Patient Education Quick Reference Guide Diablo Valley Oncology/Hematology Medical Group Phone Number: 925-677-5041

Uses For This Medication
  • Letrozole is used to treat breast cancer in postmenopausal women only.
  • This medication may also be given for other conditions as determined by your doctor.

How This Medication Works

Letrozole works by decreasing the amount of estrogen your body makes. Estrogen is a hormone that causes some breast cancer cells to grow. By decreasing the amount of estrogen in your body, the breast cancer cells which need estrogen to grow will not be able to grow.  

Benefits of This Medication

Letrozole is used to treat breast cancer several different ways. Letrozole can be used as additional treatment in postmenopausal women with breast cancer who have already received five years of treatment with tamoxifen. This is known as adjuvant therapy. It can also be beneficial in the treatment of breast cancer that has metastasized, or spread, to other parts of the body. Lastly, letrozole can be used in the treatment of advanced breast cancer in postmenopausal women who have not responded to other hormonal treatments such as tamoxifen (Nolvadex®).  

Who Should Not Take This Medication

You should not take this medication if you:
  • Are allergic to letrozole or any of its components

Precautions to be Aware of Before Taking This Medication

Activity related precautions

This medication may cause fatigue and dizziness. Use caution or avoid operating machinery, including driving a car, while taking this medication.

Organ related precautions

This medication is broken down by enzymes (chemicals) in the liver and cleared from the body. In patients with severe liver disease, letrozole may not break down normally which can lead to high levels of this medication in the body and a greater chance of side effects. If you have any liver problems before starting this medication, make sure that you tell your doctor or healthcare provider so that he or she can watch you carefully for possible problems or side effects.  

Patient specific precautions

  • It is not known if this medication is safe and effective in children.

Pregnancy and breastfeeding precautions

  • This medication may cause fetal harm. When taking this medication, you should use effective birth control to prevent pregnancy. You should not take hormonal birth control (pills, patches, rings, implants, injections) while on letrozole since this medication can stop hormonal birth control methods from working. Barrier type methods of birth control (condoms, diaphragms) should be used instead if needed. Tell your doctor or healthcare provider right away if you or your spouse/partner becomes pregnant.
  • It is not known whether this medication is found or excreted in breast milk. Since many medications are excreted in breast milk and because this medication can cause serious harmful reactions in infants, breastfeeding should be avoided.
  • Many anti-cancer therapies can cause sterility. Notify your doctor or healthcare provider if you want to have children in the future.

Medication and Food Interactions

Before using this medication, tell your doctor or healthcare provider of all prescription or over-the- counter products you are taking, including dietary supplements or vitamins, herbal medicines and homeopathic remedies. Do not start or stop any medication without your doctor or healthcare provider’s approval. Possible interactions can occur with letrozole and the following medications:
  • Tamoxifen (Nolvadex®)
  • Birth control pills or other estrogen containing medications
NOTE: This list may not include all medications that can have interactions with letrozole.

Side Effects

  • All medications can cause side effects. However, not all patients will experience these side effects. In addition, other side effects not listed can also occur in some patients. You should call your doctor or healthcare provider if you have any questions or concerns while you are on this medication.
  • You should contact your doctor or healthcare provider if you experience any side effect(s) which don’t go away, worsen, are serious in nature, or are worrisome to you.
  • Side effects can occur when letrozole is given alone or together with other chemotherapy medications. The side effects listed below are those reported in patients who were treated with letrozole alone.

More common side effects

  • Hot flushes
  • Fatigue (tiredness)
  • Nausea
  • Back pain, joint pain, bone pain
  • Shortness of breath, cough

Less common side effects

  • Constipation, diarrhea, vomiting, loss of appetite
  • Headache
  • Insomnia
  • Hypertension- high blood pressure

Rare side effects

This is not a complete list of the rare side effects reported with letrozole. For a complete list, please talk with your doctor or healthcare provider about reviewing a copy of the package insert.
  • Blood clots with redness or mild swelling of arms, legs and ankles, pain in leg calves, shortness of breath, difficulty breathing
  • Heart attack, angina (chest pain)
  • Stroke 
  • Osteoporosis, bone fractures 
  • Vaginal dryness, irritation

How To Take This Medication

  • This medication is taken by mouth (orally) with or without food. Take this medication exactly as directed by your doctor or healthcare provider. If you do not understand these instructions, ask your doctor or healthcare provider to explain them to you.
  • It is important that you only use this medication when it’s been prescribed for you. Sharing this medication with someone for whom it is not prescribed could cause harm.
  • If you miss a dose of letrozole, take it when you remember, then take the next dose as usual. If it is almost time for your next dose or you remember at your next dose, do not take extra tablets to make up the missed dose.
  • If you accidentally take too many pills or someone else accidentally takes your medication, contact your doctor, your local poison control center at 1-800-222-1222, or emergency services immediately.

Proper Storage

  • Store this medication at room temperature and keep in its original container.
  • Keep this medication out of the reach of children or pets.
  • Ask your doctor or healthcare provider how to dispose of any medication that you no longer use.