Letrozole

Trade Names:
Femara
- Tablets 2.5 mg

Pharmacology

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A nonsteroidal, competitive inhibitor of the aromatase enzyme system; inhibits the conversion of androgens to estrogens.

Pharmacokinetics

Absorption

Rapidly and completely absorbed. Food does not affect absorption. Steady state reached in 2 to 6 wk.

Distribution

Weakly protein bound. Vd is approximately 1.9 L/kg.

Metabolism

Slowly metabolized (CYP3A4, CYP2A6) to inactive metabolites.

Elimination

Renal excretion of inactive metabolites is major pathway of Cl; 6% of dose recovered as unchanged letrozole. Elimination t _½ is approximately 2 days.

Special Populations

No change in letrozole steady-state plasma concentrations noted in patients with moderate renal function impairment (CrCl, 20 to 50 mL/min).

AUC was 37% higher in patients with mild to moderate hepatic function impairment (Child-Pugh class A and B). AUC increased 2-fold and systemic Cl reduced 47% in patients with severe hepatic function impairment (Child-Pugh class C).

Indications and Usage

Extended adjuvant treatment of early breast cancer in postmenopausal women who have received 5 yr of adjuvant tamoxifen therapy; first-line treatment of postmenopausal women with hormone receptor-positive or hormone receptor-unknown locally advanced or metastatic cancer; advanced breast cancer in postmenopausal women with disease progression following antiestrogen therapy; adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer.

Unlabeled Uses

For ovulation stimulation to improve chances of pregnancy.

Contraindications

Standard considerations.

Dosage and Administration

PO 2.5 mg once daily without regard to meals.

PO Reduce dosage in patients with cirrhosis and severe hepatic function impairment 50% (2.5 mg every other day).

Storage/Stability

Store tablets at controlled room temperature (59° to 86°F).

Drug Interactions

Plasma concentrations of letrozole may be decreased.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Hypertension (8%); angina, coronary heart disease, hemiparesis, hemorrhagic or thrombotic strokes, MI, myocardial ischemia, portal vein thrombosis, pulmonary edema, thrombophlebitis, transient ischemic attacks, venous thrombosis (2% or less).

CNS

Asthenia (34%); headache (20%); dizziness (14%); fatigue (13%); insomnia (7%); weakness (6%); somnolence (3%); anxiety, depression, vertigo (less than 5%).

Dermatologic

Hot flushes (50%); increased sweating (24%); night sweats (14%); rash (5%); alopecia (less than 5%); pruritus (2%).

EENT

Blurred vision (postmarketing).

GI

Nausea (17%); constipation (11%); diarrhea (8%); vomiting (7%); abdominal pain (6%); anorexia, dyspepsia (4%).

Genitourinary

Breast pain (7%); UTI (6%); renal disorder, vaginal hemorrhage, vulvovaginal dryness (5%).

Hepatic

Increased hepatic enzymes (postmarketing).

Lymphatic

Postmastectomy lymphedema (7%).

Metabolic-Nutritional

Hypercholesterolemia (16%); increased weight (11%); decreased weight (7%); hypercalcemia (less than 5%).

Musculoskeletal

Arthralgia, bone pain (22%); back pain (18%); limb pain (10%); arthritis, myalgia (7%); fracture (less than 5%); osteoporosis (2%).

Respiratory

Dyspnea (18%); cough (13%); chest wall pain (6%).

Miscellaneous

Edema (18%); chest pain (8%); infections/infestations (7%); influenza (6%); pain (5%); pleural effusion (less than 5%); second malignancies (2%).

Precautions

Pregnancy

Category D .

Lactation

Undetermined.

Children

Safety and efficacy in children not established.

Hepatic Function

Dose reduction recommended in patients with cirrhosis and/or severe hepatic function impairment.

Hazardous Tasks

May cause drowsiness, fatigue, and/or dizziness.

Overdosage

Symptoms

Limited data available.

Patient Information

• Review dosing schedule with patient.
• Advise patient that medication can be taken without regard to meals, but to take with food if stomach upset occurs.
• Advise patient that if a dose is missed to take it as soon as possible. If close to next scheduled dose, skip the missed dose and take the next dose at the scheduled time. Caution patient not to double the dose to catch up.
• Instruct patient to report persistent or intolerable adverse reactions to health care provider.
• Caution patient that drug may cause drowsiness, fatigue, and/or dizziness and to use caution while driving or performing other tasks requiring mental alertness or coordination until tolerance is determined.

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