exemestane

Exemestane is a selective, steroidal aromatase inhibitor used in the treatment of hormone receptor–positive breast cancer in postmenopausal women. It acts as a mechanism-based irreversible inhibitor of aromatase (CYP19A1), the enzyme that converts androgens to estrogens in peripheral tissues. By inactivating aromatase, exemestane lowers systemic estrogen levels, reducing the growth stimulus for estrogen-dependent tumors.

Indications for exemestane include metastatic breast cancer in postmenopausal women with estrogen receptor–positive disease and adjuvant therapy for early-stage hormone receptor–positive breast cancer after 2 to 3 years of tamoxifen, particularly in switching therapy. It is administered orally at a dose of 25 mg once daily and continued until disease progression or intolerance. Exemestane is not effective in premenopausal women unless ovarian estrogen production is suppressed.

Common adverse effects include hot flashes, fatigue, arthralgia and joint stiffness, and an increased risk of osteoporosis with fractures. Other possible effects include nausea, sweating, sleep disturbances, and rare hepatotoxicity. Safety considerations include avoiding use during pregnancy and lactation. Drug interactions may occur with therapies that affect hepatic enzymes or estrogen pathways, and long-term use warrants monitoring of bone density and lipid profiles. Exemestane is one option among endocrine therapies for postmenopausal patients with hormone receptor–positive breast cancer.