Femara (Letrozole) is a medication used to treat certain types of breast cancer in women after menopause. It is an aromatase inhibitor, which works to reduce the amount of estrogen in the body. Each tablet contains 2.5mg of letrozole, and this package contains 30 tablets. Femara is usually used for 5 years or until the cancer progresses. It can also be used in combination with other medications as part of a treatment plan. Common side effects may include hot flashes, fatigue, joint pain, and headache.