Letrozole Hexal: Uses, Dosage & Side Effects

What Is Letrozole Hexal and What Is It Used For?

Letrozole Hexal contains the active substance letrozole, a potent and highly selective third-generation non-steroidal aromatase inhibitor. Aromatase, also known as cytochrome P450 19A1 (CYP19A1), is the enzyme responsible for the final step in the biosynthesis of estrogens. It catalyzes the conversion of androgens (specifically androstenedione and testosterone) to estrogens (estrone and estradiol, respectively) through a process called aromatization. In postmenopausal women, the ovaries no longer produce significant amounts of estrogen, and the primary source of circulating estrogens shifts to peripheral tissues such as adipose tissue, muscle, liver, and the breast itself, where aromatase converts adrenal androgens into estrogens.

Letrozole binds competitively to the heme group of the aromatase enzyme, effectively blocking its activity. This results in a dramatic reduction of circulating estrogen levels. In clinical pharmacological studies, letrozole 2.5 mg daily reduced plasma estradiol, estrone, and estrone sulfate concentrations by approximately 95–99% from baseline in postmenopausal women. This profound estrogen suppression is central to the drug’s anticancer mechanism: approximately 75% of breast cancers express estrogen receptors (ER+) and/or progesterone receptors (PR+), meaning that their growth is driven by estrogen signaling. By removing the estrogenic stimulus, letrozole causes these cancer cells to stop proliferating and, in many cases, to undergo apoptosis (programmed cell death).

Letrozole Hexal is a generic formulation manufactured by Hexal AG, a subsidiary of the Sandoz Group (part of Novartis). It has been demonstrated to be bioequivalent to the originator product Femara, meaning it delivers the same amount of active substance to the bloodstream at the same rate and to the same extent. Generic letrozole formulations undergo rigorous regulatory review by the European Medicines Agency (EMA) and national authorities to ensure pharmaceutical quality, safety, and efficacy equivalent to the reference product.

The therapeutic indications for Letrozole Hexal encompass several clinical settings in postmenopausal women with hormone receptor-positive breast cancer:

• Adjuvant treatment of early breast cancer: After primary surgical treatment (lumpectomy or mastectomy), letrozole is given for up to 5 years to reduce the risk of cancer recurrence. The landmark BIG 1-98 trial, which enrolled over 8,000 postmenopausal women with HR+ early breast cancer, demonstrated that letrozole was superior to tamoxifen as initial adjuvant therapy, with a 19% relative risk reduction in disease-free survival events (hazard ratio 0.81; 95% CI 0.70–0.93; p=0.003). Specific benefits included significant reductions in distant metastases (hazard ratio 0.73), contralateral breast cancer, and overall breast cancer events.
• Extended adjuvant treatment: After completing 5 years of adjuvant tamoxifen therapy, letrozole may be given for an additional 5 years to further reduce the risk of late recurrence. The MA.17 trial demonstrated that extended adjuvant letrozole significantly improved disease-free survival compared to placebo after 5 years of tamoxifen (hazard ratio 0.58; p<0.001), with particular benefit in reducing distant metastases.
• First-line treatment of advanced or metastatic breast cancer: In postmenopausal women with HR+ advanced breast cancer, letrozole has shown superior efficacy to tamoxifen as first-line endocrine therapy, with significantly longer time to disease progression (median 9.4 months vs 6.0 months; p<0.0001) and higher objective response rates.
• Treatment of advanced breast cancer after anti-estrogen therapy failure: For women whose disease has progressed on prior anti-estrogen treatment (typically tamoxifen), letrozole offers an effective second-line endocrine therapy option.

Letrozole is included on the World Health Organization (WHO) Model List of Essential Medicines, recognizing its critical importance in global cancer care. It has become one of the most widely prescribed endocrine therapies for breast cancer worldwide and represents a cornerstone of modern breast cancer management. The third-generation aromatase inhibitors (letrozole, anastrozole, and exemestane) have largely replaced tamoxifen as the preferred initial adjuvant endocrine therapy for postmenopausal women with HR+ breast cancer, based on demonstrated superior efficacy in reducing recurrence risk.

What Should You Know Before Taking Letrozole Hexal?

Contraindications

Letrozole Hexal must not be used in the following situations:

• Premenopausal endocrine status: Letrozole is effective only in women whose ovaries are no longer producing estrogen. In premenopausal women, aromatase inhibition leads to a compensatory increase in gonadotropin secretion (FSH and LH), which stimulates the ovaries to produce more androgens and potentially more estrogens through alternative pathways. Menopausal status must be confirmed before starting treatment.
• Pregnancy and breastfeeding: Letrozole is classified as a teratogen and is contraindicated during pregnancy. Animal studies have shown embryotoxicity and teratogenicity at doses similar to human therapeutic doses. Women of childbearing potential (including those undergoing ovarian suppression) must use adequate contraception during treatment and for at least 3 weeks after the last dose. Letrozole must not be used during breastfeeding as it is not known whether it is excreted in human breast milk.
• Hypersensitivity: Do not use if you are allergic to letrozole or any of the excipients (inactive ingredients) in the tablet formulation, which include lactose monohydrate, microcrystalline cellulose, maize starch, sodium starch glycolate, colloidal anhydrous silite, and magnesium stearate, with the film coating containing hypromellose, macrogol, and titanium dioxide.

Warnings and Precautions

Before starting Letrozole Hexal, discuss the following with your healthcare provider:

• Bone health and osteoporosis: Letrozole causes a significant decrease in bone mineral density due to profound estrogen depletion. In the BIG 1-98 trial, the incidence of bone fractures was higher in the letrozole group compared to tamoxifen (9.3% vs 6.5%). The incidence of osteoporosis was also higher (5.1% vs 2.7%). Baseline and periodic bone mineral density assessments are recommended, and treatment with bone-protective agents (bisphosphonates such as zoledronic acid, or denosumab) should be considered for patients with T-scores below -2.0 or those with additional risk factors for fractures.
• Cardiovascular risk: Long-term estrogen depletion may unfavorably affect lipid profiles. In clinical trials, letrozole was associated with a higher incidence of hypercholesterolemia compared to tamoxifen (52.3% vs 28.6%). Lipid levels should be monitored, and cardiovascular risk factors should be managed according to established guidelines. However, letrozole carries a lower risk of thromboembolic events (deep vein thrombosis, pulmonary embolism) compared to tamoxifen.
• Hepatic impairment: Letrozole is extensively metabolized by the liver. In patients with severe hepatic impairment (Child-Pugh C), the systemic exposure to letrozole is approximately doubled. Letrozole should be used with caution in these patients and dose adjustment may be necessary. No dose adjustment is required for patients with mild to moderate hepatic impairment.
• Renal impairment: No dose adjustment is required for patients with renal impairment (creatinine clearance ≥10 mL/min). The pharmacokinetics of letrozole are not significantly altered in patients with moderate to severe renal impairment, although no studies have been conducted in patients with creatinine clearance below 10 mL/min.
• Fatigue and dizziness: Letrozole may cause fatigue, dizziness, and somnolence. Patients experiencing these side effects should not drive or operate machinery until they know how letrozole affects them. These symptoms are usually mild and may diminish with continued treatment.

Pregnancy and Breastfeeding

Letrozole is absolutely contraindicated during pregnancy. It belongs to FDA pregnancy category X, meaning that studies in animals or humans have demonstrated fetal abnormalities, and the risk of using the drug clearly outweighs any possible benefit. Animal reproductive studies have shown that letrozole causes post-implantation loss, increased resorptions, decreased numbers of live fetuses, and fetal abnormalities including incomplete ossification and skeletal malformations at doses comparable to or lower than human therapeutic doses.

Women who are or may become pregnant must not take letrozole. If a patient becomes pregnant while taking letrozole, the medication should be discontinued immediately and the patient should be counseled about the potential risk to the fetus. Women of childbearing potential, including those whose menopausal status is uncertain, should have a pregnancy test before starting treatment and should use effective contraception during treatment and for at least 3 weeks after stopping letrozole.

It is not known whether letrozole is excreted in human breast milk. Because of the potential for serious adverse reactions in nursing infants, breastfeeding is contraindicated during letrozole treatment and for at least 3 weeks after the last dose.

How Does Letrozole Hexal Interact with Other Drugs?

Letrozole is metabolized in the liver primarily by the cytochrome P450 enzymes CYP3A4 and CYP2A6. Understanding potential drug interactions is important to ensure optimal therapeutic benefit and to avoid adverse effects. The following sections outline the known and potential drug interactions with letrozole.

Major Interactions

Minor Interactions

In vitro studies have shown that letrozole inhibits CYP2A6 and moderately inhibits CYP2C19, but the clinical significance of these interactions at therapeutic doses appears to be limited. Importantly, letrozole does not significantly inhibit CYP1A2, CYP2D6, CYP2C9, CYP2E1, or CYP3A4 at clinically relevant concentrations, which means it has a relatively low potential for pharmacokinetic interactions with most co-administered drugs.

In advanced breast cancer, letrozole is increasingly being used in combination with CDK4/6 inhibitors (palbociclib, ribociclib, or abemaciclib) and/or PI3K inhibitors (alpelisib) as standard of care. These combinations have demonstrated significant improvements in progression-free survival in multiple phase III trials. When using these combinations, the prescribing information for each agent should be followed, with particular attention to the specific drug interaction profiles of the partner agents.

What Is the Correct Dosage of Letrozole Hexal?

Adults (Postmenopausal Women)

Children and Adolescents

Letrozole Hexal is not indicated for use in children or adolescents. The safety and efficacy of letrozole in pediatric populations have not been established. Letrozole is specifically designed for postmenopausal women and should not be used in pre-pubertal or adolescent patients. There are no approved pediatric dosing recommendations.

Elderly Patients

No dose adjustment is required for elderly patients. In the pivotal BIG 1-98 clinical trial, approximately 36% of patients were 65 years of age or older, and no overall differences in safety or efficacy were observed between older and younger patients. Letrozole has been well studied in elderly postmenopausal populations, and the 2.5 mg once-daily dose is appropriate regardless of age. However, as with any medication in elderly patients, individual tolerability and the presence of comorbid conditions should be taken into account, particularly regarding bone health and cardiovascular risk.

Missed Dose

If you miss a dose of Letrozole Hexal, take it as soon as you remember, provided it is not nearly time for your next scheduled dose. If it is almost time for the next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. Because letrozole has a long elimination half-life (approximately 2 days), missing a single dose is unlikely to significantly affect overall estrogen suppression. However, consistent daily dosing is important for maintaining optimal drug levels and therapeutic efficacy. If you frequently forget to take your medication, consider setting a daily reminder or using a pill organizer.

Overdose

There is limited clinical experience with overdosage of letrozole. Isolated cases of letrozole overdose have been reported without serious sequelae. In clinical trials, the highest single dose studied was 30 mg (12 times the recommended dose), which was generally well tolerated. There is no specific antidote for letrozole overdose. In the event of an overdose, management should be symptomatic and supportive. General supportive care, including frequent monitoring of vital signs and close observation of the patient, is recommended. Given that letrozole has moderate protein binding (~60%) and a relatively small volume of distribution, hemodialysis may be considered, although its efficacy in letrozole removal has not been studied. Contact your local poison control center or seek immediate medical attention if overdose is suspected.

What Are the Side Effects of Letrozole Hexal?

The side effects of Letrozole Hexal are primarily a consequence of its potent estrogen-lowering action. Because estrogen plays important roles throughout the body beyond breast cancer biology — including in bone metabolism, cardiovascular function, lipid regulation, and thermoregulation — profound estrogen depletion can lead to a range of adverse effects. The following lists categorize side effects by their reported frequency in clinical trials and post-marketing surveillance.

It is important to understand that many of the common side effects of letrozole, such as hot flashes, joint pain, and bone loss, are directly related to the intended pharmacological effect of reducing estrogen levels. These effects are generally manageable and should be weighed against the significant survival benefits of adjuvant endocrine therapy. Studies have shown that adherence to the full prescribed course of letrozole treatment is associated with better cancer outcomes, so patients are strongly encouraged to discuss bothersome side effects with their oncologist rather than stopping treatment on their own.

Joint pain and stiffness (often called “aromatase inhibitor-associated musculoskeletal symptoms” or AIMSS) are among the most commonly reported reasons for treatment discontinuation. Several strategies have been shown to help manage these symptoms, including regular physical exercise (particularly weight-bearing and flexibility exercises), acupuncture, switching between aromatase inhibitor agents, and in some cases short-term analgesic therapy. Clinical research has demonstrated that regular physical activity not only helps manage joint symptoms but may also improve overall cancer outcomes.

How Should You Store Letrozole Hexal?

Proper storage of Letrozole Hexal is essential to maintain the quality, safety, and efficacy of the medication throughout its shelf life. The film-coated tablets should be stored at a controlled room temperature, not exceeding 30°C (86°F). The medication should be kept in its original blister packaging or container to protect it from moisture and light, both of which can potentially degrade the active ingredient over time.

Keep Letrozole Hexal out of the reach and sight of children. The medication should be stored in a secure location, as accidental ingestion by children or other household members could be harmful. Do not store the tablets in the bathroom or other areas with high humidity, as moisture can affect the stability of the film coating and the active ingredient.

Do not use Letrozole Hexal after the expiry date (EXP) stated on the blister pack and the outer carton. The expiry date refers to the last day of that month. If tablets appear discolored, damaged, or otherwise different from their usual appearance, do not use them and consult your pharmacist.

Do not dispose of Letrozole Hexal via household waste or wastewater. As a hormone-modifying medication, letrozole may pose environmental risks if released into water systems. Return any unused or expired medication to your pharmacist for safe disposal in accordance with local regulations.

What Does Letrozole Hexal Contain?

Active ingredient: Each film-coated tablet contains 2.5 mg of letrozole. Letrozole is a non-steroidal aromatase inhibitor with the chemical name 4,4′-(1H-1,2,4-triazol-1-ylmethylene)dibenzonitrile. It has a molecular formula of C₁₇H₁₁N₅ and a molecular weight of 285.31 g/mol. Letrozole is a white to yellowish crystalline powder that is practically insoluble in water, freely soluble in dichloromethane, slightly soluble in ethanol, and sparingly soluble in acetonitrile.

Inactive ingredients (excipients):

• Tablet core: Lactose monohydrate, microcrystalline cellulose, maize starch (corn starch), sodium starch glycolate (Type A), colloidal anhydrous silica (silicon dioxide), magnesium stearate
• Film coating: Hypromellose (hydroxypropyl methylcellulose), macrogol (polyethylene glycol), titanium dioxide (E171)

Appearance: Letrozole Hexal 2.5 mg tablets are round, slightly biconvex, yellow film-coated tablets. They are typically supplied in blister packs of 30, 60, or 100 tablets in a cardboard outer carton. Pack sizes may vary by country and market.