LETROZOLE

PRODUCT IDENTIFICATION

H.S. CODE

TOXICITY

CLASSIFICATION

Aromatase inhibitors

PHYSICAL AND CHEMICAL PROPERTIES

AUTOIGNITION

NFPA RATINGS

REFRACTIVE INDEX

Stable under ordinary conditions.

GENERAL DESCRIPTION & APPLICATIONS

Letrozole is a reversible (Type II), nonsteroidal aromatase inhibitor. Aromatase catalyzes the final and rate-limiting step in the conversion of androgens to estrogens in peripheral tissues. This occurs mainly in adipose tissue, but also in normal and malignant breast tissues, and provides the main source of estrogen in postmenopausal women. The goal of hormone therapy in breast cancer is to deprive tumour cells of estrogens, which are implicated in the development or progression of tumours. Maximal estrogen suppression is produced by a 0.1 mg dose, although a higher dose (ie, 2.5 mg per day) was associated with increased clinical responses. Maximal estrogen suppression occurs 48-78 hours after a single dose.6 Highly selective blockade of aromatase does not interfere with the production of other steroids (eg, adrenal corticosteroids, aldosterone) or thyroid stimulating hormone.5 Letrozole does not have progestogenic, androgenic or estrogenic activity. Differences in the mechanism of action may contribute to the apparent lack of cross-resistance between steroidal (eg, exemestane) and nonsteroidal (eg, anastrozole, letrozole) aromatase inhibitors.(http://www.bccancer.bc.ca/)

Aromatase inhibitors lower the amount of estrogen in post-menopausal women who have hormone-receptor-positive breast cancer. The hormone estrogen delivers growth signals to the hormone receptors. With less estrogen in the body, the hormone receptors receive fewer growth signals, and cancer growth can be slowed down or stopped. Before menopause, the ovaries produce most of a woman's estrogen, so reducing estrogen from other sources has little or no effect. But in post-menopausal women, most of the body's estrogen is made from another hormone, androgen. Aromatase inhibitors stop the enzyme called aromatase from turning androgen into estrogen, lowering the amount of estrogen produced OUTSIDE the ovaries. That means less estrogen in the bloodstream, less estrogen reaching estrogen receptors, and less cancer cell growth (http://www.breastcancer.org/)

Pharmacological actions:

• Antineoplastic agent
• Aromatase Inhibitor

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