Letrozole is a new generation of highly selective aromatase inhibitors, which is a synthetic benztriazole derivative. By inhibiting aromatase, estrogen levels can be reduced, thereby eliminating the stimulating effect of estrogen on tumor growth. In vivo, it is 150-250 times more active than the first-generation aromatase inhibitor ammoniumide. Because of its high selectivity, it does not affect glucocorticoids, corticosteroids and thyroid function, and large doses have no inhibitory effect on the secretion of adrenal corticosteroids, so it has a high therapeutic index.

Letrozole is primarily used in postmenopausal women with estrogen receptor (ER/ PR-positive) positive breast cancer. Breast cancer is related to estrogen, estrogen in pre-menopausal women mainly comes from the ovaries, after menopause is mainly converted by androgens into estrogen, and androgens into estrogen, mainly through an enzyme - aromatase conversion, and letrozole is by inhibiting this enzyme to achieve the effect of reducing estrogen. Simply put, Letrozole is a "gateway" drug that inhibits estrogen conversion in postmenopausal women.

Indication

Various preclinical studies have shown that letrozole has no potential toxicity, no mutagenesis and carcinogenic effect on all systems and target organs of the body, and the toxic side effects are small, well tolerated, and the anti-tumor effect is stronger than other aromatase inhibitors and anti-estrogen drugs. It is suitable for the treatment of advanced breast cancer in postmenopausal patients who have not responded to anti-estrogen therapy and for the treatment of early breast cancer.

Adverse reactions and side effects

Randomized trials showed that the incidence of possible drug-related adverse reactions in oral letrozole 2.5mg per day was 33%, significantly lower than 46% in the AG group. Most of the adverse reactions of letrozole were mild or moderate, with nausea (2% ~ 9%), headache (0% ~ 7%), bone pain (4% ~ 10%), hot flash (0% ~ 9%) and weight gain (2% ~ 8%) as the main manifestations. Other rare cases include constipation, diarrhea, itching, rash, joint pain, chest pain, abdominal pain, fatigue, insomnia, dizziness, edema, high blood pressure, irregular heartbeat, thrombosis, dyspnea, vaginal bleeding, etc. Most patients are well tolerated after taking letrozole, but the drug is toxic, and the side effects of letrozole mainly include:

1. Mental symptoms: fatigue, headache. Some patients have this symptom reaction at the beginning of taking it, but it is generally not obvious.

2. Malignant, abdominal pain, this symptom is relatively rare. Some patients have symptoms of constipation.

3. Skeletal muscle pain, joint pain. The incidence of this symptom is the highest, and many patients have such symptoms for about half a year.

4. Cough and chest pain, some patients will have dry cough and chest discomfort symptoms after 1 year of taking, which can be tolerated.