Femara (letrozole) dosing, indications, interactions, adverse effects, and more

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Sections letrozole
Dosing & Uses
Interactions
Adverse Effects
Warnings
Pregnancy
Pharmacology
Administration
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Patient Handout
Formulary

Dosing & Uses

AdultPediatric

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

Interaction Checker

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Interactions Found

Contraindicated

Serious - Use Alternative

Significant - Monitor Closely

Minor

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>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

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

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.

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%

Oral Administration

May take with or without food

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Patient Handout

Formulary

FormularyPatient Discounts

Adding plans allows you to compare formulary status to other drugs in the same class.

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Adding plans allows you to:

View the formulary and any restrictions for each plan.
Manage and view all your plans together – even plans in different states.
Compare formulary status to other drugs in the same class.
Access your plan list on any device – mobile or desktop.

The above information is provided for general informational and educational purposes only. Individual plans may vary and formulary information changes. Contact the applicable plan provider for the most current information.

View explanations for tiers and restrictions

Tier	Description
1	This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
2	This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
3	This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
4	This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
5	This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
6	This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
NC	NOT COVERED – Drugs that are not covered by the plan.

Code	Definition
PA	Prior Authorization Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription.
QL	Quantity Limits Drugs that have quantity limits associated with each prescription. This restriction typically limits the quantity of the drug that will be covered.
ST	Step Therapy Drugs that have step therapy associated with each prescription. This restriction typically requires that certain criteria be met prior to approval for the prescription.
OR	Other Restrictions Drugs that have restrictions other than prior authorization, quantity limits, and step therapy associated with each prescription.

Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.

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Sections letrozole
Dosing & Uses
Interactions
Adverse Effects
Warnings
Pregnancy
Pharmacology
Administration
Images
Patient Handout
Formulary

letrozole (Rx)