Letrozole (Femara®)

About This Drug

Letrozole is used to treat cancer. It is given orally (by mouth).

Possible Side Effects

  • Hot flashes or sudden skin flushing may happen. You may also feel warm or red.
  • Joint, muscle and bone pain
  • Headache
  • Weakness
  • Swelling of your legs, ankles and/or feet
  • Feeling dizzy
  • Increase in your cholesterol level.
  • Increased sweating

Note: Each of the side effects above was reported in 20% or greater of patients treated with letrozole. Not all possible side effects are included above.

Warnings and Precautions

  • Decrease in your bone mass, which may put you at risk of bone fractures
  • Increase in your cholesterol level

Important Information

  • This drug may impair your ability to drive or use machinery. Use caution and tell your nurse or doctor if you feel dizzy or very sleepy.

How to Take Your Medication

  • Swallow the medicine whole with or without food.
  • Missed doses: If you vomit or miss a dose, contact your doctor for further instructions. Do not take 2 doses at the same time or extra doses.
  • Handling: Wash your hands after handling your medicine, your caretakers should not handle your medicine with bare hands and should wear latex gloves.
  • This drug may be present in the saliva, tears, sweat, urine, stool, vomit, semen, and vaginal secretions. Talk to your doctor and/or your nurse about the necessary precautions to take during this time. 
  • Storage: Store this medicine in the original container at room temperature.
  • Disposal of unused medicine: Do not flush any expired and/or unused medicine down the toilet or drain unless you are specifically instructed to do so on the medication label. Some facilities have take-back programs and/or other options. If you do not have a take-back program in your area, then please discuss with your nurse or your doctor how to dispose of unused medicine.

Treating Side Effects

  • Keeping your pain under control is important to your well-being. Please tell your doctor or nurse if you are experiencing pain.
  • Get regular exercise. If you feel too tired to exercise vigorously, try taking a short walk.
  • If you are dizzy, get up slowly after sitting or lying.

Food and Drug Interactions

  • There are no known interactions of letrozole with food.
  • This drug may interact with other medicines. Tell your doctor and pharmacist about all the prescription and over-the-counter medicines and dietary supplements (vitamins, minerals, herbs and others) that you are taking at this time. Also, check with your doctor or pharmacist before starting any new prescription or over-the-counter medicines, or dietary supplements to make sure that there are no interactions.

When to Call the Doctor

Call your doctor or nurse if you have any of these symptoms and/or any new or unusual symptoms:

  • Headache that does not go away
  • Feeling dizzy or lightheaded
  • Pain that does not go away, or is not relieved by prescribed medicines
  • Weight gain of 5 pounds in one week (fluid retention)
  • Extreme weakness that interferes with normal activities
  • Swelling of your legs, ankles and/or feet
  • If you think you may be pregnant

Reproduction Warnings

  • Pregnancy warning: This drug may have harmful effects on the unborn baby. Women of childbearing potential should use effective methods of birth control during your cancer treatment and for at least 3 weeks after treatment. Let your doctor know right away if you think you may be pregnant.
  • Breastfeeding warning: Women should not breastfeed during treatment and for 3 weeks after treatment because this drug could enter the breast milk and cause harm to a breastfeeding baby. 
  • Fertility warning: In men and women both, this drug may affect your ability to have children in the future. Talk with your doctor or nurse if you plan to have children. Ask for information on sperm or egg banking. 

Revised July 2019

This patient information was developed by Via Oncology, LLC © 2019. This information is not intended to be used as a substitute for professional medical advice, diagnosis, or treatment. You should not rely entirely on this information for your health care needs. Ask your own doctor or health care provider any specific medical questions that you have.

CLIENT acknowledges that the Via Pathways and Via Portal are information management tools only, and that Via Oncology, LLC has not represented the Via Pathways or Via Portal as having the ability to diagnose disease, prescribe treatment, or perform any other tasks that constitute the practice of medicine. The clinical information contained in the Via Pathways and Via Portal are intended as a supplement to, and not a substitute for, the knowledge, expertise, skill, and judgment of physicians, pharmacists and other healthcare professionals involved with patient care at CLIENT facilities.