Arimidex is not currently approved for bodybuilding purposes. It’s only approved to treat certain forms of breast cancer.
Arimidex is sometimes taken to lower estrogen levels that are high due to anabolic steroid use. High estrogen levels can cause side effects such as gynecomastia (unusual breast gland enlargement). Some people use Arimidex to help reduce such side effects.
Using Arimidex this way is not recommended, and may not be safe. You should not take Arimidex or other drugs unless they’re prescribed for you. In fact, the World Anti-Doping Agency lists aromatase inhibitor drugs as banned substances. Arimidex is a type of aromatase inhibitor.
It’s not known what side effects Arimidex may cause if taken for bodybuilding or whether the drug could lead to more serious problems if used this way. Its dosage for this use also isn’t known, such as the dosage if taken during steroid cycles.
See this article for details about Arimidex and bodybuilding. You might also have questions such as how much Arimidex would be taken with 200 mg of testosterone, or the differences between Arimidex versus Aromasin. Your doctor can help answer such questions and determine whether Arimidex is safe for you.