LETROZOLE TABLETS

12.1 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. In postmenopausal women, estrogens are mainly derived from the action of the aromatase enzyme, which converts adrenal androgens (primarily androstenedione and testosterone) to estrone and estradiol. The suppression of estrogen biosynthesis in peripheral tissues and in the cancer tissue itself can therefore be achieved by specifically inhibiting the aromatase enzyme. Letrozole is a nonsteroidal competitive inhibitor of the aromatase enzyme system; it inhibits the conver

Contraindications

• • 4 CONTRAINDICATIONS ● Pregnancy: Letrozole can cause fetal harm [see Use in Specific Populations (8.1) ] . ● Known hypersensitivity to the active substance
• • or to any of the excipients [see Adverse Reactions (6) ] . Pregnancy ( 4 ) Known hypersensitivity to the active substance
• • or to any of the excipients ( 4 )