Letrozole (By mouth)

Letrozole (LET-roe-zole)

Treats breast cancer.

Brand Name(s):

Femara, Letrozole AvPak

There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

This medicine is not right for everyone. Do not use it if you had an allergic reaction to letrozole, or if you are pregnant.

How to Use This Medicine:

Tablet

• Your doctor will tell you how much medicine to use. Do not use more than directed.
• Missed dose: This medicine needs to be given on a fixed schedule. If you miss a dose, call your doctor for instructions.
• Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

• Some medicines can affect how letrozole works. Tell your doctor if you are also using tamoxifen.

Warnings While Using This Medicine:

• It is not safe to take this medicine during pregnancy. It could harm an unborn baby. Tell your doctor right away if you become pregnant. Use an effective form of birth control during treatment with this medicine and for at least 3 weeks after the last dose.
• Do not breastfeed while you are taking this medicine and for at least 3 weeks after your last dose.
• Tell your doctor if you have liver disease (including cirrhosis), bone problems (including osteoporosis), or high cholesterol in the blood.
• This medicine may cause the following problems:
  • Low bone mineral density
  • High cholesterol or fat levels in the blood
  • Liver problems
• This medicine may make you dizzy, drowsy, or tired. Do not drive or do anything else that could be dangerous until you know how this medicine affects you.
• This medicine could cause infertility. Talk with your doctor before using this medicine if you plan to have children.
• Medicines used to treat cancer are very strong and can have many side effects. Before receiving this medicine, make sure you understand all the risks and benefits. It is important for you to work closely with your doctor during your treatment.
• Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.
• Keep all medicine out of the reach of children. Never share your medicine with anyone.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

• Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
• Bone pain
• Chest pain, trouble breathing, coughing up blood
• Dark urine, pale stools, nausea, vomiting, loss of appetite, stomach pain, yellow skin or eyes
• Numbness or weakness on one side of your body, sudden or severe headache, problems with vision, speech, or walking
• Pain in your lower leg (calf)
• Swelling in your ankles or feet
• Unusual bleeding or bruising
• Unusual tiredness or weakness

If you notice these less serious side effects, talk with your doctor:

• Breast pain
• Diarrhea, constipation, stomach pain
• Headache
• Increased sweating
• Mild joint, back, or muscle pain
• Trouble sleeping
• Vaginal bleeding
• Warmth or redness in your face, neck, arms, or upper chest
• Weight gain or loss

If you notice other side effects that you think are caused by this medicine, tell your doctor

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

Last Updated: 12/4/2023