in a standard and near-universally effective dosage of 25 mg per tablet¹. The company has since introduced the drug to many other nations under the same trade name. Due to various patents and general market dominance, Aromasin is the only pharmaceutical brand name of exemestane one is likely to come across in general commerce at the present time. It is currently available in over three dozen countries including Argentina, Australia, Austria, Belgium, Brazil, Canada, Czech Republic, Chile, Denmark, Finland, France, Germany, Greece, Hong Kong, Hungary, Ireland, Israel, Italy, Malaysia, Netherlands, Norway, New Zealand, Philippines, Poland, Portugal, Russia, South Africa, Singapore, Spain, Sweden, Switzerland, Thailand, Turkey, United Kingdom, United States, and Venezuela.

How Supplied

Aromasin (exemestane) is most commonly supplied in tablets of 25 mg.

Structural Characteristics

Exemestane is classified as an irreversible steroidal aromatase inhibitor. It has the chemical designation 6-methyl-enandrosta-1,4-diene-3,17-dione.

Side Effects

Common side effects associated with the use of an aromatase inhibitor like Aromasin include hot flashes, joint pain, weakness, fatigue, mood changes, depression, high blood pressure, swelling of the arms/legs, and headache. Aromatase inhibitors may also decrease bone mineral density, which may lead to osteoporosis and an increase in fractures in susceptible patients. Some individuals may also respond to the medication with gastrointestinal side effects including nausea and vomiting. Aromatase inhibitors can harm the development of an unborn fetus, and should never be taken or handled during pregnancy.

When taken by men (as an off-label use) to reduce estrogenicity during prolonged periods of steroid treatment, aromatase inhibitors may increase cardiovascular disease (CVD) risk by retarding some beneficial properties of estrogen on cholesterol values. Studies have demonstrated that when an aromatizable steroid such as testosterone enanthate is taken in conjunction with an aromatase inhibitor, suppression of HDL (good) cholesterol levels become significantly more pronounced. Since the estrogen receptor agonist/antagonist Nolvadex® generally does not display the same anti-estrogenic (negative) effect on cholesterol values, it is usually favored over aromatase inhibitors for estrogen maintenance by male bodybuilders and athletes concerned with cardiovascular health.


Aromasin (exemestane) is FDA approved for the adjunctive treatment of postmenopausal women with estrogen-receptor-positive early breast cancer with disease progression following tamoxifen. Therapy is initiated 2-3 years after tamoxifen has failed to elicit a desirable response, at which point tamoxifen is discontinued. Treatment with exemestane is continued for 2-3 additional years, and is completed after 5 years of cumulative adjunctive drug therapy (tamoxifen and exemestane treatment combined). The dosage prescribed in all instances is one 25 mg tablet per day, taken after a meal. When used to mitigate the estrogenic side effects of anabolic/androgenic steroid use or increase muscle definition, male athletes and bodybuilders will commonly take 12.5 mg to 25 mg of exemestane per day. In some instances, a half of a tablet (12.5 mg) taken every other day is sufficient to prevent the onset of estrogenic side effects.


Exemestane is available in the U.S and in more than three dozen other nations under the Aromasin brand name (Pharmacia). Aromasin, likewise, dominates the global market and is presently the primary exemestane product one is likely to encounter.



  1. Endocrinological and clinical evaluation of exemestane, a new steroidal aromatase inhibitor. N. Zilembo, C. Noberasco et al. Br J Cancer. 1995 Oct; 72(4): 1007–1012.