What it does
Letrasole is a medication often used in cancer treatment.
Commonly used for: breast cancer, hormone-sensitive breast cancer
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Source: Food and Drugs Authority · fetched 2026-04-18 08:32:58 · updated 2026-09-25 04:00:08
About this medicine
Letrasole is a medication often used in cancer treatment.
What it treats
- breast cancer
- hormone-sensitive breast cancer
How it works
Letrasole works by lowering the amount of estrogen in the body, which can help slow or stop the growth of certain types of breast tumors that need estrogen to grow.
Who it's for
This medicine is typically prescribed for women who have had surgery for breast cancer and are at risk of the cancer returning.
AI-assisted summary grounded in BNF data - general information only, not medical advice. Always confirm with your pharmacist or doctor.
Clinical monograph: letrasole
Letrasole, also known as letrozole, is an aromatic anti-estrogen used primarily in hormone receptor-positive breast cancer treatment in postmenopausal women. It functions by inhibiting aromatase, an enzyme crucial for estrogen synthesis, thereby lowering estrogen levels in the body. This reduction in estrogen can slow or stop the growth of hormone-sensitive tumors.
Indications
- Hormone receptor-positive breast cancer in postmenopausal women
- Adjuvant treatment of early breast cancer
- Advanced breast cancer in postmenopausal women
Dosage
Children: Letrasole is not indicated for use in children. Refer to the BNF for Children for further information.
Adults: Refer to the BNF for specific adult dosing regimens based on the type and stage of breast cancer.
Mechanism of action
Letrozole selectively inhibits the aromatase enzyme, which is responsible for converting androgens into estrogens in peripheral tissues. By blocking this pathway, letrozole significantly decreases circulating estrogen levels, which is essential for the growth of certain breast cancers that rely on estrogen for proliferation.
Pharmacodynamics
Letrozole exhibits its pharmacological effects by inhibiting estrogen synthesis, leading to a decrease in estrogen-dependent tumor growth. The drug's effectiveness in reducing estrogen levels is directly correlated with its ability to inhibit aromatase, thereby contributing to lower rates of tumor recurrence and improved survival outcomes in patients with estrogen receptor-positive breast cancer.
Pharmacokinetics
Letrozole is well-absorbed following oral administration, with a bioavailability of approximately 99.9%. It is extensively metabolized in the liver, primarily by the cytochrome P450 enzyme CYP2A6, leading to several metabolites, although none are considered pharmacologically active. The elimination half-life of letrozole is around 2 days, and it is excreted mainly through urine as metabolites. Steady-state concentrations are reached within 2 to 6 weeks of continuous dosing.
Contra-indications
- Hypersensitivity to letrasole or any of its components
- Severe liver impairment
- Pregnancy
Adverse effects
- Nausea
- Vomiting
- Fatigue
- Headache
- Dizziness
- Hot flashes
- Hypertension
- Arthralgia
- Bone pain
Interactions
- Increased risk of toxicity when used with strong CYP3A4 inhibitors
- Reduced effectiveness when used with CYP3A4 inducers
Precautions
- Monitor liver function during treatment
- Use with caution in patients with a history of cardiovascular disease
- Assess bone health due to potential for bone density loss
Pregnancy
Letrasole is contraindicated in pregnancy due to the potential risk of fetal harm.
Breast-feeding
It is not known whether letrasole is excreted in human milk. Caution should be exercised when administering to nursing mothers.
Storage
Store in a cool, dry place, away from direct sunlight. Keep out of reach of children.
Formulations
- Tablets
AI-synthesized from BNF references - general information only, not a substitute for professional medical advice or the current BNF. Verify doses with a pharmacist.