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Letrozole (Generic Name)

UPMC Content 2

About This Drug

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

Possible Side Effects (More Common)

  • Nausea and throwing up (vomiting). These symptoms may happen within a few hours after your dose. Medicines are available to stop or lessen these side effects.
  • Hot flashes or night sweats
  • Joint or muscle pain or muscle weakness
  • Back pain or headache
  • Trouble catching your breath
  • Changes in how strong your bones are
  • High cholesterol levels

Possible Side Effects (Less Common)

  • Throwing up or loose bowel movements
  • High blood pressure
  • Trouble sleeping
  • Rash
  • Pain in the breast
  • Feeling dizzy
  • Swelling of ankles

Treating Side Effects

  • Ask your doctor or nurse about medicine that is available to help stop or lessen nausea and throwing up
  • If you get a rash, do not put anything it rash unless your doctor or nurse says you may. Keep the area around the rash clean and dry. Ask your doctor for medicine if your rash bothers you.
  • Let your doctor know if you have trouble sleeping.
  • Drink 6-8 cups of fluids each day unless your doctor has told you to limit your fluid intake due to some other health problem. A cup is 8 ounces of fluid. If you throw up or have loose bowel movements, you should drink more fluids so that you do not become dehydrated (lack water in the body from losing too much fluid).
  • Your doctor may order a bone density test to check how strong your bones are.
  • Your doctor will order blood work to check your cholesterol levels as needed.

Important Information

  • You may take this drug with or without food. If you have nausea, take it with food.
  • Swallow the pill whole.  Do not chew, break or crush it.
  • Do not let this drug get too cold or too hot.
  • Missed dose: If you miss a dose of this medicine, take it as soon as you remember. If it is close to the time of your next dose (within 2 to 3 hours), skip the dose you missed and take your next dose at your normal scheduled time. Do not take more than one dose at a time to make up for missed doses.

Food and Drug Interactions

This drug may interact with other medicines. Tell your doctor and pharmacist about all the medicines and dietary supplements (vitamins, minerals, herbs and others) that you are taking at this time. The safety and use of dietary supplements and alternative diets are often not known. Using these might affect your cancer or interfere with your treatment. Until more is known, you should not use dietary supplements or alternative diets without your cancer doctor's help.

When to Call the Doctor

Call your doctor or nurse right away if you have any of these symptoms:

  • Trouble breathing or feel short of breath
  • Nausea that stops you from eating or drinking
  • Throwing up more than three times in one day
  • Chest pain or you feel like your heart is beating too fast
  • Cramping or pain in your legs or swelling, redness or warmth of one leg 
  • Coughing up blood

Call your doctor or nurse as soon as possible if you have any of these symptoms:

  • Loose bowel movements (diarrhea) 5 or 6 times in one day or if you feel weak or lightheaded from having diarrhea
  • Nausea or loss of appetite that is not relieved with prescribed medicines  
  • Pain in your back, arms or headache that is not relieved with prescribed medicines
  • Loss or gain of more than 5 pounds in a week
  • Weakness or lack of strength that stops you from doing your normal activities
  • Stomach pain
  • Feeling tired all the time even if doing nothing
  • Rash that bothers you

Reproduction Concerns

  • Pregnancy warning: This drug may cause very harmful effects on an unborn child. Letrozole should never be used by women who are pregnant or who could become pregnant while taking the drug. Even 1 dose taken by a pregnant woman can cause these very harmful effects. Your healthcare team will talk to you and give you written information about this risk.
  • Breast feeding warning: It is not known if this drug passes into breast milk.  For this reason, women should talk to their doctor about the risks and benefits of breast feeding during treatment with this drug because this drug may enter the breast milk and badly harm a breast feeding baby.


Revised September 2014