Overview:

Letrozole is a widely employed medication that is primarily advised for treating breast cancer. The drug regulatory authority of the United States, the Food and Drug Administration (FDA), authorized the use of Letrozole in patients diagnosed with breast cancer. Letrozole attained FDA approval in the year 1998, and since then, it has been widely prescribed for those who are diagnosed with breast cancer in the advanced stage.

In 2004, the FDA also granted authorization for using Letrozole as an adjuvant therapy for early-stage breast cancer. However, its application is restricted to women who have attained menopause. It is now marketed and circulated under various brand names. It can be purchased from the pharmacies upon production of a doctor’s prescription.

Drug Group:

Letrozole is a nonsteroidal aromatase inhibitor. This drug class works by potentially reducing the level of the female hormone estrogen. The reduction in estrogen production happens through a series of steps. Once the estrogen level drops considerably, the breast cancer cells, which are largely dependent on this hormone, fail to thrive and advance.

Available Doses and Dosage Forms:

Letrozole is manufactured in a single dosage strength of 2.5 milligrams (mg). The medicine is intended for oral use and is available in tablet form. The FDA has approved no other drug form of Letrozole for treating breast cancer.

What Is Letrozole Used For?

Letrozole is an FDA-approved anticancer medicine typically used for hormone-positive breast cancer cases. However, it is not the preferred choice for all other types of breast cancer. Early-stage breast cancers that have hormone receptors are often considered for treatment with this particular drug. It is considered for those who no longer get their monthly menstruation; that is, they have attained the menopause stage.

It can sometimes be combined with other anticancer medicines as part of an integrative treatment approach. Even after breast cancer surgery, Letrozole might be given, at times, to deal with any leftover cancer cells from growing and spreading. Letrozole might also be advised as part of fertility treatments.

Despite its several critical therapeutic uses, one should also be vigilant about potential side effects. Letrozole side effects, like hot flashes, body pain, and heartburn, might also develop in between.

For Patients:

What Is Breast Cancer?

Breast cancer is a typical form of cancer where the breast cells show abnormal cell growth and multiplication. The person may notice a lump or thickening in their breast. Sometimes it also causes asymmetry or a change in their breast shape, and they may notice abnormal discharge, tenderness, and skin changes, especially in the nipple area.

Individuals over 50 years are more likely to develop it. However, that doesn’t mean it will never develop at younger ages; it does. Breast cancer development is influenced by specific gene mutations. Along with genetic changes, hormonal and lifestyle factors also influence development.

If you have a family history of breast cancer, then it’s best to get it screened. Periodic screening will definitely help detect the condition in its early stages.

What Is Letrozole?

Letrozole is a potent anticancer medicine used in tablet form. It is typically used for treating certain breast cancer subtypes that are mostly in their initial or early stage. It can significantly reduce the production of the hormone estrogen. Letrozole uses this property to fight against certain breast cancers that are dependent on estrogen.

This medicine is available in tablet form, making it easy for the patient to take it on their own. Its uses are not just limited to breast cancer; certain other conditions, like female infertility treatment, also use Letrozole; however, it is an off-label use as it's not actually approved by the FDA for those conditions.

How Does Letrozole Work?

Being a nonsteroidal aromatase inhibitor, Letrozole mitigates the bodily estrogen level. Letrozole is found to be effective for those breast cancers that are responsive to estrogen. The drug molecule interacts with an enzyme involved in estrogen synthesis. The interaction blocks the enzyme activity, thereby checking estrogen production. In this way, Letrozole makes the cancer cells starve for estrogen and checks further proliferation.

Letrozole can also work as an ovulation inducer by lowering the estrogen level. Once estrogen levels drop, the ovarian environment becomes favorable for ovulation, thereby promoting it. Letrozole fertility treatments use this property, and that is why doctors sometimes advise it to deal with female infertility, though off-label.

What Is the Dosage of Letrozole?

The generally prescribed daily dosage of Letrozole is 2.5 mg. It is often advised to be taken as a single dose. However, the dosage may need to be adjusted in the presence of other underlying health conditions. The patients are strictly instructed to adhere to the dosage regimen prescribed by their respective doctors. Altering the dosage without medical consultation can make the drug ineffective or can bring in adverse complications.

How Effective Is Letrozole?

Letrozole is proven to be efficacious against estrogen-responsive breast cancer. In fact, it considerably reduces the rate at which breast cancer is spreading in the body. Not only that, but it also minimizes the breast cancer recurrence possibilities. Its ability to limit recurrence is far greater than that of standard therapies like Tamoxifen. If you are confused about the suitability of Letrozole for your breast cancer treatment, consult an oncologist at iCliniq.

How Should I Use Letrozole?

Letrozole must be used according to the guidelines and recommendations of the concerned medical personnel. Take only the precise dose prescribed by the doctor, and never try to alter it. Stick to the prescribed Letrozole dosage and dosing frequency. Take Letrozole orally as it is in tablet form; there is no other formulation in which it has been used therapeutically.

What Are the Things to Inform the Doctor Before Taking Letrozole?

Before initiating any treatment, it is necessary to have a proper discussion with your doctor. It enables the doctor to establish rapport with patients and facilitates treatment.

Previous hypersensitivity reactions to Letrozole or any of the components listed in the Letrozole pill ingredients need to be reported before initiation of Letrozole therapy. Subsequent exposure to the allergen can trigger severe adverse reactions.
It is very important to provide a comprehensive medical history of the patient. Understanding the patient's health status helps the concerned doctors choose the right medicine for the person’s condition. The medical history should highlight the person’s underlying health conditions, their past surgeries, and all other health-related events. Liver diseases, osteoporosis (impaired bone density), and elevated cholesterol levels must be brought to the doctor’s attention before getting into the therapy using Letrozole.
A detailed drug history encompassing all medications, which could be herbal, non-prescription, hormonal, or dietary supplements, needs to be provided so that unpleasant drug-to-drug associations can be avoided. Hormonal contraceptives and other hormonal therapies require special emphasis, and the doctor should be informed about them.
Letrozole is indicated for reproductively inactive women who have attained menopause and not for reproductively active females. Letrozole is not safe during pregnancy, and if the patient is still capable of conception, the doctor should be made aware of it.

How Is Letrozole Administered?

Letrozole should be taken orally, preferably with water. The pill should always be intact and not chewed; it should be consumed whole. It is better to stick to a specific time for the pill administration, as it aids in keeping the drug concentration consistent throughout the treatment regimen.

What Are the Side Effects of Letrozole?

Letrozole can bring in so many adverse effects. Some effects are minor, while some are alarming and necessitate medical attention.

Some of the frequently encountered Letrozole side effects include the following:

Digestive issues like constipation, diarrhea, loss of appetite, vomiting, and acid reflux (heartburn).
Hormonal issues like hair loss, night sweats, hot flashes (experiences sudden intense heat), and altered body weight.
Other side effects include body pain, stomach pain, headache, impaired vision, breast pain, tiredness, puffy arms and legs, tiredness, troubled sleeping, and vaginal bleeding.

In addition, Letrozole may also bring about certain alarming adverse reactions in the form of extensive skin rashes, troubled breathing, abnormal skin bruising, yellowish skin, slurred speech, severe tiredness, and collapse. In such reactions, immediate medical care is required. Letrozole can cause high blood sugar levels. This increases the person’s risk of getting diabetes. Letrozole’s interactions with other medicines can also cause certain adverse reactions; therefore, before combining any medicine, contact your doctor to ensure it is safe.

What Letrozole Precautions Should I Follow?

While on Letrozole therapy, taking certain precautionary measures is critical and helps keep complications at bay.

When targeting breast cancer treatment, Letrozole is for post-menopausal women and is not meant for those with reproductive potential.
Letrozole tends to reduce bone strength. Periodic bone density assessment can be done as a precautionary measure to monitor how Letrozole affects bone density.
Similarly, Letrozole can impair one's consciousness and cause dizziness; therefore, refrain from activities where dizziness could be detrimental.
It can also elevate the cholesterol level, so that must be kept in mind. Periodically check if it's within the healthy limit. If not, get medicine for elevated cholesterol.

Dietary Considerations:

There are no specific dietary instructions to follow. The presence of food does not appear to significantly alter the mechanism of action of Letrozole. However, given underlying medical conditions, doctors may advise dietary restrictions for some patients, which should be followed without fail.

Missed Dose:

Proper adherence to the treatment regimen is essential to ensure the effectiveness of Letrozole. However, the patient may sometimes need to remember to administer the dose. If a dose is missed, it can be taken once the patient becomes aware of the missed pill. However, if the patient recalls the missed dose at the time of the next dose, it is advised to forgo it. No attempt should be made to alter the drug dosage to cover up for the dose that was missed in between.

Overdose:

Consuming more than the safe dosage of Letrozole can bring in potential overdose issues. There is not much information available concerning its overdose effects. Emesis (induced vomiting) helps in throwing up the gut content, which helps during an overdose. Following this, the patient should be monitored to assess vital parameters and ensure normal organ function.

Storage:

Letrozole is available in both blister packaging and medicine bottles. You can keep the medicine in the same packaging until it's time to have it. 25 degrees Celsius (77 degrees Fahrenheit) is the ideal temperature recommended for Letrozole storage. However, storage at 15 to 30 degrees Celsius (59 to 86 degrees Fahrenheit) is also reported to be safe. Always ensure the medicine is within its expiry date. Medicines that are out of date can be disposed of through drug take-back programs.

For Doctors:

Indications:

Early Breast Cancer: Letrozole is employed as adjuvant therapy for dealing with early-stage breast cancers that test positive for hormone receptors. It is also indicated for extended adjuvant therapy, following adjuvant therapy using Tamoxifen for a period of five years.
Advanced Breast Cancer: Metastatic breast cancers and locally advanced breast cancers, which are hormonally responsive, are indicated with Letrozole therapy as both the first and second line of therapy.

Dose:

A daily dose of 2.5 milligrams of Letrozole is the preferred dosage schedule for breast cancer patients. The dosage remains the same for all patients. However, the duration of the therapy is determined by taking into consideration the stage of the breast cancer.

Dosing Considerations:

The dosing frequency is adjusted based on the functional status of other vital organs, such as the kidneys and liver. Patients with moderately compromised liver function will tolerate a daily dose of 2.5 milligrams of Letrozole. However, the presence of severe liver dysfunction and liver cirrhosis mandates dose reduction, and hence, the frequency of intake is extended to alternate days instead of daily. Similarly, dosage depreciation is advised for kidney patients with creatinine clearance rates below 10 milliliters per minute.

Why Is Letrozole Prescribed?

Letrozole is prescribed primarily because of its ability to reduce the estrogen level by bringing down its production. When the cancer growth is dependent on estrogen, using Letrozole can deprive the cancer cells of estrogen. Thus, using Letrozole can effectively reduce or even stop cancer cell growth. It works well even as adjuvant therapy, and for breast cancers that have grown into other organs and areas, like metastatic ones, Letrozole can be prescribed as the first line of treatment choice. Aromatase inhibition is the mechanism of action of Letrozole, which makes Letrozole versatile and a potent drug choice for postmenopausal breast cancer cases.

What Are the Pharmacological Aspects of Letrozole?

Mechanism of Action: A specific category of breast cancers is hormonally responsive. In hormonally responsive breast cancers, the cancer cells are fed by hormones like estrogen and progesterone. Therefore, by checking the hormonal availability, the cancer growth and progression can be hampered and impeded significantly. This principle is being employed by using Letrozole for breast cancer. Adrenal androgens are the primary source of estrogen in women who have attained menopause. Adrenal androgens are acted upon by the aromatase enzyme, which facilitates estrogen synthesis. Letrozole works by inhibiting the aromatase enzyme, thereby reducing estrogen production. Structurally and functionally modified aromatase enzymes fail to metabolize adrenal androgens, thereby curtailing estrogen production. Once estrogen levels are depleted, cancer cell growth will be directly inhibited. Thus, Letrozole effectively halts progression.
Pharmacodynamics: Aromatase inhibition elicited by Letrozole is highly precise, so the adrenal steroidogenesis process is left unhindered. Other bodily hormones, such as thyroid hormone, luteinizing hormone, aldosterone, and follicle-stimulating hormone, remain unchanged. The decline in estrogen levels is directly influenced by the dosage of Letrozole administered.
Pharmacokinetics: Following oral intake, Letrozole reaches the intestine, where it is rapidly absorbed into the bloodstream. 1.9 liters (64.24 ounces) per kilogram (2.20 pounds) is reported to be the Letrozole’s mean volume of distribution. Liver microsomal enzymes, particularly CYP3A4 (cytochrome P3A4) and CYP2A6, are involved in the breakdown of Letrozole drug molecules. A major proportion of the breakdown product is the carbinol metabolite, while ketone analogs and other metabolic products are also identified in smaller proportions. Urine is the primary route of elimination for Letrozole.

Toxicity:

There are fewer instances of clinical toxicity, and no grave toxicity issues have been reported to date. Limited information is available concerning the mutagenic and carcinogenic properties of Letrozole. However, nonclinical study reports revealed Letrozole’s potential for inducing hepatocellular and ovarian cancers when tested at a higher dosage level.

Clinical Studies:

Various clinical studies and trials have been conducted to evaluate the efficacy of Letrozole in dealing with hormone-sensitive breast cancers. Randomized comparative clinical trials of Tamoxifen and Letrozole showed that the therapeutic benefits of Letrozole were on par with those of Tamoxifen. Certain studies demonstrated Letrozole’s upper hand in checking and delaying the recurrence of breast cancer lesions following long-term therapy. The studies conducted on advanced breast cancer patients diagnosed with either metastatic breast cancer or locally advanced cancer flagged an appreciable rise in the survival rate when compared with subjects who were trialed with Tamoxifen therapy for the same duration. Numerous clinical studies have unequivocally proved the safety and effectiveness of Letrozole.

What Are the Contraindications of Letrozole?

Letrozole possesses certain potential contraindications and is not advised for all categories of breast cancer patients.

Some of the contraindications for Letrozole include the following:

Letrozole Allergy: Patients with prior allergic reactions to Letrozole are not eligible for Letrozole therapy. Previous hyperreactivity to any of the components of the Letrozole pill is also a potential threat to allergic response upon Letrozole therapy initiation.
Pregnancy: Letrozole is designed and advised for post-menopausal women and not for premenopausal women, who are particularly in the reproductive age group. Letrozole can bring deleterious effects on the baby in the womb when taken during pregnancy. Therefore, expectant women are not supposed to undergo Letrozole therapy. In addition, if the patient is planning for conception in the near future, they are also contraindicated for Letrozole therapy.

Warnings and Precautions:

Compromised Liver Functions: Impaired liver function can increase exposure to Letrozole. So in such cases, appropriate dose adjustments must be made.
Disparities in Blood Profile: Letrozole can also alter blood cell counts in some patients. In most cases, the count goes down, especially the lymphocyte count. Once medication is stopped, the count often returns to its normal level.
Dizziness: Letrozole can cause sleepiness, compromising the patient’s ability to perform activities that require fine motor skills and concentration. The patient should be warned, as it may lead to unexpected consequences.
Hyperlipidemia: In certain studies, it was found that Letrozole can increase the risk for hyperlipidemia. It is better advised to monitor the patient's lipid profile while on treatment with it.
Reduction in Bone Density: Long-term use of Letrozole can negatively affect bone density. Its impact is greater if the patient is already having reduced bone density. So periodic bone density monitoring is very important.

What Are the Drug Interactions of Letrozole?

When administered simultaneously with other medicines, Letrozole can precipitate unwanted effects and may alter the efficacy of either medicine. When administered concurrently, Letrozole and Tamoxifen result in a collapsed Letrozole concentration, impairing Letrozole’s efficacy and preventing the desired results from being attained. No reliable sources of information on the interaction between Letrozole and other anticancer medicines are available, and this needs to be further explored.

Use in Specific Population:

Letrozole During Pregnancy: Letrozole should not be taken during pregnancy. It can cause fetal harm and is, hence, strictly contraindicated. In case it is advised for someone who hasn't attained menopause, adequate contraceptive measures should be in place.
Letrozole During Lactation: Lactating women are generally not given Letrozole, as there is no clear information on its excretion into breast milk.
Letrozole in Geriatric Patients: There aren't many differences in efficacy observed with Letrozole in geriatric patients. However, older individuals often have other concurrent illnesses, which may require dose adjustments.

Letrozole Tablet - Indications, Pharmacology, and Warnings