Arimidex is considered an estrogen blocker because it decreases the amount of the hormone estrogen in your body. It isn’t a steroid drug or a type of chemotherapy (traditional drugs used to treat cancer).
Arimidex belongs to a class of drugs called aromatase inhibitors. It works by blocking an enzyme (a type of protein) called aromatase. This enzyme works to change hormones into estrogen.
By blocking this change, Arimidex decreases the amount of estrogen in your body. This decreases the growth of breast cancer.
In studies, Arimidex lowered levels of estradiol (a form of estrogen) by about 70% within 24 hours. After 14 days of treatment, estradiol levels were lowered by about 80%. And estradiol levels continued to be reduced for 6 days after stopping treatment.