Letrozole 2.5 mg is indicated for the treatment of hormone receptor-positive breast cancer in postmenopausal women, contraindicated in patients with known hypersensitivity to letrozole or any of its excipients, common side effects include hot flashes, joint pain, and fatigue, and it may interact with drugs that affect estrogen levels or are metabolized by CYP2A6 and CYP3A4 enzymes.