- Nonsteroidal aromatase inhibitor (AI).
- Inhibits aromatase enzyme (CYP19), blocking conversion of androgens to estrogens in peripheral tissues.
- Leads to profound reduction in circulating estrogen — effective in postmenopausal women (ovaries no longer primary estrogen source).
Oncology Indications:
- Hormone receptor–positive (ER+ and/or PR+) breast cancer in postmenopausal women:
- Adjuvant therapy (5 years, or sequential after tamoxifen).
- Extended adjuvant therapy beyond 5 years of tamoxifen.
- First-line treatment for metastatic disease.
- Breast cancer prevention in postmenopausal women at high risk (off-label in some regions).
Dose & Administration:
- 1 mg orally once daily.
- Can be taken with or without food.
Pharmacist Considerations: Adverse Effects:
- Common: hot flashes, arthralgia/myalgia, fatigue, mild nausea.
- Bone health: increased risk of osteoporosis and fractures due to estrogen depletion.
- Metabolic effects: mild dyslipidemia possible.
Monitoring:
- Bone density at baseline and periodically (DEXA scans).
- Lipid profile if patient has cardiovascular risk.
- Assessment for joint pain/stiffness (arthralgia management is common reason for discontinuation).
Counseling Points:
- Emphasize adherence — missing doses can compromise estrogen suppression.
- Maintain bone health: adequate calcium/vitamin D, weight-bearing exercise.
- Report new or worsening bone pain (could signal osteoporosis or metastases).
- AI therapy only effective in postmenopausal women — premenopausal patients require ovarian suppression (e.g., goserelin) if using AI.
Drug Interactions:
- No major CYP-mediated interactions of clinical significance, but always review concomitant medications.