Contraindications/Precautions:

Your health care provider needs to know if you have any of these conditions: heart disease, circulation problems, a history of stroke or blood clot, severe liver disease, high cholesterol, osteoporosis, or low bone mineral density. Anastrozole may not work as well if you take it together with tamoxifen or an estrogen medication (such as hormone replacement therapy, estrogen creams, or birth control pills, injections, implants, skin patches, and vaginal rings). You may need to keep taking anastrozole for up to 5 years. In general, anastrozole should not be used in premenopausal females; anastrozole may not be able to inhibit the formation of estrogen from the ovaries and therefore is not expected to be effective, although it has been used successfully in the treatment of uterine leiomyomata in premenopausal women.(10) Hormone replacement therapy (i.e., exogenous estrogens) should not be administered concurrently with anastrozole. Hepatic cirrhosis due to alcohol abuse reduces apparent oral clearance of anastrozole by about 30%. Anastrozole should be used with caution in patients with mild to moderate hepatic impairment, and patients should be closely monitored for adverse effects. However, no dosage adjustments are recommended for patients with hepatic disease because plasma anastrozole concentrations remain within the range of those seen in normal patients. No studies have been conducted in patients with severe hepatic impairment. Consideration should be given to monitoring patients for signs and symptoms of osteoporosis, including decreased bone mineral density (BMD), during treatment with anastrozole, especially in patients with pre-existing osteoporosis, osteopenia, or risk factors for the development of osteoporosis. After a median follow-up of 68 months in the ATAC trial, the odds of bone fractures in patients taking anastrozole were significantly increased compared to patients taking tamoxifen (11% for anastrozole vs. 7.7% for tamoxifen, OR 1.49, 95% CI 1.25—1.77, P < 0.0001).(2) Similarly, in the combined analysis of the ABCSG trial 8 and the ARNO 95 trials, after a median follow-up of 36 months, the odds of bone fractures in patients taking anastrozole were significantly increased (2% for anastrozole vs. 1% for tamoxifen, OR 2.14, 95% CI 1.14—4.17, P = 0.015)(11). Anastrozole should be used with caution in women with pre-existing ischemic cardiac disease. In the ATAC trial, women with pre-existing ischemic heart disease had an increased incidence of ischemic cardiovascular events (17% of patients receiving anastrozole versus 4% of patients in the overall study population). Safety and efficacy of anastrozole in children have not been established. Anastrozole is classified as FDA pregnancy risk category X.(12) It is contraindicated for use in women who are pregnant or may become pregnant. Anastrozole may cause fetal harm when administered to pregnant women and offers no clinical benefit when administered to premenopausal women with breast cancer. Animal studies indicate that anastrozole increases pregnancy loss, both pre- and postimplantation. It crosses the placenta and causes fetal harm, including delayed fetal development, but there has been no evidence of teratogenicity. There have been no adequate studies in pregnant women, and anastrozole is only approved for the treatment of postmenopausal women, and should generally not be used in females of childbearing potential. If pregnancy occurs, however, while the patient is receiving anastrozole, she should be warned about the possible risk to the fetus and possible loss of pregnancy. It is not known whether anastrozole is excreted into breast milk. Because many drugs are excreted in human milk and because of the tumorigenicity shown for anastrozole in animal studies, or the potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue breast-feeding or to discontinue the drug, taking into account the importance of the drug to the mother. Anastrozole is contraindicated in pre-menopausal females, so use during lactation would not be expected.(12) This list may not include all possible contraindications.