Letrozole 5 mg

Introduction

An oral drug called letrozole 5 mg is used to treat postmenopausal women with hormone receptor-positive breast cancer. It is also widely used off-label to treat female infertility, especially in women with polycystic ovary syndrome (PCOS). Belonging to the class of aromatase inhibitors, works by reducing estrogen levels in the body, which is vital in slowing or stopping the growth of estrogen-dependent cancers and in stimulating ovulation.

Letrozole is typically available in 2.5 mg tablets, but in some therapeutic scenarios—especially fertility protocols—a higher dosage like 5 mg may be prescribed by a healthcare provider.

What is Letrozole?

Letrozole is a non-steroidal aromatase inhibitor. It blocks the enzyme aromatase, which the body uses to convert androgens (like testosterone) into estrogen. By reducing estrogen levels, Letrozole limits the stimulation of estrogen-sensitive tumors and encourages ovulation in anovulatory women.

Brand Names and Composition

• Generic Name: Letrozole

• Strength: 5 mg

• Common Brand Names: Femara (standardly in 2.5 mg)

• Form: Oral tablet

• Route of Administration: Oral

• Therapeutic Class: Antineoplastic agent (Breast Cancer) / Ovulation Inducer

Indications

1. Breast Cancer (Hormone Receptor-Positive)

Letrozole is approved for the following cancer-related indications:

• Postmenopausal women with hormone receptor-positive early breast cancer receiving adjuvant therapy

• After five years of tamoxifen therapy, prolonged adjuvant treatment

• First-line treatment for postmenopausal women with advanced or metastatic breast cancer

• Treatment of advanced breast cancer following a recurrence or advancement of the disease

2. Female Infertility (Off-Label Use)

Letrozole is increasingly used in:

• Ovulation induction in women with PCOS

• Unexplained infertility

• As an alternative to clomiphene citrate

• Frozen embryo transfer (FET) cycles

How Letrozole 5 mg Works

In Breast Cancer:

• Letrozole blocks aromatase, the enzyme responsible for the conversion of androgens to estrogens.

• Many breast cancers grow because of estrogen.

• Lower estrogen slows or stops tumor growth.

In Infertility Treatment:

• Letrozole lowers estrogen temporarily, which triggers the release of follicle-stimulating hormone (FSH) from the pituitary gland.

• FSH promotes ovulation by inducing the ovaries to generate follicles.

Dosage and Administration

For Breast Cancer:

• Standard Dose: 2.5 mg once daily

• A standard regimen is to take 5 mg every day for 5 days, usually from cycle day 3 to day 7.

For Infertility (Off-Label Use):

• Letrozole 5 mg daily for 5 days, usually from cycle day 3 to day 7, is a common protocol.

• It may be adjusted to 7.5 mg in resistant cases.

• Ultrasound monitoring is used to check for follicular development.

Note: Dosage must always be determined and supervised by a healthcare professional.

Pharmacokinetics

• Absorption: Rapid after oral administration

• Half-life: Approximately 2 days

• Metabolism: Hepatic, primarily via CYP3A4 and CYP2A6 enzymes

• Excretion: Urine (major route)

This long half-life allows once-daily dosing.

Benefits of Letrozole 5 mg

In Cancer Therapy:

• Proven efficacy in reducing recurrence risk in hormone-receptor positive breast cancer

• Effective as both first-line and second-line therapy

• Oral medication – easy to administer

• Fewer estrogenic side effects compared to tamoxifen

In Fertility Treatment:

• Effective ovulation inducer in PCOS patients

• Lower risk of multiple pregnancies than clomiphene

• A shorter half-life means fewer side effects

• Promotes a more natural endometrial lining than other agents

Side Effects

Common Side Effects:

• Hot flashes

• Joint pain or stiffness

• Fatigue or tiredness

• Night sweats

• Nausea

• Dizziness

Less Common Side Effects:

• Vaginal dryness

• Bone thinning (osteoporosis with long-term use)

• Headache

• Insomnia

• Weight gain

In Fertility Use:

• Mood swings

• Breast tenderness

• Mild bloating

• Ovarian cyst formation (rare)

Most side effects are dose-dependent and transient.

Contraindications

• Pregnancy: Category X: Because of the teratogenic consequences, do not use in pregnant women.

• Breast cancer in premenopausal women, unless recommended for reproductive reasons

• Severe liver disease

• Hypersensitivity to or any of its ingredients is known

Precautions and Monitoring

• Bone health monitoring for long-term use in cancer patients (risk of osteoporosis)

• Regular hormone level monitoring in fertility protocols

• Use barrier contraception during treatment if used off-label in women of reproductive age outside fertility protocols

• Patients with a history of cardiovascular disease should exercise caution.

Drug Interactions

Letrozole may interact with:

• Tamoxifen – may reduce effectiveness

• Estrogen-containing drugs – counteract mechanism

• CYP3A4 inhibitors/inducers – may affect Letrozole metabolism

Avoid combining with hormone replacement therapy (HRT).

Letrozole vs. Other Drugs

Use in Special Populations

Pregnancy:

• Absolutely contraindicated unless being used specifically in fertility treatments under medical supervision.

• Must be avoided during pregnancy due to risk of fetal harm.

Lactation:

• Not recommended; it’s unknown whether it passes into breast milk.

Geriatrics:

• Safe under monitoring; used in elderly women with breast cancer.

Children:

• Not indicated.

Patient Counseling Tips

• Take Letrozole at the same time daily

• May be taken with or without food

• Use non-hormonal contraception if applicable

• Report symptoms like bone pain, unusual bleeding, or severe dizziness

• Don’t use other estrogen-containing products unless directed

Storage and Handling

• Store at room temperature (15–30°C / 59–86°F)

• Protect from moisture and light

• Keep out of reach of children

• Do not use after expiration date

Letrozole in Fertility Clinics

Letrozole has gained popularity in reproductive medicine due to:

• Better endometrial thickness vs. clomiphene

• Higher pregnancy rates in some studies

• Use in ovulation induction and superovulation protocols

• Compatible with intrauterine insemination (IUI) cycles

Clinical Studies and Evidence

• Breast Cancer Trials: Letrozole has demonstrated superior disease-free survival in several trials like BIG 1-98.

• Fertility Studies: Several randomized controlled trials show superiority over clomiphene in inducing ovulation in PCOS patients with fewer side effects.

Conclusion

Letrozole 5 mg is a powerful and versatile medication with applications in both oncology and reproductive medicine. It plays a crucial role in the treatment of hormone-dependent breast cancer, as well as a popular off-label fertility treatment for women with ovulatory dysfunction.

When used under medical supervision, Letrozole is a safe, effective, and well-tolerated option. Whether you’re undergoing cancer treatment or working towards conception, Letrozole offers proven efficacy and life-changing outcomes.