drugs that lower estrogen levels by blocking the enzyme (aromatase) that converts androgens into estrogen. These drugs are used to treat hormone-sensitive breast cancer in women after menopause. Examples include anastrozole (Arimidex®), letrozole (Femara®), and exemestane (Aromasin®). These drugs are also being tested to see if they can reduce breast cancer risk in women after menopause. See also chemoprevention, estrogen, hormone therapy, menopause.