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Letrozole

Generic name: letrozole [ LET-roe-zol ]
Brand name: Femara
Dosage form: oral tablet (2.5 mg)
Drug classes: Aromatase inhibitors, Hormones / antineoplastics

Medically reviewed by Drugs.com on May 6, 2024. Written by Cerner Multum.

What is letrozole?

Letrozole lowers estrogen levels in postmenopausal women, which may slow the growth of certain types of breast tumors that need estrogen to grow in the body.

Letrozole is used to treat breast cancer in postmenopausal women. It is often given to women who have been taking tamoxifen (Nolvadex, Soltamox) for 5 years.

Letrozole may also be used for purposes not listed in this medication guide.

Letrozole side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Common side effects of letrozole may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Letrozole side effects (more detail)

Warnings

You should not use letrozole if you are pregnant.

Before taking this medicine

You should not use letrozole if you are allergic to it.

letrozole is for use only in women who can no longer get pregnant. Letrozole can harm an unborn baby. Do not use if you are pregnant. Use effective birth control if you are not past menopause. Keep using birth control for at least 3 weeks after your last dose of letrozole. Tell your doctor if you think you may be pregnant.

Tell your doctor if you have ever had:

You should not breastfeed while you are using letrozole and for at least 3 weeks after your last dose.

How should I take letrozole?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

You may take letrozole with or without food.

You will need frequent medical tests, and your bone mineral density may also need to be checked.

Store at room temperature away from moisture and heat.

Letrozole dosing information

Usual Adult Dose for Breast Cancer:

2.5 mg orally once a day

Duration of therapy:
-Adjuvant and extended adjuvant settings: Optimal duration is unknown; discontinue therapy at relapse.
-Advanced disease: Until tumor progression is evident.

Uses:
-Adjuvant treatment of postmenopausal women with hormone receptor positive early breast cancer
-Extended adjuvant treatment of early breast cancer in postmenopausal women who have received 5 years of adjuvant tamoxifen therapy
-First-line treatment of advanced breast cancer in postmenopausal women with hormone receptor positive or unknown locally advanced or metastatic breast cancer; second-line treatment of advanced breast cancer in postmenopausal women with disease progression following antiestrogen therapy

Usual Adult Dose for Breast Cancer -- Adjuvant:

2.5 mg orally once a day

Duration of therapy:
-Adjuvant and extended adjuvant settings: Optimal duration is unknown; discontinue therapy at relapse.
-Advanced disease: Until tumor progression is evident.

Uses:
-Adjuvant treatment of postmenopausal women with hormone receptor positive early breast cancer
-Extended adjuvant treatment of early breast cancer in postmenopausal women who have received 5 years of adjuvant tamoxifen therapy
-First-line treatment of advanced breast cancer in postmenopausal women with hormone receptor positive or unknown locally advanced or metastatic breast cancer; second-line treatment of advanced breast cancer in postmenopausal women with disease progression following antiestrogen therapy

Detailed Letrozole dosage information

Kisqali, Verzenio, Trodelvy, Keytruda, tamoxifen, Arimidex, Femara, paclitaxel, Xeloda, Taxol

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking letrozole?

Avoid driving or hazardous activity until you know how letrozole will affect you. Your reactions could be impaired.

What other drugs will affect letrozole?

Other drugs may affect letrozole, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Letrozole drug interactions (more detail)

Does letrozole interact with my other drugs?

Enter medications to view a detailed interaction report using our Drug Interaction Checker.

Popular FAQ

How long do letrozole side effects last?

Most side effects of letrozole are mild and temporary, lasting only a few days or weeks until your body gets used to taking the medication. Some other side effects of letrozole take a few months to develop and tend to persist long term until you stop taking letrozole. The half-life of letrozole is 2 days, so once you stop taking letrozole, you might continue to experience side effects for about a week to 10 days after your last dose. Continue reading

What happens when you stop taking letrozole?

When you stop taking letrozole, side effects such as swelling, cough, hot flashes, and nausea, should improve within a week or 10 days. Some, such as high cholesterol, bone loss, and hair thinning may take many months to resolve. As long as you have taken it for at least 5 years, then letrozole should continue to reduce the risk of breast cancer coming back for many years after you stop taking it. Letrozole is usually taken for 5 years, but may be recommended for up to 10 years depending on individual circumstances. Continue reading

When is the best time of day to take letrozole?

You can take letrozole (Femara) in the morning or evening, but you should take it at about the same time each day. Taking it at the same time each day will help you to remember your dose. Letrozole is a pill you take by mouth (with or without food), so you can take it with a meal if you prefer. If you miss a dose, do not double your dose the next day. Continue reading

Is letrozole a form of chemotherapy?

Letrozole is not chemotherapy, it is a type of hormone therapy that is used to treat people with breast cancer that is hormone receptor-positive. If your cancer is hormone receptor-negative, then letrozole will not be of any benefit. Traditional chemotherapy agents stop cancer cells from growing, dividing, and making more cells. Letrozole works by blocking the action of the enzyme aromatase, which prevents the body from converting androgens into estrogens. Estrogen is a hormone that causes estrogen receptor-positive (ER+) breast cancer to grow. Letrozole belongs to the class of medicines known as aromatase inhibitors. Continue reading

Does letrozole affect blood sugar levels?

Although diabetes and blood sugar increases are not listed as a side effect of letrozole treatment, treatment with letrozole is associated with a significantly increased risk for high blood sugar levels and diabetes. An Israeli study that investigated 2,246 breast cancer survivors found that women treated with letrozole were 4.3 times more likely to develop diabetes than women not taking letrozole, although the number of women prescribed letrozole was small. Overall, women prescribed any sort of hormone treatment (either tamoxifen or an aromatase inhibitor such as letrozole) had a 2.5 times higher risk of diabetes. Continue reading

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Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer

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