Dosing and uses of Arimidex (anastrozole)
Adult dosage forms and strengths
tablet
- 1mg
Breast Cancer
Postmenopausal women
Advanced
- 1 mg PO once daily; continue until tumor progression
Early
- Adjuvant treatment: 1 mg PO qDay; optimal duration unknown; 5 years in clinical trials
Administration
May be taken with or without food
Hepatic Impairment
Mild-to-moderate impairment or stable hepatic cirrhosis: Dose adjustment not necessary
Severe hepatic impairment: Not studied
Pediatric dosage forms and strengths
Use not recommended
Arimidex (anastrozole) adverse (side) effects
>10%
Hot flashes (12-36%)
Vasodilation (25-36%)
Fatigue (19%)
Mood disturbances (19%)
Nausea and vomiting (19%)
Weakness (16-19%)
Arthritis (17%)
Pain (17%)
Arthralgia (2-15%)
Pharyngitis (14%)
Depression (13%)
Hypertension (2-13%)
Bone pain (11%)
Increased cough (11%)
Osteoporosis (11%)
Rash (8-11%)
1-10%
Accidental injury (10%)
Back pain (10%)
Fracture (10%)
Headache (10%)
Insomnia (10%)
Peripheral edema (10%)
Dyspnea (8-10%)
Abdominal pain (9%)
Infection (9%)
Lymphedema (9%)
Diarrhea (8-9%)
Constipation (7-9%)
Breast pain (8%)
Dizziness (8%)
Urinary tract infection (8%)
Chest pain (7%)
Dyspepsia (7%)
Paresthesia (5-7%)
Anxiety (6%)
Cataracts (6%)
Flu syndrome (6%)
Sinusitis (6%)
Vulvovaginitis (6%)
Xerostomia (6%)
Breast neoplasm (5%)
Bronchitis (5%)
Cyst (5%)
Diaphoresis (5%)
Neoplasm (5%)
Vaginal bleeding (5%)
Fractures of spine, hip, or wrist (4%)
Ischemic cardiovascular disease (4%)
Vaginal hemorrhage (4%)
Vaginitis (4%)
Leukorrhea (3-4%)
Deep vein thrombosis (2%)
Endometrial cancer (intact uterus at baseline) (2%)
Ischemic cerebrovascular event (2%)
Weight gain (2%)
Lethargy (1%)
Postmarketing Reports
Hepatitis; increased alkaline phosphatase, aminotransferases, gamma-glutamyl transferase, and bilirubin
Allergic reactions, including angioedema, urticaria, and anaphylaxis
Rash, including mucocutaneous disorders (eg, erythema multiforme, Stevens-Johnson syndrome)
Myalgia, trigger finger, and hypercalcemia (with or without increase in parathyroid hormone)
Warnings
Contraindications
Hypersensitivity
May cause fetal harm or loss; use is contraindicated in women who are or may become pregnant
Cautions
Increased incidence of ischemic cardiovascular events in women with preexisting ischemic heart disease; use only if benefits greatly outweigh risks
Decreases lumbar spine and total hip bone mineral density; increased risk of fractures and osteoporosis
Elevated serum cholesterol reported; monitor closely
Affords no clinical benefit to premenopausal women with breast cancer
Increased risk of ischemic cardiovascular events in patients with pre-existing ischemic cardiac disease
Pregnancy and lactation
Pregnancy category: X
Lactation: Unknown whether drug is excreted in milk; not recommended given potential for serious adverse reactions in nursing infants
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.
Pharmacology of Arimidex (anastrozole)
Mechanism of action
Selective nonsteroidal aromatase inhibitor; prevents conversion of androstenedione to estrone and estradiol in peripheral tissues, thereby significantly lowering serum estradiol concentrations; has no effect on adrenal corticosteroids or aldosterone
Absorption
Peak plasma concentration: 2 hr without food; 5 hr with food
Onset: 24 hr (70% reduction); 2 weeks (80% reduction)
Time to steady-state levels: 7 days
Distribution
Protein bound: 40%
Metabolism
Metabolized in liver via N-dealkylation, hydroxylation, and glucuronidation (85%)
Metabolite: Triazole (inactive)
Enzymes inhibited: CYP1A2, CYP2C9, CYP3A4 (at high concentrations; inhibition not significant at usual dose)
Elimination
Half-life: 50 hr
Dialyzable: Yes
Excretion: Urine (10%)
