Letrozole: Uses Applications and Side Effects

What is a Letrozole?

Letrozole is a medication used to treat breast cancer in postmenopausal women. It is also used to prevent the cancer from returning. The brand name for letrozole is Femara.

Letrozole is a type of hormone therapy drug which works by lowering the levels of the hormone oestrogen in the body. This slows or stops the growth of breast cancer cells which need oestrogen to spread.

How Does Letrozole Work?

Letrozole is a versatile medication that works in different ways depending on the condition it’s treating. Here’s a breakdown of its mechanisms:

For Breast Cancer in Postmenopausal Women:

Letrozole is taken orally and acts as an aromatase inhibitor. Aromatase is an enzyme in the body responsible for producing estrogen. By blocking this enzyme, Letrozole significantly reduces estrogen levels. This is crucial because some breast cancers rely on estrogen to grow and spread. With lower estrogen levels, the growth of these cancer cells slows down or even stops.

For Fertility Issues:

In women struggling to conceive due to ovulation problems, Letrozole can be a helpful tool. It works by influencing hormone levels in a way that stimulates the ovaries. This can lead to the development and release of multiple eggs during ovulation, increasing the chances of natural conception.

How to Use Letrozole Tablet?


Letrozole comes in tablet form and is typically taken by mouth once a day. The good news is you can take it with or without food, whichever works best for you. The usual dose is 2.5mg.

Here’s a breakdown depending on why you’re taking Letrozole:

  • Fertility: If you’re using Letrozole to help with ovulation, it’s recommended to take the tablets for five days in a row. Ideally, this would be on days 3, 4, 5, 6, and 7 of your menstrual cycle. However, some doctors might suggest days 5, 6, 7, 8, and 9 instead. To increase your chances of conception, it’s recommended to have sex one to three days before you ovulate.
  • Breast Cancer: For postmenopausal women with breast cancer, the dose is also 2.5mg daily. You’ll continue taking it until your doctor determines otherwise.

What are the Side Effects of Letrozole?

Letrozole’s side effects include:

  • Hot flushes
  • Sweating
  • Nausea
  • Muscle, joint or bone pain
  • Sleep disturbances
  • Low mood or depression
  • Vaginal bleeding or dryness
  • Fatigue or tiredness
  • Hair loss
  • Dizziness
  • Increased cholesterol levels
  • Headaches
  • Constipation
  • Diarrhoea
  • Allergic reactions
  • Difficulty breathing
  • Blood clots
  • Stroke
  • Heart problems
  • Osteoporosis

Some side effects are more serious, so if you experience any of the following, you should call a doctor immediately:

  • Difficulty breathing, unusual bleeding or bruising
  • Pain in the upper right part of the stomach
  • Yellowing of the skin or eyes
  • Swelling, warmth or redness in a leg or arm
  • Sudden speech problems, or sudden weakness or numbness in any part of your body
  • Very sudden chest pain
  • Rashes
  • Hives
  • Fast or troubled breathing

    What are the Warning and Precautions of the Letrozole?

Here are some important precautions and warnings to be aware of before taking letrozole:

Letrozole is not suitable for anyone who is pregnant, or who may become pregnant. It can cause harm to the unborn child. A negative pregnancy test must be required before starting treatment.

Do not breastfeed while taking this medication, as it may harm the infant.

Letrozole may reduce fertility, so speak to your doctor if you plan to get pregnant.

Avoid taking estrogen containing medications, such as hormone replacement therapy or birth control pills, while taking letrozole.

Tell your doctor if you have any of the following: osteoporosis, high cholesterol, liver disease, or kidney problems.

Letrozole may cause dizziness or tiredness, so do not drive or operate machinery until you know how it affects you.

Contact your doctor immediately if you experience any of the following side effects: allergic reactions, difficulty breathing, unusual bleeding or bruising, chest or jaw pain, blurred vision, sudden weakness or numbness.

How Does Letrozole Interact with Other Medicines?


Letrozole can interact with certain medications, so it’s vital to talk to your doctor about everything you’re taking, including prescriptions, over-the-counter meds, and herbal supplements. Here’s what you need to know:

Medications to Avoid:

  • Menopause Treatments: Letrozole won’t work as well if you take medications for menopause symptoms, such as hormone replacement therapy (HRT) or estrogens like ethinyl estradiol and conjugated estrogens.
  • Other Medications: There are also some specific medications that may not mix well with Letrozole. Examples include anti-seizure medications (like aripiprazole and pimozide), certain heart medications (like dofetilide), and some pain medications (like hydrocodone or methadone).

Herbal Remedies:

It’s also best to avoid herbal remedies or supplements for menopause while taking Letrozole, as they might interfere with how it works.

Discrepancies in Information:

There can be some confusion online about Letrozole interactions. Some sources may say there are no major interactions, while others list medications to use with caution.

Here is a List of Complete Medication Interaction with Letrozole

Here’s what we recommend:

  • Always disclose all your medications and supplements to your doctor, including even common ones like Vitamin C or Aspirin.
  • They can review your specific situation and medications to determine if there are any potential interactions and advise you accordingly.

Some Medications Mentioned Online:

Here are some medications that have been mentioned online regarding interactions with Letrozole. It’s important to note that this is not a complete list, and your doctor will be able to provide specific advice on your situation.

  • Tibolone
  • Anastrozole
  • Tamoxifen
  • Duloxetine
  • Lexapro (escitalopram)
  • Lipitor (atorvastatin)
  • Nexium (esomeprazole)
  • Synthroid (levothyroxine)
  • Zofran (ondansetron)

What Happens if I Miss a Dose of Letrozole?

If you forget to take a dose of letrozole, most sources recommend taking it as soon as you remember, as long as it’s within 12 hours of the missed dose. If more than 12 hours have passed, it’s best to skip the missed dose and stick to your usual dosing time. Do not take a double dose to make up for a missed dose.

What Happens if I Overdose on Letrozole?

According to sources, the consequences of a letrozole overdose are unclear. It’s recommended that you seek immediate medical attention or call the local Poison Control Centre if you think you have overdosed on letrozole. Symptoms of overdose may include those associated with the common side effects, listed above, but there is little information on what to expect in such a scenario.

In cases of overdose, emesis could be induced if the patient is alert, and supportive care and frequent monitoring of vital signs would be appropriate.

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