DrugindexOnline^{2nd edition}

Pronouncation: (an-ASS-troe-zole)
Class: Aromatase inhibitor

Trade Names:
Arimidex
- Tablets for oral use 1 mg

Mechanism of Action

Pharmacology

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

Pharmacokinetics

Distribution

40% protein bound.

Metabolism

Metabolized in the liver (N-dealkylation, hydroxylation, and glucuronidation).

Elimination

T _½ is approximately 50 h; approximately 10% is excreted in the urine as unchanged drug within 72 h and approximately 60% is excreted in the urine as metabolites.

Special Populations

Renal Function Impairment

Renal Cl decreased proportionally with Ccr and was approximately 50% lower in those with severe renal function impairment (Ccr less than 30 mL/min/1.73 m ² ); however, this did not influence total body Cl.

Hepatic Function Impairment

Oral Cl was approximately 30% lower in those with stable hepatic cirrhosis but plasma concentrations were within normal range.

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.

Contraindications

None well documented.

Dosage and Administration

Breast Cancer
Adults

PO 1 mg every day.

Storage/Stability

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

Drug Interactions

No significant drug interactions have been noted. May reduce blood estradiol levels. This may affect the efficacy of oral contraceptives.

Laboratory Test Interactions

Elevations of GGT levels have been observed among patients with liver metastases.

Adverse Reactions

Cardiovascular

Hypertension; thrombophlebitis; edema; vasodilation; chest pain.

CNS

Asthenia; headache; paresthesias; somnolence; confusion; insomnia; anxiety; dizziness; depression; hypertonia; lethargy; paresthesia.

Dermatologic

Alopecia; pruritus; rash; sweating.

GI

Low to moderate potential for nausea and vomiting; diarrhea; constipation; anorexia; increased LFTs (GGT, AST, ALT); GI disturbances; abdominal pain; dry mouth.

Genitourinary

UTIs; vaginal dryness; menstrual bleeding; sexual inactivity; atrophy of the female reproductive organs; pregnancy loss; pelvic pain.

Respiratory

Dyspnea; sinusitis; bronchitis; cough increased; pharyngitis.

Miscellaneous

Myalgia; arthralgia; breast pain; hot flashes; pain; back pain; peripheral edema; bone pain; flu-syndrome; tumor flare; weight gain; leukorrhea; edema.

Precautions

Monitor Adverse reactions Notify health care provider of pain, swelling, redness or warmth in calves; sudden severe headache; visual disturbances; or weakness or numbness of arms or legs.

Pregnancy

Category D .

Lactation

Exercise caution when administering to a breast-feeding woman.

Children

Safety and efficacy not established.

Estrogen receptor negative

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

Patient Information

• Advise patient to take 1 tablet every day.
• Advise patient that medication can be taken without regard to meals, but to take with food if GI upset occurs.
• Advise patient that if a dose is missed, take it as soon as possible, but if close to the next dose, do not double the dose to catch up, and take the next dose as scheduled.
• Instruct patient to immediately report any of the following to the health care provider: pain in groin or calves; sharp chest pain or sudden shortness of breath; sudden severe headache; dizziness or fainting; 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.