Name: Anastrozole

Arimidex Dosage

Arimidex comes as 1 milligram (mg) tablets and is usually taken once a day for cancer.

If you're a woman taking Arimidex for infertility, your doctor may prescribe 1 mg to 5 mg for up to five days, beginning on the third day of your period.

Arimidex Overdose

If you suspect an overdose, you should contact a poison control center or emergency room immediately. You can get in touch with a poison control center at (800) 222-1222.

Missed Dose of Arimidex

If you miss a dose of Arimidex, try to take it as soon as you remember.

If it is almost time for the next dose, skip the missed dose and take your next dose at the regular time. Do not take two doses of the medication at the same time.

How supplied

Dosage Forms And Strengths

The tablets are white, biconvex, film-coated containing 1 mg of anastrozole. The tablets are impressed on one side with a logo consisting of a letter “A” (upper case) with an arrowhead attached to the foot of the extended right leg of the “A” and on the reverse with the tablet strength marking “Adx 1”.

Storage And Handling

These tablets are supplied in bottles of 30 tablets (NDC 0310-0201-30).


Store at controlled room temperature, 20-25°C (68-77°F) [see USP].

Distributed by: AstraZeneca Pharmaceuticals LP Wilmington, DE 19850. Revised: May 2014


Included as part of the PRECAUTIONS section.

Uses of Anastrozole

Anastrozole is a prescription medicine used:

  • in the treatment of early breast cancer:
    • after surgery 
    • in women whose breast cancer is hormone receptor-positive
  • ​​for the first treatment of breast cancer that has spread to nearby tissue or lymph nodes (locally advanced) or has spread to other parts of the body (metastatic), in women whose breast cancer is hormone receptor-positive or the hormone receptors are not known 
  • for treatment of advanced breast cancer, if the cancer has grown, or the disease has spread after tamoxifen therapy

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.

Anastrozole Brand Names

Anastrozole may be found in some form under the following brand names:

  • Arimidex

Anastrozole and Lactation

Tell your doctor if you are breastfeeding or are planning to breastfeed.

It is not known if anastrozole crosses into human milk. Because many medications can cross into human milk and because of the possibility for serious adverse reactions in nursing infants with use of this medication, a choice should be made whether to stop nursing or stop the use of this medication. Your doctor and you will decide if the benefits outweigh the risk of using anastrozole.

Other Requirements

  • Store anastrozole at 68°F to 77°F (20°C to 25°C).
  • Keep anastrozole and all medicines out of the reach of children.

Pregnancy & 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.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

Anastrozole dosing information

Usual Adult Dose for Breast Cancer:

Initial dose: 1 mg orally taken once a day
Duration of therapy: Until tumor progression (treatment of advanced breast cancer); unknown (adjuvant treatment of early breast cancer)

-Adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer;
-First-line treatment of postmenopausal women with hormone receptor-positive or hormone receptor unknown locally advanced or metastatic breast cancer;
-Second-line treatment of advanced breast cancer in postmenopausal women with disease progression following tamoxifen therapy.

Anastrozole Pharmacokinetics



Rapidly and well absorbed after oral administration, with peak plasma concentrations usually attained within 2 hours under fasting conditions.1

Steady-state plasma concentrations achieved in about 7 days.1


Serum estradiol concentrations reduced by approximately 70% within 24 hours of a 1-mg dose1 and by approximately 80% after 14 days of daily dosing.1


Suppression of serum estradiol concentrations maintained for up to 6 days after discontinuance of daily anastrozole administration.1


Food reduces rate but does not affect extent of absorption.1



Anastrozole crosses the placenta in animals;1 not known whether anastrozole crosses the placenta in humans.1

Not known whether anastrozole is distributed into milk.1

Plasma Protein Binding




Undergoes N-dealkylation, hydroxylation, and glucuronidation in the liver to multiple, pharmacologically inactive, metabolites.1

Elimination Route

Hepatic metabolism (85%) and renal excretion (10%).1


Approximately 50 hours.1

Special Populations

No evidence of altered pharmacokinetics observed in women >80 years of age compared with women <50 years of age.1

Individuals with severe renal impairment (Clcr <30 mL/minute): Renal clearance decreased by approximately 50%, but total body clearance decreased by only 10%.1

Individuals with stable hepatic cirrhosis (related to alcohol abuse): Clearance reduced by approximately 30% compared with those with normal hepatic function;1 however, plasma concentrations within range compared with individuals with normal hepatic function.1

Advice to Patients

  • Importance of providing patient with a copy of the manufacturer’s patient information.1

  • Risk of osteoporosis.1 Life-style changes (e.g., weight-bearing exercise, abstinence from smoking, moderation of alcohol consumption) and dietary supplementation with calcium and vitamin D advised.36 46 47 Importance of BMD monitoring.1 71 73

  • Risk of fetal harm if used during pregnancy.1 Contraindicated in premenopausal women.1

  • Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription (e.g., estrogens, raloxifene, tamoxifen), and OTC drugs, as well as any concomitant illnesses.1

  • Increased risk of ischemic cardiovascular events in patients with preexisting ischemic heart disease.1

  • Importance of immediately informing clinician if manifestations of a serious allergic reaction (e.g., swelling of face, lips, tongue, and/or throat; difficulty in swallowing and/or breathing) occur.1

  • Risk of hypercholesterolemia.1 Importance of lipoprotein monitoring.1 46

  • Importance of informing patients of other important precautionary information.1 (See Cautions.)

Drug Interactions


Co-administration of Anastrozole and tamoxifen in breast cancer patients reduced Anastrozole plasma concentration by 27%. However, the coadministration of Anastrozole and tamoxifen did not affect the pharmacokinetics of tamoxifen or N-desmethyltamoxifen. At a median follow-up of 33 months, the combination of Anastrozole tablets and tamoxifen did not demonstrate any efficacy benefit when compared with tamoxifen in all patients as well as in the hormone receptor-positive subpopulation. This treatment arm was discontinued from the trial [see CLINICAL STUDIES (14.1)]. Based on clinical and pharmacokinetic results from the ATAC trial, tamoxifen should not be administered with Anastrozole.


Estrogen-containing therapies should not be used with Anastrozole tablets as they may diminish its pharmacological action.


In a study conducted in 16 male volunteers, Anastrozole did not alter the exposure (as measured by Cmax and AUC) and anticoagulant activity (as measured by prothrombin time, activated partial thromboplastin time, and thrombin time) of both R- and S-warfarin.

Cytochrome P450

Based on in vitro and in vivo results, it is unlikely that co-administration of Anastrozole tablets 1 mg will affect other drugs as a result inhibition of cytochrome P450 [see CLINICAL PHARMACOLOGY (12.3)].

Pharmacologic Category

  • Antineoplastic Agent, Aromatase Inhibitor

Anastrozole Breastfeeding Warnings

AU and UK: Use is contraindicated during breastfeeding. US: A decision should be made whether to discontinue breastfeeding or to discontinue the drug, taking into account the importance of the drug to the mother Excreted into human milk: Unknown Excreted into animal milk: Data not available Comments: The effects in the nursing infant are unknown.