Femara is a medication that is used for the treatment of some types of breast cancer in postmenopausal women. It belongs to the class of drugs called aromatase inhibitors  and letrozole is its active ingredient. It is a hormone therapy drug, not a chemotherapy drug.
Femara is used to treat some types of breast cancer in women who have gone through the stage of menopause. Breast cancer arises when there is an abnormal growth of breast cells. It is used in the treatment of the following kinds of breast cancer:
- Hormone receptor positive (HR+) breast cancer: The female sex hormones, estrogen  and progesterone  are substances that enable the growth of this type of breast cancer. The cancerous cells have receptors that bind to these hormones which stimulate them to grow and multiply. Femara works by inhibiting the production of these hormones thereby preventing the growth of cancer.
- Early breast cancer: In this type, the breast cancer is still localized in the breast or in the lymph nodes of your armpit.
- Advanced breast cancer: In this type, cancer has spread past the lymph nodes of your armpit to other regions of the body.
Sometimes, Femara is also used to treat infertility problems in females especially when it is caused by problems with ovulation.
Mechanism of Action
Femara helps reduce the level of estrogen in females. This hormone is known for aiding the growth of breast cancers. In women who have gone through menopause, their ovaries no longer produce estrogen. But with the aid of aromatase, an enzyme, androgens  are mostly converted to estrogen in other parts of the body. Femara, which is an aromatase inhibitor, prevents the action of aromatase so that it no longer converts androgens to estrogen which is useful for the growth of breast cancers. This action stops or greatly decelerates the growth of breast cancers.