How Femara Works
To understand how Femara® (letrozole) 2.5 mg tablets works, you must first be familiar with the relationship between estrogen and hormone receptor-positive early breast cancer.
Hormone-dependent breast cancers contain protein molecules called estrogen receptors. When no estrogen is present, the estrogen receptors remain inactive. However, when estrogen receptors are exposed to estrogen they trigger a chain of events that can cause tumor cell growth and multiplication. This is shown in illustration A.
Tumors that contain these estrogen receptors are known as estrogen receptor-positive (ER+) tumors or estrogen dependent and can be treated with hormone therapy. A laboratory test determines whether breast cancer is estrogen receptor-negative (ER-) or ER+. A tumor must have been diagnosed as ER+ or ER-unknown for Femara to be prescribed. This is shown in illustration B.
Femara is a form of hormone therapy known as an aromatase inhibitor, which works by reducing the amount of estrogen produced in the bodies of postmenopausal women. While tamoxifen prevents estrogen from being used as fuel to help the cancer grow, Femara seeks to prevent cancer cells from developing by starving them of estrogen, thus denying them the chance to grow or spread.
Surgery, radiation, and chemotherapy are used to remove hormone receptor-positive early breast cancer cells from the body. Even if a woman has undergone one or all three forms of treatment, a small number of breast cancer cells may remain. Illustrations C and D below show how Femara interferes with the production of estrogen triggered by aromatase.
Before therapy: Androgen (a hormone found in both men and women) is produced by fat, muscle, and adrenal glands. The aromatase enzyme is needed to convert androgen into estrogen, which results in tumor growth.
With therapy: Femara binds to the aromatase enzyme and blocks it from converting androgen to estrogen, thereby helping to reduce tumor growth.
Remember to take your medicine as prescribed by your doctor.
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Indication Important Safety Information Femara is only indicated in postmenopausal women. You should not take Femara if you are premenopausal. Your doctor should discuss the need for adequate birth control if you have the potential to become pregnant, if you are not sure of your postmenopausal status, or if you recently became postmenopausal. You should not take Femara if you are pregnant as it may cause harm to an unborn child. You should also discuss with your doctor what to do if you are nursing a child. The use of Femara may cause decreases in the density of your bones, increases in bone fractures and osteoporosis. Monitoring of the density of your bones may be required. Some patients taking Femara had an increase in cholesterol. Your doctor may require the monitoring of cholesterol in your blood. Some women reported fatigue, dizziness and drowsiness with Femara. Until you know how it affects you, use caution before driving or operating machinery. Some women had moderate, temporary decreases in white blood cell counts. The medical significance of this is not known. The most serious side effects seen with Femara are bone effects (fractures, decreased bone density and osteoporosis) and increases in cholesterol. Other common side effects seen with Femara include joint pain, nausea, weight decrease, vaginal irritiation, and pain in the extremitites. Other important less commonly reported side effects include blood clots, other cancers, stroke, heart attack and endometrial cancer. Femara is a once-daily, convenient prescription tablet. Your doctor may tell you to take Femara every other day if you have severe liver disease. Always take your medicine exactly as prescribed by your doctor. For full prescribing information, please click here. You are encouraged to report negative side effects of prescription drugs to the FDA. Visit www.fda.gov/medwatch or call 
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