Anastrozole

Trade Names:
Arimidex
- Tablets 1 mg

Pharmacology

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A selective nonsteroidal aromatase inhibitor. It lowers serum estradiol concentrations.

Pharmacokinetics

Absorption

Absorption is rapid, with T _max at about 2 h. Food decreases C _max by 16% and delays T _max to 5 h.

Distribution

40% protein bound.

Metabolism

Metabolized in the liver (N-dealkylation, hydroxylation, and glucuronidation) via CYP1A2, CYP2C8/2C9, and CYP3A4.

Elimination

Half-life is approximately 50 h; approximately 10% is excreted in the urine. Approximately 85% undergoes hepatic metabolism.

Special Populations

Renal Cl decreased proportionally with CrCl and was approximately 50% lower in those with severe renal function impairment (CrCl less than 30 mL/min per 1.73 m ² ); this reduced total body Cl by 10%. No dosage adjustment is needed for renal impairment.

Oral Cl was approximately 30% lower in those with stable hepatic cirrhosis, but plasma concentrations were within normal range. Dosage adjustment is not necessary. Has not been studied in patients with severe hepatic impairment.

The pharmacokinetics of anastrozole are not affected by age.

Safety and efficacy not established.

Indications and Usage

Advanced breast cancer in postmenopausal women with progression following tamoxifen therapy; first-line treatment of postmenopausal women with hormone receptor–positive or hormone receptor unknown locally advanced or metastatic breast cancer; for adjuvant treatment of postmenopausal women with hormone receptor–positive early breast cancer.

Unlabeled Uses

Male infertility.

Contraindications

Women who are or plan to become pregnant; premenopausal women; patients who have shown hypersensitivity reaction to the drug or any of the excipients.

Dosage and Administration

PO 1 mg every day with or without food.

PO 1 mg once daily for a mean duration of 4.7 mo (range, 1 to 24 mo).

Storage/Stability

Store tablets at controlled room temperature (68° to 77°F).

Drug Interactions

Estrogens may diminish the actions of anastrozole. Coadministration is not recommended.

May reduce blood estradiol levels. This may affect the efficacy of oral contraceptives.

Coadministration is not recommended.

Laboratory Test Interactions

Elevations of gamma glutamyltransferase (GGT) levels have been observed among patients with liver metastases.

Adverse Reactions

Cardiovascular

Vasodilation (36%); hypertension (13%); ischemic CV disease, thromboembolic disease (4%); venous thromboembolic events (3%); deep venous thromboembolic events, ischemic cerebrovascular event (2%).

CNS

Asthenia, mood disturbances (19%); headache (18%); depression (13%); insomnia (10%); dizziness (8%); paraesthesia (7%); anxiety (6%); hypertonia (3%); lethargy (1%).

Dermatologic

Rash (11%); sweating (5%); erythema multiforme, mucocutaneous disorder, Stevens-Johnson (postmarketing).

EENT

Pharyngitis (14%); cataract specified (6%).

GI

GI disturbance (34%); nausea (20%); vomiting (11%); abdominal pain, constipation, diarrhea (9%); anorexia (8%); dyspepsia, GI disorder (7%); dry mouth (6%).

Genitourinary

Breast pain, UTI (8%); vulvovaginitis (6%); breast neoplasm, vaginal hemorrhage (5%); vaginal discharge, vaginitis (4%); leucorrhea (3%); vaginal dryness (2%).

Hematologic-Lymphatic

Lymphedema (10%); anemia (4%); leukopenia (postmarketing).

Hepatic

Increased alkaline phosphatase, ALT, AST, bilirubin, GGT; hepatitis (postmarketing).

Hypersensitivity

Allergic reactions including anaphylaxis, angioedema, and urticaria (postmarketing).

Metabolic-Nutritional

Edema (11%); peripheral edema (10%); hypercholesterolemia, weight gain (9%).

Musculoskeletal

Musculoskeletal events (36%); arthritis (17%); arthralgia (15%); back pain, bone pain (12%); osteoporosis (11%); fracture (10%); arthrosis, pelvic pain (7%); joint disorder, myalgia (6%).

Respiratory

Dyspnea, increased cough (11%); sinusitis (6%); bronchitis (5%).

Miscellaneous

Hot flashes (36%); pain (17%); accidental injury (10%); infection (9%); chest pain, flu syndrome (7%); cyst, neoplasm (5%); tumor flare (3%).

Precautions

Pregnancy

Category X .

Lactation

Unknown

Children

Safety and efficacy not established.

Bone effects

May decrease BMD.

Cardiac effects

Consider the risks and benefits in patients with preexisting ischemic heart disease.

Cholesterol

May increase serum cholesterol levels.

Estrogen receptor–negative

Patients who did not respond to tamoxifen rarely respond to anastrozole.

Patient Information

• Advise patient that medication can be taken without regard to meals, but to take with food if GI upset occurs.
• Advise women that anastrazole may cause fetal harm. Advise patients to avoid becoming pregnant.
• Instruct patient to immediately report any of the following to the health care provider: dizziness or fainting, pain in groin or calves, sharp chest pain or sudden shortness of breath, sudden severe headache, vision or speech problems, weakness or numbness of arms or legs.
• Advise patient that drug may cause dizziness and to use caution while driving or performing other tasks requiring mental alertness.
• Advise patient that this medicine may decrease bone strength, which may increase the risk of fractures.
• Advise patient with preexisting ischemic heart disease of the increased risk of CV events.
• Advise patients that this medication may increase cholesterol.

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