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Arimidex (Anastrozole) - Drug Interactions, Contraindications, Overdosage, etc




Co-administration of anastrozole and tamoxifen in breast cancer patients reduced anastrozole plasma concentration by 27%. However, the co-administration 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 ARIMIDEX 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 ]. 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 ARIMIDEX 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 ARIMIDEX 1 mg will affect other drugs as a result of inhibition of cytochrome P450 [see Clinical Pharmacology ].


Clinical trials have been conducted with ARIMIDEX, up to 60 mg in a single dose given to healthy male volunteers and up to 10 mg daily given to postmenopausal women with advanced breast cancer; these dosages were tolerated. A single dose of ARIMIDEX that results in life-threatening symptoms has not been established. There is no specific antidote to overdosage and treatment must be symptomatic. In the management of an overdose, consider that multiple agents may have been taken. Vomiting may be induced if the patient is alert. Dialysis may be helpful because ARIMIDEX is not highly protein bound. General supportive care, including frequent monitoring of vital signs and close observation of the patient, is indicated.


Pregnancy and Premenopausal Women

ARIMIDEX may cause fetal harm when administered to a pregnant woman and offers no clinical benefit to premenopausal women with breast cancer. ARIMIDEX is contraindicated in women who are or may become pregnant. There are no adequate and well-controlled studies in pregnant women using ARIMIDEX. If ARIMIDEX is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to a fetus or potential risk for loss of the pregnancy [see Use in Specific Populations ].


ARIMIDEX is contraindicated in any patient who has shown a hypersensitivity reaction to the drug or to any of the excipients. Observed reactions include anaphylaxis, angioedema, and urticaria [see Adverse Reactions ].

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