Dosing & Uses
Dosage Forms & Strengths
tablet
- 2.5mg
Breast Cancer
Adjuvant treatment of early breast cancer
- Postmenopausal women with hormone receptor positive early breast cancer
- 2.5 mg PO qDay
Extended adjuvant treatment of early breast cancer
- Postmenopausal women, who have received 5 yr of adjuvant tamoxifen therapy
- 2.5 mg PO qDay
First and second-line treatment of advanced breast cancer
- Postmenopausal women with hormone receptor positive or unknown, locally advanced or metastatic breast cancer
- Also indicated for treatment of advanced breast cancer in postmenopausal women with disease progression following antiestrogen therapy
- 2.5 mg PO qDay; continue until tumor progression is evident
Dosing Considerations
Effectiveness of letrozole in extended adjuvant treatment of early breast cancer is based on an analysis of disease-free survival in patients treated for a median of 60 months
Dosage Modifications
Renal impairment
- Mild-to-moderate (CrCl ≥30 mL/min): No dose adjustment necessary
- Severe (CrCl ≥10 to <30 mL/min): No dose adjustment necessary
Hepatic impairment
- Mild-to-moderate: No dose adjustment necessary
- Patients with cirrhosis and severe hepatic dysfunction: Reduce dose by 50% (ie, 2.5 mg every other day)
- Noncirrhotic patients with elevated bilirubin levels have not been studied
Ovarian Epithelial Cancer (Off-label)
2.5 mg PO qDay
Safety and efficacy not established
Interactions
Interaction Checker
No Results
Contraindicated
Serious - Use Alternative
Significant - Monitor Closely
Minor
Adverse 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 to drug or excipients
Pregnancy, premenopausal women
Cautions
Use caution in liver impairment; administer a low dose to patients with hepatic impairment; effect of hepatic impairment on drug exposure in cancer patients with elevated bilirubin levels not determined
Decreases in bone mineral density may occur; consider bone mineral density monitoring; increased risk of osteoporosis
May cause dizziness, somnolence and fatigue; exercise caution when operating machinery
May increase total serum cholesterol; consider cholesterol monitoring
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 & Lactation
Pregnancy
Based on post-marketing reports, findings from animal studies and mechanism of action, therapy can cause fetal harm and is contraindicated for use in pregnant women; in post-marketing reports, use during pregnancy resulted in cases of spontaneous abortions and congenital birth defects; however, data are insufficient to inform a drug-associated risk
Contraception
- Advise females of reproductive potential to use effective contraception during treatment and for at least 3 weeks after last dose
Infertility
- Therapy may impair fertility in females and males of reproductive potential
Lactation
Not known if therapy is present in human milk; there are no data on effects on breastfed infant or milk production; exposure of lactating rats to drug was associated with impaired reproductive performance of male offspring; because of potential for serious adverse reactions in breastfed infants, advise lactating women not to breastfeed while receiving therapy and for at least 3 weeks after last dose
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
Mechanism of Action
Aromatase inhibitor - blocks conversion of androgens to estrogens by binding to the heme group of aromatase enzyme, which in turn inhibits its activity
Distribution
Vd: 1.9 L/kg
Metabolism
Metabolites: 4,4'-methanol-bisbenzonitrile via CYP3A4 and 2A6 activity
Enzymes inhibited: Aromatase
Elimination
Half-life: 2 days
Excretion: Urine 90%
Administration
Oral Administration
May take with or without food
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Patient Handout
Formulary
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