What is Letrozole?

Letrozole is an oral nonsteroidal aromatase inhibitor primarily used in the management of hormone receptor‑positive breast cancer in postmenopausal women. It works by inhibiting the aromatase enzyme responsible for converting androgens into estrogens, thereby significantly reducing estrogen levels that drive the growth of certain breast cancers.

Reference: U.S. FDA Femara Prescribing Information; PubMed (Lønning & Eikesdal, 2011)

What are the other popular and common names for Letrozole?

Letrozole is most commonly marketed under the brand name Femara®. It is widely recognized in clinical practice and literature by both its generic name (letrozole) and its brand name, Femara.

Reference: MedlinePlus; U.S. FDA

What is the drug classification of Letrozole?

Letrozole is classified as an aromatase inhibitor. It belongs to the group of nonsteroidal aromatase inhibitors used in oncology for the treatment of estrogen‑dependent breast cancers.

Reference: World Health Organization (WHO) Oncology Guidelines; U.S. FDA

What is the mode of action of Letrozole?

Letrozole functions by competitively inhibiting the aromatase enzyme. This inhibition prevents the conversion of androgens (androstenedione and testosterone) into estrogen, leading to lower circulating estrogen levels. The reduced estrogen concentration limits the growth stimulus for estrogen‑dependent tumors.

Reference: PubMed (Lønning & Eikesdal, 2011); U.S. FDA

What are the primary uses of Letrozole?

Letrozole is primarily used for:

• Advanced or Metastatic Breast Cancer: Treating hormone receptor‑positive breast cancer in postmenopausal women who have progressed on or are intolerant to other therapies.
• Adjuvant Therapy: Reducing the risk of recurrence in early-stage hormone receptor‑positive breast cancer following surgery.
• Off‑Label Uses: It is sometimes used off‑label for ovulation induction in women with polycystic ovary syndrome (PCOS) under strict medical supervision.

Reference: U.S. FDA; National Comprehensive Cancer Network (NCCN) Guidelines; WHO

What is the recommended dosage and administration for Letrozole?

• Dosage for Breast Cancer: The typical dosage is 2.5 mg once daily, taken orally.
• Administration:
  • Letrozole can be taken with or without food.
  • It should be taken at the same time each day to maintain steady drug levels.
• Dosage for Ovulation Induction (Off‑Label): The dosing regimen may differ and should be determined by a specialist.

Reference: U.S. FDA Femara Prescribing Information; ClinicalTrials.gov

What prescribing information is important for Letrozole?

• Indications:
  • Letrozole is indicated for the treatment of hormone receptor‑positive advanced breast cancer and as adjuvant therapy in early breast cancer in postmenopausal women.
• Contraindications:
  • It is contraindicated in premenopausal women and during pregnancy due to its teratogenic potential.
• Monitoring:
  • Regular monitoring of liver function, lipid profiles, and bone mineral density (in long‑term therapy) is recommended.
• Special Considerations:
  • Patients should undergo hormonal receptor testing to confirm estrogen dependence before initiation.

Reference: U.S. FDA Femara Prescribing Information; NCCN Guidelines; WHO

What safety information, side effects, warnings, and cautions are associated with Letrozole?

• Common Side Effects:
  • Hot flashes, joint pain, fatigue, and nausea.
  • Increased cholesterol levels and risk of osteoporosis with long‑term use.
• Serious Side Effects:
  • Osteoporosis and bone fractures, especially in long‑term treatment.
  • Hepatotoxicity, although rare, can occur; liver function tests should be monitored.
• Warnings & Cautions:
  • Bone Health: Long‑term use may lead to decreased bone mineral density. Supplemental calcium and vitamin D may be advised.
  • Cardiovascular Risk: Monitor lipid levels as treatment may lead to hypercholesterolemia.
  • Pregnancy: Letrozole is contraindicated in pregnancy and lactation due to teratogenic effects.
• Additional Cautions:
  • Avoid use in patients with a history of liver disease unless benefits outweigh risks.

Reference: U.S. FDA; PubMed (Lønning & Eikesdal, 2011); NCCN Guidelines

What drug interactions should be considered with Letrozole?

• CYP450 Interactions:
  • Letrozole is metabolized by the liver, primarily via CYP3A4. Strong inhibitors (e.g., ketoconazole) or inducers (e.g., rifampin) of CYP3A4 may affect its plasma levels.
• Other Hormonal Agents:
  • Concomitant use with other hormone therapies should be carefully monitored to avoid additive effects.
• Bone Health Medications:
  • When used with medications that affect bone metabolism (e.g., corticosteroids), monitor bone density closely.

Reference: U.S. FDA; Clinical Pharmacology Reviews on PubMed

Frequently Asked Questions (FAQs)

Q: How does Letrozole work to treat breast cancer?
A: Letrozole inhibits the aromatase enzyme, reducing estrogen production. Lower estrogen levels decrease the growth stimulus for estrogen‑dependent breast cancer cells, thereby slowing tumor progression.

Q: Is Letrozole used only for breast cancer?
A: Primarily, yes. Letrozole is approved for advanced and early hormone receptor‑positive breast cancer in postmenopausal women. It is also used off‑label for ovulation induction in certain cases.

Q: How soon will I see an effect after starting Letrozole?
A: Some patients may notice a reduction in symptoms such as hot flashes within a few weeks, but the full therapeutic effect on tumor progression is usually evaluated over several months.

Q: What precautions should be taken regarding bone health?
A: Long‑term therapy with letrozole can decrease bone mineral density. Patients may be advised to take calcium and vitamin D supplements and undergo regular bone density monitoring.

Q: Can Letrozole be used during pregnancy?
A: No, letrozole is contraindicated during pregnancy due to its potential to cause fetal harm.

Q: What should I do if I miss a dose?
A: If you miss a dose, take it as soon as you remember. Do not double the dose to catch up. Consistency is key; consult your healthcare provider for any dosing adjustments.

Reference: U.S. FDA Femara Prescribing Information; NCCN Guidelines; PubMed

Where can I find additional clinical evidence and detailed information about Letrozole?

For further details on clinical studies, dosing guidelines, and safety monitoring, please refer to:

• U.S. Food and Drug Administration (FDA) Website: FDA.gov
• ClinicalTrials.gov: Search for letrozole studies (e.g., NCT00003250)
• PubMed: For peer‑reviewed research articles on letrozole in breast cancer (e.g., Lønning & Eikesdal, 2011)
• World Health Organization (WHO) Guidelines: On hormone therapy in breast cancer
• National Comprehensive Cancer Network (NCCN) Guidelines: For breast cancer treatment protocols

Reference: U.S. FDA; ClinicalTrials.gov; PubMed; NCCN; WHO

Final Thoughts

Letrozole (Femara®) is a well‑established aromatase inhibitor that plays a critical role in the management of hormone receptor‑positive breast cancer in postmenopausal women. By significantly reducing estrogen production, it helps to slow the growth of estrogen‑dependent tumors and improve patient outcomes. However, due to its potential impact on bone density, lipid profiles, and liver function, careful patient selection and monitoring are essential. Always consult your healthcare provider to ensure that letrozole is the appropriate treatment for your condition and to manage any potential risks or interactions.

Disclaimer: This guide is provided for educational purposes only and should not replace professional medical advice. Always consult with your healthcare provider before initiating or modifying any medication regimen.