Nurses Compass
Drug Guide
Letrozole
Classification
Therapeutic: Antineoplastic agent (hormone therapy)
Pharmacological: Aromatase inhibitor
FDA Approved Indications
- Adjuvant treatment of hormone receptor-positive early breast cancer in postmenopausal women
- Treatment of hormone receptor-positive metastatic breast cancer in postmenopausal women
Mechanism of Action
Letrozole inhibits the enzyme aromatase, which is responsible for converting androgens into estrogens. By reducing estrogen levels, it decreases the growth of estrogen-dependent breast cancer cells.
Dosage and Administration
Adult: Initially, 2.5 mg once daily. May be taken with or without food.
Pediatric: Not recommended for pediatric patients.
Geriatric: No specific dosage adjustment necessary, but elderly patients should be monitored closely.
Renal Impairment: No specific dosage adjustment recommended.
Hepatic Impairment: Use with caution; no specific dosage adjustment.
Pharmacokinetics
Absorption: Well absorbed with peak plasma concentrations within 2 hours.
Distribution: Extensively distributed; approximately 60% bound to plasma proteins.
Metabolism: Primarily metabolized in the liver via hydroxylation and glucuronidation.
Excretion: Excreted mainly in urine; small amount in feces.
Half Life: Approximately 2 days (40-50 hours).
Contraindications
- Hypersensitivity to letrozole or any component of the formulation.
Precautions
- History of osteoporosis or risk factors for osteoporosis; may increase fracture risk.
- Monitor bone mineral density periodically.
- Use during pregnancy is contraindicated; it can cause fetal harm.
- Lactation: Not recommended during breastfeeding.
Adverse Reactions - Common
- Hot flashes (Common)
- Arthralgia (Common)
- Fatigue (Common)
- Nausea (Common)
Adverse Reactions - Serious
- Osteoporosis and fractures (Less common)
- Cardiovascular events (e.g., chest pain, arrhythmias) (Rare)
- Elevated liver enzymes (Rare)
Drug-Drug Interactions
- Tamoxifen (antagonizes letrozole activity)
Drug-Food Interactions
N/ADrug-Herb Interactions
N/ANursing Implications
Assessment: Assess breast cancer status, menopausal status, bone mineral density, cardiovascular status.
Diagnoses:
- Risk for osteoporosis related to decreased estrogen levels.
- Risk for injury due to fractures.
Implementation: Administer as prescribed, monitor for adverse effects, encourage bone health measures.
Evaluation: Monitor tumor response, bone density, and adverse reactions.
Patient/Family Teaching
- Take medication exactly as prescribed.
- Report any signs of osteoporosis (e.g., fractures), cardiovascular symptoms, or severe side effects.
- Maintain calcium and vitamin D intake, engage in weight-bearing exercises.
- Avoid pregnancy; use effective contraception.
Special Considerations
Black Box Warnings:
- Fetal harm; contraindicated in pregnancy.
Genetic Factors: No specific genetic markers required for use.
Lab Test Interference: May affect serum cholesterol levels.
Overdose Management
Signs/Symptoms: Unknown, but may include hormonal effects or nausea.
Treatment: Supportive care; no specific antidote. Consult poison control.
Storage and Handling
Storage: Store at room temperature, 20°C to 25°C (68°F to 77°F).
Stability: Stable when stored properly until the expiration date.