Letrozole

Letrozole is a prescription medication used to treat breast cancer in women who have already gone through menopause. Letrozole belongs to a group of drugs called aromatase inhibitors. These work by decreasing the amount of estrogen produced by the body, which can slow and/or stop the growth of some types of breast cancer cells that require estrogen to grow.

This medication comes in tablet form and is usually taken once daily, with or without food.

Common side effects of letrozole include joint pain, hot flashes, and night sweats.

Letrozole may also cause dizziness and/or blurred vision. Do not drive or operate heavy machinery until you know how letrozole affects you.

Breast cancer is cancer that forms in the cells of the breasts. The development of breast cancer is strongly related to the amount of estrogen the breast is exposed to over time. Some women have hormone receptor positive (ER/PR+) breast cancer. Estrogen receptors are proteins found on the surface of cells. Cancer cells grow in response to estrogen binding to these receptors. Letrozole lowers the amount of estrogen in the blood, limiting the amount of estrogen available to bind to these receptors. This slows or stops the growth of cancer cells. 

Hormone receptor testing is done to determine how likely it is that letrozole will be an effective treatment. Patients who do not have hormone receptor positive breast cancer are not likely to respond to treatment with letrozole.

Letrozole is a prescription medication used to treat postmenopausal women who:

• have hormone receptor-positive early-stage breast cancer and have had other treatments, such as radiation or surgery to remove a tumor
• have already been treated with a medication called tamoxifen for 5 years
• have untreated breast cancer that has spread within the breast or to other areas of the body and women whose breast cancer has worsened while they were taking tamoxifen

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.

Letrozole may be found in some form under the following brand names:

• Femara

Serious side effects have been reported with letrozole. See the "Letrozole Precautions" section.

Common side effects of letrozole include:

• hot flashes
• night sweats
• nausea
• vomiting
• loss of appetite
• constipation
• diarrhea
• heartburn
• back pain
• stomach pain
• changes in weight
• muscle, joint, or bone pain or arthritis
• fatigue
• headache
• high cholesterol
• dizziness
• drowsiness
• weakness
• swelling of the hands, feet, ankles, or lower legs
• difficulty falling asleep or staying asleep
• vaginal bleeding or irritation
• breast pain
• hair loss
• blurry vision

This is not a complete list of letrozole side effects. Ask your doctor or pharmacist for more information.

Tell your doctor if you have any side effect that bothers you or that does not go away.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements. Especially tell your doctor if you take:

• hormonal contraceptives (birth control pills, implants, patches, rings, and/or injections)
• hormone replacement therapy (HRT) medications
• raloxifene (Evista)
• tamoxifen (Nolvadex)

This is not a complete list of letrozole drug interactions. Ask your doctor or pharmacist for more information.

Serious side effects have been reported with letrozole including:

• decreased bone mineral density. Letrozole and other medications that lower the amount of estrogen in the body can lead to osteoporosis. Talk to your doctor about this if you are a woman over the age of 55 or already have osteoporosis.
• increased blood levels of letrozole in patients with liver disease. Patients with severe liver disease or cirrhosis may require a dose reduction.
• increased blood cholesterol levels. Your doctor may monitor your blood cholesterol levels and cholesterol-lowering medications may be required.

Do not take letrozole if you:

• are allergic to any ingredient in letrozole
• have not gone through menopause. This medication is not intended for women who have not gone through menopause
• are pregnant

Letrozole may also cause dizziness and/or blurred vision. Do not drive or operate heavy machinery until you know how letrozole affects you.

Medications can interact with certain foods. In some cases, this may be harmful and your doctor may advise you to avoid certain foods. In the case of letrozole, there are no specific foods that you must exclude from your diet when receiving this medication.

Before receiving letrozole, tell your doctor about all of your medical conditions. Especially tell your doctor if you:

• are allergic to any ingredient in letrozole
• have high cholesterol
• have osteoporosis
• have liver disease
• have not gone through menopause
• are pregnant or breastfeeding

Tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements.

Tell your doctor if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

Letrozole falls into category X. It has been shown that letrozole may harm the unborn baby. There are no situations where the benefits of the medication for the mother outweigh the risks of harm to the baby. These medicines should never be used by pregnant women.

Tell your doctor if you are breastfeeding or plan to breastfeed.

It is not known if letrozole crosses into human milk. Because many medications can cross into human milk and because of the possibility for serious adverse reactions in nursing infants with use of this medication, a choice should be made whether to stop nursing or stop the use of this medication. Your doctor and you will decide if the benefits outweigh the risk of using letrozole.

Take letrozole exactly as prescribed. 

Letrozole comes in tablet form and is taken once daily, with or without food.

If this medication upsets your stomach, try taking it with food and try to take letrozole at the same time each day.

If you miss a dose, take the missed dose as soon as you remember. If it is almost time for the next dose, skip the missed dose and take your next dose at the regular time. Do not take two doses of letrozole at the same time.

Take this medication exactly as prescribed by your doctor. Follow the directions on your prescription label carefully.

The dose your doctor recommends may be based on the following:

• the condition being treated
• other medical conditions you have
• other medications you are taking or have taken in the past
• how you respond to this medication
• liver function
• your weight
• your age

The recommended dose of letrozole is 2.5 mg taken by mouth once daily.

If you take too much letrozole, call your healthcare provider or local Poison Control Center, or seek emergency medical attention right away.

Store at room temperature between 15 and 30°C (59-86°F).

Keep this and all medications out of the reach of children.