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Letrozole - Precautions and side effects

by egpat         12 Apr 2024

Letrozole is a well-known drug that is classified as an aromatase inhibitor, and letrozole is a non-steroidal aromatase inhibitor. This drug is indicated for the treatment of postmenopausal breast cancer. In postmenopausal women, the aromatase enzyme plays an important role in the synthesis of estrogens from androgens. So in postmenopausal women where estrogen levels are excessively increased, they may produce proliferation of breast tissue, resulting in estrogen-responsive breast cancer.

In such conditions, letrozole acts as an aromatase inhibitor, thereby inhibiting estrogen synthesis, so estrogen levels are reduced, resulting in decreased proliferation of breast cancer. That's why letrozole can be used as a first-line agent in the treatment of breast cancer in postmenopausal women.

This drug can also be used as an adjuvant along with tamoxifen in order to increase the efficacy of the treatment. Letrozole can also be used as an off-label for the induction of ovulation in women. Since letrozole inhibits estrogen synthesis, it can reduce the negative feedback mechanism so that it can increase the release of gonadotrophs from the anterior pituitary. So it can increase the release of follicle-stimulating hormone as well as luteinizing hormone.

These two hormones can act on the ovary; they can increase follicular growth as well as the phases of ovulation, so that ovulation is going to be increased in these patients. So letrozole can increase ovulation. That's why it can be used for the management of infertility, but this is one of the off-label purposes of this drug. So here in this article, let us discuss the important precautions and side effects of this drug.

Precautions for Letrozole

Letrozole is a non-steroidal aromatase inhibitor, and it can be used for breast cancer in post-menopausal women. This drug can also be used to induce ovulation in women, but it should not be given to pregnant women as it is teratogenic and can produce some fetal damage. Therefore, in pregnant women, this drug is contraindicated, or in women liable to become pregnant in a few months, this letrozole is contraindicated because of any risk of fetal damage in the near future. Similarly, this drug is not indicated for the treatment of breast cancer in premenopausal women, where this drug is ineffective.

Effect on bone mineral density

Another important precaution is that letrozole can reduce bone mineral density. So it can increase the risk of osteoporosis as well as the risk of fractures, particularly because it can produce lumbar spinal damage in between the L2 and L4 segments. This damage is more pronounced, resulting in back pain and bone pain in the patients. So during the long-term treatment with letrozole, the bone mineral density should be closely monitored in order to check for any development of hip and bone fractures.

Effects on cholesterol

Similarly, this drug can increase the deposition of cholesterol within the body. By increasing cholesterol levels, it can increase cardiovascular complications. So if the patient already has any risk factors for cardiovascular complications, this drug should be carefully given. And sometimes medications like statins are required to control the excessive cholesterol levels raised by letrozole.

Similarly, letrozole can increase liver impairment; liver functionalities may be reduced during the treatment with letrozole. In patients with any hepatic impairment, this drug should be carefully given, so in such patients, the dose of the drug should be reduced in order to avoid further liver impairment.

Similarly, this drug can increase the dizziness in the patients, resulting in some lightheadedness; it can also increase fatigue, so weakness is commonly observed with letrozole. Because of dizziness and fatigue, caution should be taken while driving vehicles or working with machinery because this drug can increase the risk of accidents due to dizziness and fatigue.

Side effects

Letrozole can produce a flushing and some vasodilatory responses, resulting in increased warmth and redness of the skin, and it can produce some back pain because of any bone fractures. It can also produce arthralgia, or joint pain.

Another important side of it is the dizziness and lightheadedness that can be produced by this drug, and hot flashes can be observed because of the hormonal response. It can also produce some headaches in patients. Another important side effect is edema because of the vasodilatory response.

It can also produce asthenia and a lack of energy in the patients, and finally, this drug can also produce bone fractures, which should be closely monitored. So these are the important side effects of this drug, letrozole, that are commonly observed in many of the patients.


So that's about the precautions and side effects of letrozole. It can increase the risk of bone fractures, it can increase cholesterol levels, and it can impair liver functionality. This drug should not be given to a pregnant woman or a woman liable to become pregnant within a few months because it produces some fetal damage. Dizziness, headache, asthenia, and edema are the important side effects produced by this drug.

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