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What is Femara (letrozole) and what is it used for?

Medically reviewed by Last updated on May 22, 2023.

Official answer


Femara (letrozole) is a prescription medication used for the treatment of breast cancer, ovulation problems and unexplained infertility. Femara is the brand name that Novartis uses for its version of letrozole.

What is Femara (letrozole)?

Femara is an aromatase inhibitor and type of hormone (endocrine) therapy, which is available in the form of a tablet. Hormones are chemicals produced by our bodies that act as messengers and are part of an internal communication system. Hormones travel in our bloodstream and affect many different processes including growth, fertility, metabolism and more.

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. Estrogen is a hormone that causes some types of breast cancer to grow.

In women with fertility problems, blocking the action of aromatase and lowering levels of estrogen causes the body to increase production of follicle stimulating hormone (FSH), which can stimulate ovarian follicles leading to an egg or eggs being released during ovulation.

What is Femara (letrozole) used for?

Femara is approved by the US Food and Drug Administration (FDA) in postmenopausal women as:

  • An adjuvant treatment for hormone receptor positive early breast cancer.
  • An extended adjuvant treatment for early breast cancer who have previously been treated with standard adjuvant tamoxifen therapy.
  • A first- and second-line treatment for hormone receptor positive or unknown advanced breast cancer.

Femara is also used off-label (without FDA approval) as a fertility treatment. It is used for:

  • Ovulation induction. Femara induces ovulation in patients with polycystic ovary syndrome (PCOS), which is a condition where hormone imbalance can interfere with ovulation leading to anovulation (a lack of ovulation).
  • Increasing the chances of pregnancy in women who ovulate. Femara is also used to increase the chance of pregnancy in women who already ovulate. In these women, treatment with Femara can result in the development of multiple follicles leading to multiple eggs being released. This process is known as controlled ovarian hyperstimulation or superovulation.

In June 2018, the American College of Obstetricians and Gynecologists (ACOG) updated its treatment guidelines to recommend Femara as a first-line treatment for the induction of ovulation in all women with PCOS, not just those with PCOS and a BMI (body mass index) of greater than 30 as was previously the case.

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