Dosing and uses of Femara (letrozole)
Adult dosage forms and strengths
tablet
- 2.5mg
Breast Cancer
2.5 PO qDay, until tumor progression evident
Ovarian Epithelial Cancer (Off-label)
2.5 mg PO qDay
Other Indications & Uses
Adjuvant treatment of postmenopausal, hormone receptor positive, early breast cancer
Extended adjuvant treatment of early breast cancer in post-menopausal women after 5 years of adjuvant tamoxifen
First and second-line treatment of postmenopausal women with hormone receptor positive or unknown advanced breast cancer
Off-label: ovulation induction
Pediatric dosage forms and strengths
Safety and efficacy not established
Femara (letrozole) adverse (side) effects
>10%
Diaphoresis (24%)
Bone pain (22%)
Hot flashes (19%)
Back pain (18%)
Dyspnea (18%)
Nausea (17%)
Night sweats (14%)
Cough (13%)
Fatigue (13%)
1-10%
Constipation (10%)
Hypertension (8%)
Chest pain (8%)
Diarrhea (8%)
Decr wt (7%)
Edema (7%)
Breast pain (7%)
Bone fractures (6%)
UTI (6%)
Hypercalcemia (5%)
Headache (4%)
Weakness (4%)
Vomiting (3%)
Osteoporosis (2%)
<1%
Blurred vision
Increased hepatic enzyme levels
Postmarketing Reports
Blurred vision
Increased hepatic enzymes
Hepatitis
Angioedema
Anaphylactic reactions
Toxic epidermal necrolysis
Erythema multiforme
Carpal tunnel syndrome
Trigger finger
Warnings
Contraindications
Hypersensitivity
Pregnancy, premenopausal women
Cautions
Liver impairment
Incr risk of osteoporosis
Avoid concomitant estrogens
Risk of birth defects if given to pregnant women
- Used off-label to induce ovulation
- Health Canada & Novartis Canada warned against such use
Pregnancy and lactation
Pregnancy category: d
Lactation: not known if excreted in breast milk (for post-menopausal women)
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Femara (letrozole)
Mechanism of action
Aromatase inhibitor - blocks conversion of adrostenedione to estrone
Distribution
Vd: 1.9 L/kg
Metabolism
Metabolites: 4,4'-methanol-bisbenzonitrile
Enzymes inhibited: Aromatase
Elimination
Half-life: 2 days
Excretion: Urine 90%
