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What is Letrozole?

By Jacquelyn Gilchrist
Updated May 17, 2024
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Letrozole is a drug that may be used to treat breast cancer. This medication is a type of drug called a nonsteroidal aromatase inhibitor. It is taken by mouth in the form of a tablet. In the United States, it is available by prescription only and is commonly sold under the brand name Femara®.

Some types of breast cancers respond to estrogen. This hormone can increase the growth of these tumors. Letrozole works by decreasing the amount of estrogen that the body produces. This may help to discourage the growth of malignant lesions.

Letrozole is intended for use only by women who are no longer of childbearing age. Possible candidates must have already ceased to menstruate. It is often used in patients who have already undergone other cancer treatments, such as radiation, chemotherapy, and used other cancer drugs, like tamoxifen. This nonsteroidal aromatase inhibitor may help prevent any remaining cancer cells from spreading.

Patients taking letrozole should follow dosage instructions carefully. The drug is typically taken once daily. It should be taken at about the same time each day. Patients may need to take it for several years, and should continue to take the drug even if they feel healthy.

Letrozole may cause some side effects. Patients should keep a record of any changes they experience and consult with their doctor. Some possible side effects include nausea, vomiting, and dizziness, as well as night sweats and extreme fatigue. The drug can also cause insomnia, swelling of the extremities and lower legs, and joint, bone, or muscle pain. Vaginal irritation or bleeding may also occur.

Some patients may also experience chest pains or problems breathing properly. If these occur, the patient should contact her doctor immediately. Other side effects that may require immediate attention include sudden numbness, vision changes, and slurred speech. Rarely, it may contribute to a heart attack, bone fracture, and breast pain, as well as flu-like symptoms.

Regular doctor visits are necessary for patients taking letrozole. The physician will need to verify that the drug is working, and is not causing undesirable side effects. A bone density screening may also be appropriate for women with osteoporosis, or those who are at risk for the disease, as this drug can cause a loss of bone density, or it may worsen the condition.

Before taking letrozole, patients should discuss other medications they are taking with their doctors. Other medical conditions should also be disclosed. For example, women with liver disease or high cholesterol may be unable to use this drug.

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Discussion Comments
By literally45 — On Aug 04, 2013

Who else is on letrozole for breast cancer? Are you experiencing side effects?

I've been on letrozole for almost a year now and I'm experiencing so many side effects. I have hair thinning and sometimes I get dizzy spells and chronic fatigue.

I am on hormonal therapy for breast cancer and I'm taking two other drugs in addition to letrozole, so I might be mixing side effects. I am sure however that the hair loss and thinning is due to letrozole because these side effects started soon after I started treatment with it.

Is anyone else experiencing this?

By ZipLine — On Aug 04, 2013

@feruze-- Yes, letrozole is used as hormonal therapy for breast cancer in women, as well as for male gynecomastia. This is an estrogen antagonist, so it prevents tumor growth and can reduce breast tissue growth in men. It's a common treatment, you are definitely not the only person using it for this reason.

By the way, has it been working for you? I heard that letrozole can be a hit or miss for gynecomastia.

By bear78 — On Aug 03, 2013

My doctor prescribed letrozole for my gynecomastia. Is this a common treatment? I had no idea that letrozole is used by women for breast cancer.

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