Letrozole

What it is and how it works

Mechanism of Action The growth of some cancers of the breast is stimulated or maintained by estrogens. Treatment of breast cancer thought to be hormonally responsive (i.e., estrogen and/or progesterone receptor positive or receptor unknown) has included a variety of efforts to decrease estrogen levels (ovariectomy, adrenalectomy, hypophysectomy) or inhibit estrogen effects (antiestrogens and progestational agents). These interventions lead to decreased tumor mass or delayed progression of tumor growth in some women.

Mechanism class: Aromatase Inhibitors

Indications

Letrozole Tablets, USP are aromatase inhibitor indicated for: Adjuvant treatment of postmenopausal women with hormone receptor positive early breast cancer Extended adjuvant treatment of postmenopausal women with early breast cancer who have received prior standard adjuvant tamoxifen therapy First and second-line treatment of postmenopausal women with hormone receptor positive or unknown advanced breast cancer Adjuvant Treatment of Early Breast Cancer Letrozole Tablets, USP are indicated for the adjuvant treatment of postmenopausal women with hormone receptor positive early breast cancer. Extended Adjuvant Treatment of Early Breast Cancer Letrozole Tablets, USP are indicated for the extended adjuvant treatment of early breast cancer in postmenopausal women, who have received 5 years of adjuvant tamoxifen therapy. The effectiveness of letrozole in extended adjuvant treatment of early breast cancer is based on an analysis of disease-free survival in patients treated with letrozole for a median of 60 months [ see Clinical Studies ( 14.2 , 14.3 ) ].

Dosage and administration (summary)

Letrozole tablets are taken orally without regard to meals : Recommended dose: 2.5 mg once daily Patients with cirrhosis or severe hepatic impairment: 2.5 mg every other day ( 2.5 , 5.3 ) Recommended Dose The recommended dose of Letrozole tablets is one 2.5 mg tablet administered once a day, without regard to meals. Use in Adjuvant Treatment of Early Breast Cancer In the adjuvant setting, the optimal duration of treatment with letrozole is unknown. In both the adjuvant study and the post approval adjuvant study, median treatment duration was 5 years.

Contraindications

● Pregnancy: Letrozole can cause fetal harm . ● Known hypersensitivity to the active substance, or to any of the excipients . Pregnancy Known hypersensitivity to the active substance, or to any of the excipients

Warnings and precautions

Decreases in bone mineral density may occur. Consider bone mineral density monitoring Increases in total cholesterol may occur. Consider cholesterol monitoring. Fatigue, dizziness and somnolence may occur. Exercise caution when operating machinery Embryo-Fetal toxicity: Can cause fetal harm when administered to pregnant women. Obtain a pregnancy test in females of reproductive potential. Advise females of reproductive potential to use effective contraception ( 5.6 , 8.1 , 8.3 ) Bone Effects Use of letrozole may cause decreases in bone mineral density (BMD).

Pregnancy

Pregnancy Risk S ummary Based on post-marketing reports, findings from animal studies and the mechanism of action, letrozole can cause fetal harm and is contraindicated for use in pregnant women. In post-marketing reports, use of letrozole during pregnancy resulted in cases of spontaneous abortions and congenital birth defects.

Storage and supply

Packaged in HDPE bottles with a safety screw cap. Letrozole Tablets, USP 2.5 mg Bottles of 30 tablets...................................................................................NDC 24979-726-06 Bottles of 90 tablets...................................................................................NDC 24979-726-07 Store at 20°C to 25°C (68°F …

Source: Letrozole Tablets (Letrozole) — US FDA prescribing information, 2026-03-19, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.