Letrozole Tablets (Femara) are a non-steroidal aromatase inhibitor. By inhibiting the synthesis of estrogen in the body, it effectively suppresses tumor growth. Like all anticancer drugs, letrozole may also cause a series of side effects during treatment, some of which may even seriously affect the patient’s health.

What Are the Side Effects of Letrozole Tablets (Femara)?

Vasomotor Symptoms

Hot flashes and night sweats are among the most common adverse reactions of letrozole.

In clinical trials, approximately 30% to 50% of patients reported hot flashes, which are more common in adjuvant therapy and extended adjuvant therapy.

Musculoskeletal System Reactions

Joint pain and muscle pain are typical side effects of letrozole, with an incidence of approximately 20% to 25%.

Some patients may experience arthritis, bone pain, or back pain, which may affect daily life in severe cases.

General Discomfort

General symptoms such as fatigue, weakness, and edema are also relatively common, with an incidence ranging from 10% to 20%.

Some patients may experience weight gain or weight loss.

Metabolic Abnormalities

Letrozole may cause elevated blood lipids, especially increased total cholesterol levels.

In adjuvant therapy studies, approximately half of the patients developed hypercholesterolemia, requiring regular monitoring.

Serious Side Effects of Letrozole Tablets (Femara) That Require Vigilance

Decreased Bone Mineral Density and Fracture Risk

Letrozole can significantly reduce bone mineral density, increasing the risk of osteoporosis and fractures.

It is recommended to conduct regular bone mineral density tests during treatment.

If there is a risk of osteoporosis, bisphosphonate drugs may be considered for prevention or treatment.

Risk of Cardiovascular Events

Although uncommon, letrozole may increase the risk of cardiovascular events such as myocardial infarction, angina pectoris, and heart failure.

Patients should seek immediate medical attention if they experience symptoms such as chest pain, shortness of breath, or palpitations.

Abnormal Liver Function

In patients with severe hepatic impairment (e.g., cirrhosis), the plasma concentration of letrozole may increase significantly, requiring dosage adjustment (e.g., administration once every other day).

Liver function should be checked regularly during treatment.

Embryo-Fetal Toxicity

Letrozole has confirmed toxicity to the fetus and is contraindicated in pregnant women.

Women of childbearing potential must undergo a pregnancy test before taking the drug to rule out pregnancy, and use effective contraceptive measures during treatment and for at least 3 weeks after discontinuing the drug.

Rare but Severe Skin Reactions

A small number of patients may experience severe skin adverse reactions such as angioedema, toxic epidermal necrolysis, and erythema multiforme. Once these reactions occur, the drug should be discontinued immediately and medical attention sought.

Precautions for Administration of Letrozole Tablets (Femara)

Pre-Administration Evaluation

Confirm that the patient is in the postmenopausal state.

Test the hormone receptor status (ER/PgR).

Evaluate liver and renal function; dose reduction is required for patients with severe hepatic impairment.

Rule out pregnancy in women of childbearing potential.

Monitoring During Treatment

Conduct regular bone mineral density tests, especially for patients on long-term treatment.

Monitor blood lipid levels and administer lipid-lowering treatment if necessary.

Be alert to symptoms such as fatigue and dizziness, and avoid driving or operating machinery.

Patients on long-term treatment should undergo regular evaluation of cardiovascular health.