Version July 2025
Breast cancer, advanced: Postmenopausal patients: Oral: 1 mg once daily; continue until tumor progression or unacceptable toxicity.
Breast cancer, advanced, estrogen receptor positive, HER2 negative (off-label combination):
Postmenopausal patients: Oral: 1 mg once daily (in combination with abemaciclib) until disease progression or unacceptable toxicity (Ref). Aromatase inhibitors have also been used in combination with palbociclib and ribociclib (Ref).
Premenopausal or perimenopausal patients: Oral: 1 mg once daily (in combination with ribociclib [and the luteinizing hormone-releasing hormone (LHRH) agonist goserelin]) until disease progression or unacceptable toxicity (Ref).
Breast cancer, early, adjuvant therapy:
Postmenopausal patients: Oral: 1 mg once daily.
Premenopausal patients with high-risk disease (off-label use): Oral: 1 mg once daily (in combination with ovarian function suppression) (Ref).
Duration of therapy: The American Society of Clinical Oncology (ASCO) guidelines for adjuvant endocrine therapy of hormone-receptor positive breast cancer (focused update) recommend a duration of 5 to 10 years of adjuvant endocrine therapy; some patients may be appropriate candidates for extended aromatase inhibitor (AI) therapy for up to a total of 10 years based on disease recurrence risk and nodal disease status. Refer to the guidelines for specific recommendations based on menopausal status and tolerability (Ref). In a phase 3 study with another AI (letrozole), treatment with an additional 5 years of AI therapy (for a total of 10 years of AI therapy) demonstrated a significantly improved rate of disease-free survival and a decreased risk of disease recurrence and contralateral breast cancer (when compared to placebo), although overall survival was not significantly different between groups and bone-related adverse events occurred more frequently with letrozole versus placebo (Ref).
Breast cancer in male patients, hormone receptor positive (off-label use): Note: Should be used in combination with a gonadotropin-releasing hormone agonist/antagonist (Ref).
Adjuvant t herapy (alternative agent): May be used as adjuvant therapy in male patients with hormone receptor–positive breast cancer with a contraindication to tamoxifen. ASCO guidelines for management of male breast cancer recommend an initial duration of 5 years of adjuvant endocrine therapy; if there still is a high risk of recurrence, five additional years of endocrine therapy may be offered if the initial 5 years of adjuvant therapy have been completed and tolerated (Ref).
Advanced or metastatic disease: Oral: 1 mg once daily until disease progression or unacceptable toxicity (Ref). Endocrine therapy for males with advanced or metastatic, HR+, HER2-negative breast cancer may be sequenced as in females (Ref).
Breast cancer, risk reduction (off-label use): Postmenopausal patients ≥40 years of age: Oral: 1 mg once daily for 5 years (Ref).
Endometrial or uterine cancer, recurrent or metastatic (off-label use): Oral: 1 mg once daily (Ref).
Ovarian cancer, recurrent (off-label use): Oral: 1 mg once daily until disease progression or unacceptable toxicity (Ref).
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
The renal dosing recommendations are based upon the best available evidence and clinical expertise. Senior Editorial Team: Bruce Mueller, PharmD, FCCP, FASN, FNKF; Jason A. Roberts, PhD, BPharm (Hons), B App Sc, FSHP, FISAC; Michael Heung, MD, MS.
Altered kidney function: Oral: No dosage adjustment necessary for any degree of kidney dysfunction (Ref).
Hemodialysis, intermittent (thrice weekly): Dialyzable (~30%): Oral: No dosage adjustment necessary; when scheduled dose falls on dialysis days, administer after hemodialysis (Ref).
Peritoneal dialysis: Dialyzability unknown: Oral: No dosage adjustment necessary (Ref).
CRRT: Oral: No dosage adjustment necessary (Ref).
PIRRT (eg, sustained, low-efficiency diafiltration): Oral: No dosage adjustment necessary; when scheduled dose falls on PIRRT days, administer after PIRRT (Ref).
Mild to moderate impairment or stable hepatic cirrhosis: No dosage adjustment necessary.
Severe hepatic impairment: There are no dosage adjustments provided in the manufacturer's labeling. However, some sources do not recommend anastrozole use in severe impairment (Ref).
Refer to adult dosing.
Anastrozole is associated with decreased bone mineral density (BMD); decreases from baseline in total hip BMD (~7% loss after 5 years) and lumbar spine BMD (~6% loss after 5 years) have been reported (Ref). Anastrozole has been associated with bone resorption in postmenopausal females; therefore, osteoporosis and bone fracture may also occur (Ref).
Mechanism: Time-related; anastrozole decreases plasma estrogen levels up to 94% in postmenopausal females with estrogen-positive breast cancer. Low levels of estrogen have been associated with bone resorption leading to decreased BMD, especially at the lumbar spine (LS) and hip, resulting in increased osteoporosis and fracture risk (Ref).
Onset: Delayed; bone loss in LS occurred during the first 2 years of treatment with no additional loss observed in years 2 to 5. No slowing of bone loss occurred in the total hip BMD (Ref). There was a statistically significant LS BMD increase in the 2 years following discontinuation after 5 years of treatment (Ref).
Risk factors:
• Longer duration of therapy (Ref)
• Preexisting risk factors for decreased BMD, osteoporosis, and fracture (includes preexisting osteopenia, age >65 years, years since menopause, body mass index <20 kg/m2, personal/family history, chronic glucocorticoid use >6 months, prior fragility fracture history, low bone mineral density, rheumatoid arthritis, and smoking) (Ref).
Ischemic heart disease has been reported, with an increased incidence of ischemic cardiovascular events in patients with preexisting cardiovascular disease (CVD) (Ref). Angina pectoris and acute myocardial infarction (MI) have occurred. Ischemic stroke has also been reported with aromatase inhibitors (AIs) (Ref).
Mechanism: Non–dose-related; idiosyncratic. AIs, including anastrozole, reduce the protective effects of estrogen, leading to increases in atherosclerosis and vasoconstriction. Additionally, there is a dysregulation of lipid metabolism and the potential risk of dyslipidemia. These factors may increase the risk of cardiovascular events (Ref).
Risk factors:
• Longer durations therapy (Ref)
• Preexisting CVD or risk factors associated with CVD (Ref).
Musculoskeletal effects, including new onset or exacerbation of existing arthralgia, back pain, joint stiffness, myalgia, and/or ostealgia, may occur with anastrozole (Ref); pain may be severe and/or continuous (Ref). Aromatase inhibitor-induced arthralgia (AIA) presents with symmetrical joint pains most commonly affecting hands, wrists, and knees (Ref). Tendinopathy, tenosynovitis, tenosynovitis stenosans (trigger finger), rupture of tendon, and carpal tunnel syndrome may also occur (Ref). Musculoskeletal effects may significantly affect quality of life and adherence; treatment discontinuation due to musculoskeletal effects has been reported between 5% to 25% (Ref).
Mechanism: Not clearly established; multiple proposed mechanisms. Estrogen depletion may repress bone-protective effects, increase joint inflammation, and/or modulate endogenous opioid transmission. Another proposed mechanism involves induction of an autoimmune process and increased production of proinflammatory cytokines. A direct off-target effect may also occur (Ref).
Onset: Varied; occurs most commonly between 2 to 3 months after initiation (Ref).
Risk factors:
• Longer menopause duration (Ref)
• Menopausal symptom severity (Ref)
• Prior menopausal hormone therapy (Ref)
• Prior chemotherapy (especially taxanes) (Ref)
• Preexisting joint disease (Ref)
• Certain CYP19A1 single nucleotide polymorphisms (SNPs) have been associated with increased arthralgia symptoms and/or an association with discontinuation of therapy due to intolerable arthralgia (Ref)
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified.
>10%:
Cardiovascular: Angina pectoris (2% to 12%) (table 1), hypertension (5% to 13%), ischemic heart disease (4% to 17%) (table 2), vasodilation (25% to 36%)
|
Drug (Anastrozole) |
Comparator (Tamoxifen) |
Indication |
Number of Patients (Anastrozole) |
Number of Patients (Tamoxifen) |
Comments |
|---|---|---|---|---|---|
|
2% |
2% |
Breast cancer |
3,092 |
3,094 |
N/A |
|
12% |
5% |
Breast cancer |
216 |
249 |
In patients with preexisting ischemic heart disease |
|
Drug (Anastrozole) |
Comparator (Tamoxifen) |
Indication |
Number of Patients (Anastrozole) |
Number of Patients (Tamoxifen) |
Comments |
|---|---|---|---|---|---|
|
4% |
3% |
Breast cancer |
3,092 |
3,094 |
N/A |
|
17% |
10% |
Breast cancer |
216 |
249 |
In patients with preexisting ischemic heart disease |
Dermatologic: Skin rash (6% to 11%)
Endocrine & metabolic: Hot flash (12% to 36%)
Gastrointestinal: Gastrointestinal distress (29% to 34%), nausea (11% to 19%), vomiting (≤13%)
Nervous system: Asthenia (≤19%), depression (5% to 13%), fatigue (≤19%), headache (9% to 13%), mood disorder (19%), pain (11% to 17%)
Neuromuscular & skeletal: Arthralgia (15%; literature suggests incidence as high as 36%) (Howell 2005) (table 3), arthritis (17%) (table 4), back pain (10% to 12%) (table 5), ostealgia (7% to 11%) (table 6), osteoporosis (11%; literature suggests incidence as high as 20% in patients with preexisting osteopenia after 3- to 6-years of anastrazole) (Ref) (table 7)
|
Drug (Anastrozole) |
Comparator (Tamoxifen) |
Indication |
Number of Patients (Anastrozole) |
Number of Patients (Tamoxifen) |
|---|---|---|---|---|
|
15% |
11% |
Breast cancer |
3,092 |
3,094 |
|
Drug (Anastrozole) |
Comparator (Tamoxifen) |
Indication |
Number of Patients (Anastrozole) |
Number of Patients (Tamoxifen) |
|---|---|---|---|---|
|
17% |
14% |
Breast cancer |
3,092 |
3,094 |
|
Drug (Anastrozole) |
Comparator (Tamoxifen) |
Indication |
Number of Patients (Anastrozole) |
Number of Patients (Tamoxifen) |
|---|---|---|---|---|
|
12% |
13% |
Breast cancer |
506 |
511 |
|
10% |
10% |
Breast cancer |
3,092 |
3,094 |
|
Drug (Anastrozole) |
Comparator (Tamoxifen) |
Indication |
Number of Patients (Anastrozole) |
Number of Patients (Tamoxifen) |
|---|---|---|---|---|
|
11% |
10% |
Breast cancer |
506 |
511 |
|
7% |
6% |
Breast cancer |
3,092 |
3,094 |
|
Drug (Anastrozole) |
Comparator (Tamoxifen) |
Indication |
Number of Patients (Anastrozole) |
Number of Patients (Tamoxifen) |
|---|---|---|---|---|
|
11% |
7% |
Breast cancer |
3,092 |
3,094 |
Respiratory: Increased cough (8% to 11%), pharyngitis (6% to 14%)
1% to 10%:
Cardiovascular: Acute myocardial infarction (≤1%) (table 8), chest pain (5% to 7%), deep vein thrombosis (2%), edema (7%), peripheral edema (5% to 10%), thromboembolic disease (3% to 4%), thrombophlebitis (2% to 5%), venous thrombosis (3%)
|
Drug (Anastrozole) |
Comparator (Tamoxifen) |
Indication |
Number of Patients (Anastrozole) |
Number of Patients (Tamoxifen) |
Comments |
|---|---|---|---|---|---|
|
1% |
1% |
Breast cancer |
3,092 |
3,094 |
N/A |
|
0.9% |
3% |
Breast cancer |
216 |
249 |
In patients with preexisting ischemic heart disease |
Dermatologic: Alopecia (2% to 5%), diaphoresis (2% to 5%), pruritus (2% to 5%)
Endocrine & metabolic: Hypercholesterolemia (9%), weight gain (2% to 9%), weight loss (2% to 5%)
Gastrointestinal: Abdominal pain (7% to 9%), anorexia (5% to 7%), constipation (7% to 9%), diarrhea (8% to 9%), dyspepsia (7%), xerostomia (4% to 6%)
Genitourinary: Leukorrhea (2% to 3%), mastalgia (8%), pelvic pain (5%), urinary tract infection (8%), vaginal discharge (4%), vaginal dryness (2%), vaginal hemorrhage (1% to 5%), vaginitis (4%), vulvovaginitis (6%)
Hematologic & oncologic: Anemia (4%), leukopenia (2% to 5%), lymphedema (10%), neoplasm (5%), tumor flare (3%)
Hepatic: Increased gamma-glutamyl transferase (2% to 5%), increased serum alanine aminotransferase (2% to 5%), increased serum alkaline phosphatase (2% to 5%), increased serum aspartate aminotransferase (2% to 5%)
Infection: Infection (9%)
Nervous system: Anxiety (6%), carpal tunnel syndrome (3%) (table 9), cerebral ischemia (2%), confusion (2% to 5%), dizziness (6% to 8%), drowsiness (2% to 5%), hypertonia (3%), insomnia (6% to 10%), lethargy (1%), malaise (2% to 5%), nervousness (2% to 5%), paresthesia (5% to 7%)
|
Drug (Anastrozole) |
Comparator (Tamoxifen) |
Indication |
Number of Patients (Anastrozole) |
Number of Patients (Tamoxifen) |
|---|---|---|---|---|
|
3% |
0.7% |
Breast cancer |
3,092 |
3,094 |
Neuromuscular & skeletal: Arthropathy (6% to 7%) (table 10), bone fracture (10%) (table 11), myalgia (6%) (table 12), neck pain (2% to 5%), pathological fracture (2% to 5%)
|
Drug (Anastrozole) |
Comparator (Tamoxifen) |
Indication |
Number of Patients (Anastrozole) |
Number of Patients (Tamoxifen) |
Comments |
|---|---|---|---|---|---|
|
7% |
5% |
Breast cancer |
3,092 |
3,094 |
Described as “arthrosis” |
|
6% |
5% |
Breast cancer |
3,092 |
3,094 |
Described as “joint disorder” |
|
Drug (Anastrozole) |
Comparator (Tamoxifen) |
Indication |
Number of Patients (Anastrozole) |
Number of Patients (Tamoxifen) |
|---|---|---|---|---|
|
10% |
7% |
Breast cancer |
3,092 |
3,094 |
|
Drug (Anastrozole) |
Comparator (Tamoxifen) |
Indication |
Number of Patients (Anastrozole) |
Number of Patients (Tamoxifen) |
|---|---|---|---|---|
|
6% |
5% |
Breast cancer |
3,092 |
3,094 |
Ophthalmic: Cataract (6%)
Respiratory: Bronchitis (5%), dyspnea (8% to 10%), flu-like symptoms (6% to 7%), rhinitis (2% to 5%), sinusitis (6%)
Miscellaneous: Accidental injury (10%), cyst (5%), fever (2% to 5%)
<1%:
Dermatologic: Dermal ulcer, skin blister
Genitourinary: Endometrial carcinoma
Hepatic: Abnormal hepatic function tests, hepatitis, hepatomegaly, jaundice
Postmarketing:
Cardiovascular: Pulmonary embolism (Ref)
Dermatologic: Dermatitis (Ref), dermatologic disorder (lichen sclerosus) (Ref), erythema multiforme (Ref), pruritic rash (Ref), skin abnormalities related to radiation recall (Ref), Stevens-Johnson syndrome, urticaria (Ref), xeroderma (Ref)
Endocrine & metabolic: Hypercalcemia (Ref), hyperparathyroidism (Ref)
Hematologic & oncologic: Polycythemia (Ref)
Hepatic: Increased serum bilirubin, liver steatosis (Ref)
Hypersensitivity: Anaphylaxis, angioedema, hypersensitivity angiitis (Ref)
Nervous system: Cerebral infarction (Ref)
Neuromuscular & skeletal: Decreased bone mineral density (Ref), rupture of tendon, subacute cutaneous lupus erythematosus (Ref), tardive dyskinesia (Ref), tendinopathy (Ref), tenosynovitis (including tenosynovitis stenosans [trigger finger])
Ophthalmic: Cystoid macular edema (Ref), optic neuritis (Ref), papilledema (Ref), retinal thrombosis (Ref), uveitis (Ref), vitreous traction (Ref)
Respiratory: Pulmonary cryptococcosis (Ref)
Hypersensitivity to anastrozole or any component of the formulation.
Canadian labeling: Additional contraindications (not in the US labeling): Pregnancy, breastfeeding.
Disease-related concerns:
• Hepatic impairment: Plasma concentrations in patients with stable hepatic cirrhosis were within the range of concentrations seen in normal subjects across all clinical trials.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Tablet, Oral:
Arimidex: 1 mg
Generic: 1 mg
Yes
Tablets (Anastrozole Oral)
1 mg (per each): $6.94 - $13.50
Tablets (Arimidex Oral)
1 mg (per each): $65.29
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Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Tablet, Oral:
Arimidex: 1 mg
Generic: 1 mg
Oral: May be administered with or without food.
Hazardous agent (NIOSH 2024 [table 2]).
Use appropriate precautions for receiving, handling, storage, preparation, dispensing, transporting, administration, and disposal. Follow NIOSH and USP 800 recommendations and institution-specific policies/procedures for appropriate containment strategy (NIOSH 2023; NIOSH 2024; USP-NF 2020).
Note: Facilities may perform risk assessment of some hazardous drugs to determine if appropriate for alternative handling and containment strategies (USP-NF 2020). Refer to institution-specific handling policies/procedures.
Breast cancer:
First-line treatment of locally advanced or metastatic breast cancer (hormone receptor–positive or unknown) in postmenopausal patients.
Adjuvant treatment of early hormone receptor-positive breast cancer in postmenopausal patients.
Treatment of advanced breast cancer in postmenopausal patients with disease progression following tamoxifen therapy.
Breast cancer, high-risk, hormone receptor–positive, adjuvant endocrine therapy in premenopausal patients (in combination with ovarian function suppression); Breast cancer in male patients, hormone receptor–positive; Endometrial or uterine cancers (recurrent or metastatic); Ovarian cancer (recurrent); Risk reduction for breast cancer in postmenopausal patients
Anastrozole may be confused with anagrelide, letrozole
Arimidex may be confused with Aromasin
The Institute for Safe Medication Practices (ISMP) includes this medication among its list of drug classes (chemotherapeutic agent, parenteral and oral) which have a heightened risk of causing significant patient harm when used in error (High-Alert Medications in Acute Care, Community/Ambulatory Care, and Long-Term Care Settings).
None known.
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the drug interactions program by clicking on the “Launch drug interactions program” link above.
Estrogen Derivatives: May decrease therapeutic effects of Anastrozole. Risk X: Avoid
Levomethadone: Aromatase Inhibitors may increase serum concentration of Levomethadone. Risk C: Monitor
Methadone: Aromatase Inhibitors may increase serum concentration of Methadone. Risk C: Monitor
Tamoxifen: May decrease serum concentration of Anastrozole. Risk X: Avoid
Evaluate pregnancy status prior to therapy. Verify the patient is not pregnant prior to treatment initiation in patients who could become pregnant. Patients who could become pregnant should use effective contraception during therapy and for at least 3 weeks after the last anastrozole dose.
Based on the mechanism of action and data from animal reproduction studies, anastrozole may cause fetal harm if exposure occurs during pregnancy.
It is not known if anastrozole is present in breast milk.
Due to the potential for serious adverse reactions in the breastfed infant, the manufacturer does not recommend breastfeeding during therapy or for 2 weeks after the last anastrozole dose.
Hormone-receptor status. Bone mineral density at baseline and periodically thereafter; total cholesterol and LDL. Pregnancy test (prior to treatment in patients who could become pregnant). Monitor adherence.
Breast cancer risk reduction (off-label use): Bone mineral density at baseline, mammograms, and clinical breast exam at baseline and at least every 2 years (Cuzick 2014).
Cardiovascular monitoring for patients with breast cancer: Comprehensive assessment prior to treatment including a history and physical examination, screening for cardiovascular disease risk factors such as hypertension, diabetes, dyslipidemia, obesity, and smoking; estimate 10-year cardiovascular disease risk in patients without cardiovascular disease at baseline; assess cardiovascular risk annually in patients with a high 10-year risk (ASCO [Armenian 2017]; ESC [Lyon 2022]).
Anastrozole is a potent and selective nonsteroidal aromatase inhibitor. By inhibiting aromatase, the conversion of androstenedione to estrone, and testosterone to estradiol, is prevented, thereby decreasing tumor mass or delaying progression in patients with tumors responsive to hormones. Anastrozole causes an 85% decrease in estrone sulfate levels.
Onset of estradiol reduction: 70% reduction after 24 hours; 80% after 2 weeks of therapy
Duration of estradiol reduction: 6 days
Absorption: Well absorbed; extent of absorption not affected by food
Protein binding, plasma: 40%
Metabolism: Extensively hepatic (~85%) via N-dealkylation, hydroxylation, and glucuronidation; primary metabolite (triazole) inactive
Half-life elimination: ~50 hours
Time to peak, plasma: ~2 hours without food; 5 hours with food
Excretion: Feces; urine (urinary excretion accounts for ~10% of total elimination, mostly as metabolites)
Altered kidney function: Renal clearance is decreased proportionally with CrCl and was approximately 50% lower in those with severe renal function impairment (CrCl less than 30 mL/minute per 1.73 m2); this reduced total body clearance by 10%.
Hepatic function impairment: Oral clearance was approximately 30% lower in those with stable hepatic cirrhosis, but plasma concentrations were within normal range.
