A natural aromatase inhibitor can go by a variety of names. The direct estrogen blocker is called fulvestrant, or Faslodex. Indirect inhibitors go by the names anastrozole, exemestane and letrozole. Respectively, these have the brand names Arimidex, Aromasin and Femara. All are typically taken once a day in pill form.
Another type of hormone therapy drug called tamoxifen is often used in concert with a natural aromatase inhibitor. These are not taken together, but rather in alternating periods. According to the Breast Cancer Diagnosis Guide, doctors often start with a natural aromatase inhibitor since it has slightly fewer side effects. Many physicians also alternate each treatment every two or three years.