Femara lowers estrogen levels and is used to treat breast cancer in postmenopausal women. Learn about side effects, interactions and indications. Find patient medical information for Letrozole (Femara) on WebMD including its uses, side effects and safety, interactions, pictures, warnings, and user ratings “I’m on my third year of Femara and am tolerating it well. I categorize my side effects as ‘inconsistent and somewhat annoying.’ For example; I have sporadic instances of calf and arch cramps; intense sweating, joint pain and stiffness — but never all at once and not day after day. Femara (letrozole) is a brand-name prescription drug used for certain types of breast cancer. Learn about side effects, off-label use for infertility, and more. Learn about letrozole (Femara) usage and dosing. Read the latest news and reviews about the drug as well as potential side effects and popular alternatives. Downloadable Content Prescribing information (PDF 613.13 KB) Hormone therapies, such as Femara, are used to treat patients with cancers that are fueled by hormones. Femara works by blocking the action of the enzyme aromatase, which prevents the body from converting androgens into estrogens. Learn about side effects, cost, uses, and more of Femara (letrozole), which is a prescription drug that treats breast cancer in certain females. Drug Summary What Is Femara? Femara (letrozole) is a non-steroidal aromatase inhibitor (lowers estrogen production) used to treat breast cancer in postmenopausal women. Femara is often given to women who have been taking tamoxifen (Nolvadex, Soltamox) for 5 years. Femara is available in generic form. What Are Side Effects of Femara? Letrozole, sold under the brand name Femara among others, is an aromatase inhibitor medication that is used in the treatment of breast cancer for post-menopausal women.