Letrozole (Oral)


Women who suffer from breast cancer during menopause have found effective relief with the use of the prescription drug called letrozole. This medication helps to halt the body's production of female hormones that contribute to the growth of many breast cancers. Letrozole is not typically used as the first treatment and follows the use of such anti-cancer drugs as tamoxifen.

This medication has been reported to cause a condition known as osteoporosis due to the tendency of letrozole to decrease the bone density of some patients. The likelihood of suffering from this condition increases the longer that letrozole is taken. Confer with your doctor on effective steps that you can take in order to forestall the development of this condition.

Letrozole should not be taken by women of childbearing age, and as it is typically used by women who are post-menopausal, this should not be of concern. Patients should be aware that the use of this medication can cause harm to a developing fetus, and if in the unlikely that a woman who is taking letrozole should become pregnant, they must notify their doctor right away.

Patients who are taking letrozole have been reported to develop elevated levels of cholesterol, a condition that can lead to further complications. Your doctor will likely monitor your health while taking letrozole and screen for such unwanted side effects like high cholesterol. This makes it important for patients to undergo all diagnostic testing, such as blood tests, as scheduled by their doctor.

Letrozole is not typically the first medication that the patient will receive in the treatment of their breast cancer. If you experience any difficulties or negative reactions while being treated with this medication, be sure to notify your doctor immediately. Likewise, if you do not feel that the drug is proving to be effective, or it is not working as expected, be sure to discuss these concerns with your doctor prior to making any changes to the way in which you take this medication.

Letrozole comes in this form of dosage delivery:

  • Tablet

Condition(s) Treated

  • Post-menopausal breast cancer

Type of Medicine

  • Female hormone retardant

Side Effects

Similar to many drugs, letrozole can cause some unwanted side effects in addition to its desired outcomes. Patients are advised to familiarize themselves with the types of symptoms that require further medical attention and be able to differentiate them from side effects that typically go away on their own without further medical attention. There are certain side effects and symptoms that will require further medical attention as they may be a sign of a more serious problem. Patients are encouraged to remain in close communication with their medical team while they are taking this medication.

If any of the following side effects occur it is important to notify your doctor as further medical attention may be warranted:

Less likely:

Rare likelihood:

  • Continuing or severe nervousness
  • Dizziness or lightheadedness
  • Slurred speech
  • Accelerated heartbeat
  • Severe and sudden, unexplained shortness of breath
  • An increase in sweating
  • Nausea
  • Pain in the chest
  • Groin pain
  • Leg pain
  • Vision changes
  • Severe, sudden headache
  • Heart attack
  • Any sudden and significant decrease in coordination ability
  • Fainting
  • Vaginal bleeding
  • Coughing
  • Changes in vision
  • Weakness or numbness in the extremities

An unknown incidence of occurrence:

  • Black, tarry stools
  • Irregular heartbeat
  • Weight gain
  • Blurred vision
  • Unusual bleeding or bruising
  • Chest discomfort
  • Decreased vision
  • Sores, ulcers, or white spots on the lips or in the mouth
  • Extreme fatigue
  • Passing urine more often
  • Irregular breathing
  • Painful or difficult urination
  • White or brownish vaginal discharge
  • Sore throats
  • Increased need to urinate
  • Swollen glands
  • Dilated neck veins
  • Unusual tiredness or weakness
  • Burning, crawling, itching, or numbness
  • Wheezing
  • Blindness

As your system adjusts to letrozole there will likely be some discomfort and symptoms may occur that will go away on their own. This group of symptoms will typically dissipate on their own after your system becomes used to the introduction of letrozole. Side effects that linger for more than a few days or become worse may require further medical care and your doctor should be notified in such instances:

More likely:

  • Joint pain
  • Back pain
  • Muscle pain
  • Hot flashes
  • Bone pain

Less likely:

  • Anxiety
  • Constipation
  • Spinning or whirling sensation causing loss of balance
  • Dry mouth
  • Skin rash or itching
  • Increased thirst
  • Weakness
  • Metallic taste
  • Loss of appetite or weight loss
  • Sleepiness
  • Headaches
  • Stomach pain or upset
  • Diarrhea
  • Vomiting
  • Confusion
  • Trouble sleeping

An unknown incidence of occurrence:

  • Bad, unusual, or unpleasant mouth taste
  • Red, sore eyes
  • Change in taste
  • Irritability
  • Hair loss
  • Hives or welts
  • Increased appetite
  • Swelling or inflammation of the mouth
  • Nervousness
  • Dryness of the skin
  • Redness of the skin
  • Being forgetful

While this list provides comprehensive information about the symptoms that can occur, you may experience symptoms that are not listed here. Patients are encouraged to discuss any concerns that they experience while taking letrozole with their doctor or pharmacist. If you feel that your symptoms are not getting better, or they are bothersome or cause you worry, contact the prescribing physician for further medical advice.


Depending on the preference and comfort of the patient, letrozole may be taken alone or with food.

The dosage guidelines that are outlined below represent the way in which letrozole is typically prescribed, although the instructions that you receive from your doctor may differ. Always follow the instructions that are provided with your prescription, and do not change the way that you take this medication without first consulting with your doctor.

Most patients who are taking letrozole as part of their course of treatment against breast cancer again will be prescribed:

  • 2.5 milligrams taken one time per day

Patients who miss a scheduled dosage should take their medication upon realizing that it has been skipped. However, in cases where it is near the time for the next scheduled dose, the missed pill should be skipped completely. Patients who are unsure of what to do in the event that they miss a scheduled dose should contact their pharmacist or physician for further instruction. Patients should not take a double dosage of letrozole under any circumstances.

Major Drug Interactions

Like many other prescription drugs, letrozole is contraindicated for use with other medications. It is important that your doctor is aware of all medicines that you are currently taking, including both prescription and non-prescription medications and any herbal remedies or vitamin and mineral supplements. If you are taking any of the drugs listed below your doctor may alter the way in which you take one or both of them in order to decrease the likelihood of experiencing any unwanted side effects.

Patients who are taking any of the medications that are listed below may have their prescription altered by their doctor in order to avoid any difficulties that can arise from taking them with letrozole, or they may alter the way in which you take one or both of the drugs:

  • Tegafur
  • Ceritinib
  • Idelalisib
  • Clarithromycin
  • Cilostazol

Patients who are also taking the cancer drug noted below may have their prescriptions altered in order to decrease the chance of unwanted side effects:

  • Tamoxifen

Notify your doctor of any allergies that you may have, including those to other medications, food, animals, cleaning products or other substances, as these may affect the way in which your body reacts to letrozole. Inform your doctor of any lifestyle habits that you may have, such as the use of tobacco products or alcohol, as these activities may affect the way that your body reacts to letrozole.

Patients that are also being treated for any of the following conditions may experience further complications when treated with letrozole. Your doctor should know of your comprehensive medical history, especially if you suffer from any of these ailments:

Letrozole should not be used by women who are pre-menopausal.


Women who are being treated with letrozole will likely require regular diagnostic testing in order to monitor the effectiveness of the medication and also to detect any unwanted side effects. It is important that patients who are taking letrozole keep all follow-up appointments and also undergo all diagnostic testing as ordered.

Due to the fact that letrozole is typically used in the treatment of postmenopausal women, the chance of pregnancy is not an issue. Patients are advised that the use of letrozole while pregnant can cause harm to the developing fetus, and women who become pregnant while taking letrozole should notify their doctor immediately.

While taking this medication, patients may experience a decrease in their bone mineral density, especially in cases where it is used over an extended period of time. This decrease can in certain situations lead to a condition known as osteoporosis. Patients will need to undergo regular screening for this condition and may be prescribed certain medications to minimize their chances of contracting it. Patients are encouraged to discuss this condition and the chances of developing it with their doctor prior to beginning their letrozole course of treatment.

Letrozole has been reported to increase the level of cholesterol or blood that is present in your bloodstream; should this occur your doctor may prescribe a medication to counterbalance this development, or they may advise certain changes to your diet.

Many patients have reported that their use of letrozole has caused them to become drowsy, feel dizzy and lightheaded, and generally experience a feeling of low alertness. Patients are advised to understand how letrozole affects them and to limit activities such as driving or operating heavy machinery if there is a chance that this medication causes them a reduced feeling of alertness.


Like all other medications, letrozole is best stored in its original packaging. Keep letrozole in a low-moisture environment; do not expose to direct light, or extreme heat or cold. Do not freeze letrozole.

Keep this and all medications out of the reach of small children and pets.

If at the completion of your course of treatment, you have unused, expired, or excess letrozole is disposed of safely. If you are unsure of the appropriate manner of disposal, confer with your pharmacist for further direction.


Women who suffer from breast cancer during menopause have found effective relief with the use of the prescription drug called letrozole. This medication helps to halt the body's production of female hormones that contribute to the growth of many breast cancers. Letrozole is not typically used as the first treatment and follows the use of such anti-cancer drugs as tamoxifen.

Patients who are being treated with letrozole for an extended period of time may be at a higher likelihood of developing osteoporosis or high cholesterol; two conditions that the prescribing doctor will typically screen for during the letrozole course of treatment. Patients are reminded to keep all follow-up appointments and undergo all diagnostic testing, such as blood tests, as scheduled.

Alert your doctor to any negative reactions that you may experience while taking letrozole as they can help to alleviate such circumstances.