What Should I Tell My Healthcare Provider?You should talk with your healthcare provider prior to taking letrozole if you have:
- Liver disease, including liver failure or cirrhosis
- Any allergies, including allergies to food, dyes, or preservatives.
Also, let your healthcare provider know if you are:
- Pregnant or thinking of becoming pregnant (see Femara and Pregnancy)
- Breastfeeding (see Femara and Breastfeeding)
A premenopausal woman.
You should also make sure to tell your healthcare provider about all of the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements.
(Click Precautions and Warnings With Letrozole to learn more, including information on who should not take the drug.)
How Does Letrozole Work?Letrozole is part of a group of medications called aromatase inhibitors. Aromatase is an enzyme found in various places in the body. These enzymes help produce estrogens (in particular, a certain estrogen called estradiol). In postmenopausal women, most of the estrogen in the body is made by aromatase. By blocking these enzymes, letrozole helps to decrease the amount of estrogen in the body.
Many breast cancers are sensitive to the estrogen hormone, meaning that the tumor grows with its help. When a tumor is sensitive to estrogen, it has receptors on the outer surface of its cells, into which estrogen fits like a key opening a lock. When this connection is made, the cancer grows. Breast cancers that have estrogen (and/or progesterone) receptors are known as hormone receptor-positive tumors.
By decreasing estrogen production, letrozole can help decrease the growth of these breast cancers. This type of breast cancer treatment is known as hormonal therapy (see Breast Cancer Hormone Treatment).