letrozole: prescribing and clinical use
Focused clinical detail for use alongside current product information, local policy and patient-specific assessment.
letrozole: clinical details
Prescribing considerations
- Confirm postmenopausal endocrine status for licensed breast-cancer use; measure LH, FSH and/or oestradiol if uncertain.
- Assess fracture and osteoporosis risk before treatment and manage bone protection where appropriate.
- Carefully consider benefit and risk in severe renal impairment because evidence is limited.
- Use close supervision in severe hepatic impairment because systemic exposure and elimination half-life are increased.
- Review concurrent oestrogens, tamoxifen, other anti-oestrogens and relevant complementary products.
- Advise prompt reporting of tendon pain or swelling and assess for tendonitis or rupture.
Contraindications and cautions
- Hypersensitivity to letrozole or a listed excipient
- Premenopausal endocrine status for the selected licensed product
- Pregnancy
- Breastfeeding
- The selected product contains lactose and should not be used in specified rare hereditary disorders of galactose metabolism or absorption.
Monitoring
- Clinical response and disease status
- Bone mineral density before and during treatment, with follow-up where appropriate
- Blood pressure and cholesterol
- Tendon symptoms
- Clinical status in severe hepatic impairment
Clinical pharmacology
Letrozole competitively inhibits the haem component of aromatase cytochrome P450, suppressing oestrogen biosynthesis. Oral absorption is rapid and almost complete; food does not materially change overall exposure. It is metabolised mainly to an inactive carbinol metabolite, involving CYP3A4 and CYP2A6.
Formulation and product differences
- The selected Femara product is a dark-yellow, round film-coated tablet marked “FV” and “CG”.
- It contains lactose monohydrate and is essentially sodium-free.
- It should be kept in its original package, protected from moisture and stored below the product's stated maximum temperature.
letrozole preparations and strengths
Tablet
Route: Oral
Strengths: 2.5 mg
letrozole interactions
Tell the prescriber or pharmacist about all prescribed, over-the-counter and complementary products.
Tamoxifen
May substantially reduce letrozole concentrations and diminish its action; concurrent use should be avoided unless specifically directed by a specialist.
Other anti-oestrogens
May oppose or diminish letrozole's action and should generally not be combined with it.
Oestrogen-containing treatments, including HRT
Can reduce letrozole's effect and should not usually be taken concurrently.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.