Letrozole
FEMARA
What it isAromatase inhibitor; hormone receptor-positive breast cancer, and off label for ovulation induction.
Why this oneSuperior disease-free survival to tamoxifen after menopause, and in PCOS it induces ovulation more effectively than clomiphene.
What limits itAccelerated bone loss and arthralgia. Ineffective before menopause unless ovarian function is suppressed.
FDA-approved for
- breast cancer (1997)
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Breast cancer — adjuvant, extended adjuvant, or advanced (ER+ postmenopausal) | Adults | 2.5 mg QD | 2.5 mg QD | 2.5 mg QD |
Renal No adjustment if CLcr ≥10 mL/min.
Hepatic No adjustment for mild–moderate; cirrhosis with severe hepatic impairment: reduce 50% to 2.5 mg every other day.
Instructions
- Take orally with or without food.
- Continue until tumor relapse/progression.
Contraindications
- Pregnancy (fetal harm)
Cautions
- Decreased bone mineral density — consider BMD monitoring
- Increases in total cholesterol — consider monitoring
- Fatigue, dizziness, somnolence — caution driving/operating machinery
- Embryo-fetal toxicity; use effective contraception
Adverse reactions
- Hot flashes, arthralgia
- Flushing, asthenia, edema, headache, dizziness
- Hypercholesterolemia, increased sweating, bone pain, musculoskeletal pain
Pregnancy Contraindicated — can cause fetal harm (spontaneous abortion, congenital defects).
Lactation Unknown if in human milk; advise not to breastfeed during and for ≥3 weeks after last dose.
NO BOXED WARNINGS
Principal riskAccelerated bone loss and arthralgia
Cost, est. cash$10–$1,000/month
Generic entry2008
Classes and tags
Clinical profile
Legacy pregnancy categoryMultiple / indication-, trimester- or formulation-dependent
Defining liabilityThrombotic, metabolic, hepatic, skeletal or reproductive toxicity varies by hormonal target.
Mechanism of action: Letrozole ballicule
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