letrozole: clinical use

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.

Tablet

Route: Oral

Strengths: 2.5 mg