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Letrozole (Femara®)

OncoLink Team
Last Modified: January 6, 2016

Pronounced: LET-roe-zole
Classification: Aromatase Inhibitor

About Letrozole

Letrozole is an aromatase inhibitor, which works to decrease the overall levels of estrogen in a woman's body. In women who have gone through menopause, estrogen is mainly produced by converting androgens (sex hormones produced by the adrenal glands) into estrogens. An enzyme called aromatase is responsible for this conversion. Aromatase inhibitors block this conversion, leading to less estrogen in the body. While estrogen may not actually cause breast cancer, it is a necessary hormone for the cancer cells to grow in estrogen receptor-positive breast cancers. With estrogen blocked, the cancer cells that feed off estrogen may not be able to survive.

How to Take Letrozole

Letrozole comes in tablet form and is taken by mouth once daily. Letrozole can be taken with or without food. If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose. Do not take two dosses at the same time.  Do not stop taking anastrozole without talking to your healthcare team.

Storage and Handling

Store this medication at room temperature in the original container. If you prefer to use a pillbox, discuss this with your oncology pharmacist. Ask your oncology team where to return any unused medication for disposal. Do not flush down the toilet or throw in the trash.

Where do I get this medication?

Depending on your prescription medication coverage, you may be able to receive this medication at a retail or mail order pharmacy or through a specialty pharmacy. Your oncology team will work with your prescription drug plan to identify an in-network specialty/retail/mail order pharmacy for medication distribution. 

Insurance Information

This medication may be covered under your prescription drug plan. Patient assistance may be available to qualifying individuals without prescription drug coverage. Co-pay cards, which reduce the patient’s co-pay responsibility for eligible commercially (non-government sponsored) insured patients, may also be offered by the manufacturer. Co-pay assistance from private third party foundations may be available. Your care team can help you access these resources, if they are available.

Possible Side Effects of Letrozole

There are a number of things you can do to manage the side effects of letrozole. Talk to your doctor or nurse about these recommendations. They can help you decide what will work best for you. These are some of the most common side effects:

Hot Flashes

There are a few things you can do to help with hot flashes. Several medications have been shown to help with symptoms, including clonidine (a blood pressure medication), low doses of certain antidepressants (such as venlafaxine and Prozac), and gabapentin. Non-medical recommendations include:

  • Keep well-hydrated with eight glasses of water daily.
  • Drink ice water or apply an ice pack at the onset of a hot flash.
  • Wear cotton or lightweight, breathable fabrics and dress in layers so you can adjust as needed.
  • Exercise on a regular basis.
  • Try practicing meditation or relaxation exercises to manage stress, which can be a trigger.
  • Avoid triggers such as warm rooms, spicy foods, caffeinated beverages, and alcohol.

Weakening of the Bones (Osteoporosis)

Your doctor will check your bone health before starting therapy. This is done with a bone density scan (dexa scan). Women with no weakening of bones prior to aromatase inhibitor therapy will have a follow-up scan around one year after starting therapy, and then every one to two years.

If the scan shows that you already have some bone weakening, your doctor may order a type of medication called a bisphosphonate or calcium and vitamin D supplements to help strengthen the bones. These therapies have been shown to protect the bones from bone loss in women taking aromatase inhibitors. If the bone density remains stable, scans can then be done every two years. In addition, weight bearing exercise and a healthy diet rich in calcium and vitamin D can help protect bone health.

Muscle or Joint Pain/Aches

Aromatase inhibitor medications can cause joint or muscle aches and pains, which can interfere with quality of life. Be sure to talk to your oncology team if you develop this side effect. This pain is caused mainly by swelling in the joints, which is best treated by a non-steroidal anti-inflammatory (NSAID), such as ibuprofen, naprosen and celecoxib. Be sure to discuss which pain relievers you can safely take with your oncology team, as these are not without their own side effects. Studies have shown that acupuncture and gentle stretching and exercise may also help reduce this pain.

Increased Blood Cholesterol

Letrozole can cause an increase in your cholesterol levels. Your healthcare team will monitor your cholesterol levels throughout you treatment.   

Liver Toxicity

This medication can cause liver toxicity, which your doctor may monitor for using blood tests called liver function tests. If you develop elevations in your liver function tests, your healthcare provider may need to lower your dose or stop the medication. Notify your healthcare provider if you notice yellowing of the skin or eyes, your urine appears dark or brown or pain in your abdomen, as these can be signs of liver toxicity.

Nausea and/or Vomiting

Talk to your doctor or nurse so they can prescribe medications to help you manage nausea and vomiting. In addition, dietary changes may help. Avoid things that may worsen the symptoms, such as heavy or greasy/fatty, spicy or acidic foods (lemons, tomatoes, oranges). Try antacids, (e.g. milk of magnesia, calcium tablets such as Tums), saltines, or ginger ale to lessen symptoms.

Call your doctor or nurse if you are unable to keep fluids down for more than 12 hours or if you feel lightheaded or dizzy at any time.

Vaginal Dryness

Vaginal dryness and related painful intercourse is one of the more common side effects of cancer therapy in women. Vaginal lubricants and moisturizers (longer lasting form of moisturizers) can help with these concerns. Talk to your healthcare team for more suggestions in managing this side effect.

Other Side Effects

Some patients report fatigue, dizziness and drowsiness when taking this medication. Use caution driving or operating machinery until you know how the medication affects you.

In rare cases, patients developed blood clotting issues, including blood clots (in the legs and lungs), stroke and heart attack. If you develop any swelling or pain in one leg or calf, shortness of breath, racing heart or chest pain, you should be evaluated by a healthcare professional right away.

Reproductive Concerns

Exposure of an unborn child to this medication could cause birth defects, so you should not become pregnant or father a child while on this medication. Effective birth control is necessary during treatment. Even if your menstrual cycle stops or you believe you are not producing sperm, you could still be fertile and conceive. You should consult with your healthcare team before breastfeeding while receiving this medication.