Letrozole

Adjuvant treatment of hormone-receptor-positive early breast cancer in postmenopausal women; extended adjuvant treatment after five years of adjuvant tamoxifen. First-line treatment of hormone-receptor-positive or unknown locally advanced/metastatic breast cancer, and advanced disease progressing after antiestrogen therapy, are also labeled in postmenopausal women.

This profile reviews single-agent Femara labeling. Ovulation induction, ovarian suppression/premenopausal oncology and ribociclib/other combination products require separate authoritative regimens and are not supplied here. The label’s historical lack-of-combination-experience statement does not establish a current prohibition on all specialist combinations.

The full hepatic dosing section specifically identifies cirrhosis with severe dysfunction; the abbreviated highlights phrase is broader. Effects in noncirrhotic cancer patients with elevated bilirubin are undetermined. Do not invent dosing below CLcr 10 mL/min, a dialysis schedule or a pediatric/fertility regimen. An individualized missed-dose plan should prevent unsupervised extra doses.

Pregnancy and known hypersensitivity to letrozole or an excipient are contraindicated.

The selected current Femara label has no boxed warning. Its pregnancy contraindication and serious embryo-fetal and bone risks remain clinically important.

Reported effects include hot flashes, joint/muscle/bone pain, fatigue, headache, dizziness, sweating, edema and hypercholesterolemia. Fractures and osteoporosis are important long-term effects. Postmarketing reports include hepatitis, allergy/anaphylaxis, serious skin reactions, carpal tunnel and tendon disorders including rupture; frequencies/causality cannot be reliably established from spontaneous reports.

Concurrent tamoxifen reduced letrozole concentrations by about 38% in the cited study; clinical sequential use immediately after tamoxifen did not impair the demonstrated second-line effect. Cimetidine and warfarin studies found no clinically significant PK effect; this does not remove warfarin’s ordinary monitoring or prove safety of every combination.

CYP3A4/CYP2A6 contribute to metabolism and in-vitro CYP2A6/CYP2C19 inhibition has uncertain clinical significance. Review all medicines with the oncology team. Current combination-product indications and schedules are not inferred from the single-agent label’s historical clinical-experience wording.

Letrozole is contraindicated in pregnancy and can cause fetal harm; human postmarketing adverse outcomes and animal studies support concern without a precise human risk rate. Test before treatment if reproductive potential exists; effective contraception is advised during and at least three weeks after therapy. Human milk/infant/milk-production data are absent; avoid breastfeeding over the same interval. Animal data suggest possible fertility impairment in females and males.

Pediatric safety/effectiveness are unestablished; developmental animal findings are not a pediatric therapeutic protocol. Older postmenopausal patients were studied without an overall age-only efficacy/safety difference from younger patients, although individual sensitivity and comorbidities still require review.

No renal adjustment for CLcr at least 10 mL/min. Severe cirrhosis/Child-Pugh C studies showed approximately doubled exposure; the full dosing recommendation is 2.5 mg every other day for cirrhosis with severe dysfunction. Noncirrhotic elevated-bilirubin cancer exposure and lower-CLcr/dialysis dosing are not established by this label.

Letrozole competitively inhibits aromatase-mediated conversion of androgens to estrogens in peripheral/tumor tissues. It lowers estrone/estradiol in postmenopausal patients without demonstrated clinically relevant adrenal corticosteroid suppression at studied therapeutic exposures.

Oral absorption is rapid/complete and unaffected by food. Metabolism to an inactive carbinol metabolite followed by renal glucuronide excretion is the major clearance route; CYP3A4 and CYP2A6 participate. Terminal half-life is about two days and steady state after daily 2.5 mg takes roughly two to six weeks. Severe cirrhosis reduces clearance/increases exposure.

Assess response/recurrence or progression and confirm the prescribed duration. Consider BMD and cholesterol monitoring; review musculoskeletal/tendon symptoms, falls/fracture risks, fatigue and hepatic status. Avoid driving until individual effects are known. Discuss pregnancy testing, contraception, feeding and fertility as applicable. Do not substitute a fertility or combination regimen for this oncology prescription.

Seek medical/Poison Control assessment for excess dosing. Human overdose data are limited and do not establish a safe threshold or firm treatment protocol. The label includes older induced-emesis wording; this profile does not recommend home emesis. Supportive care and monitoring are clinician directed.

Product

Novartis Femara 2.5 mg

Route

Oral film-coated tablet

Appearance

Dark yellow, round, slightly biconvex; FV / CG

Package

HDPE bottle 30 · NDC 0078-0249-15

Selected Femara tablets contain 2.5 mg letrozole. Check inactive ingredients for allergy. Other manufacturers, liquid/compounded preparations, crushing/tube stability and combination co-packs are not reviewed.

Store at 20–25°C; excursions 15–30°C are permitted. Follow the safety-cap container, dispensing label and expiry. No independently verified compounded beyond-use date or opened-tablet stability protocol is supplied.