Since Arimidex was introduced, many bodybuilders simply ignored it despite its amazing antiestrogenic effects, due to its price- people were paying 250$ for 28 tabs just ten years ago. These days, with cheaper generics and UG versions of the drug, it deserves a second look.
In contrast to Nolvadex, Arimidex does not block estrogen receptors but rather prevents testosterone and other steroids from turning into estrogen. This results in more 'quality' gains during a cycle and doses as low as .5mg eod are enough to significantly reduce most bloating and gynocomastia with moderate cycles.
Most studies also show that taking several mgs of Arimidex per day is not significantly more effective than merely taking 1mg eod- so its effects are quite dramatic at even low doses.