How Arimidex Works

ARIMIDEX mechanism of action – androgens

In a complex series of reactions beginning with cholesterol, the adrenal gland synthesizes steroid hormones, including aldosterone, cortisol, androgens, and estrogens.⁶

Aromatase, a cytochrome P450-dependent enzyme, acts at the last step in the synthesis of estrogen only, catalyzing the conversion of androgens to estrogens.⁷

The conversion of androgens to estrogens occurs at peripheral sites such as in muscle, fat, and liver, and also in breast tumors.⁸ The importance of tumor-generated estrogens is uncertain.

ARIMIDEX mechanism of action – aromatase

ARIMIDEX, a potent and selective nonsteroidal aromatase inhibitor, binds to the aromatase enzyme in place of androgens, inhibiting aromatase activity.^9,10

ARIMIDEX significantly lowers serum estradiol concentrations.

ARIMIDEX has no detectable effect on formation of adrenal corticosteroids or aldosterone.

Important Information About ARIMIDEX Tablets

ARIMIDEX is indicated for adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer.

ARIMIDEX is indicated for first-line treatment of postmenopausal women with hormone receptor-positive or hormone receptor-unknown locally advanced or metastatic breast cancer.

ARIMIDEX is indicated for the treatment of advanced breast cancer in postmenopausal women with disease progression following tamoxifen therapy. Patients with estrogen receptor-negative disease and patients who did not respond to previous tamoxifen therapy rarely responded to ARIMIDEX.

Important Safety Information About ARIMIDEX

ARIMIDEX is only for postmenopausal women. ARIMIDEX can cause fetal harm when administered to a pregnant woman. Before starting treatment with ARIMIDEX, pregnancy must be excluded (see WARNINGS section of full Prescribing Information).

Common side effects seen with ARIMIDEX vs tamoxifen in the early breast cancer trial after 5 years of treatment include hot flashes (36% vs 41%), joint disorders (including arthritis, arthrosis, arthralgia) (36% vs 29%), asthenia (19% vs 18%), mood disturbances (19% vs 18%), pain (17% vs 16%), pharyngitis (14% vs 14%), nausea and vomiting (13% vs 12%), depression (13% vs 12%), hypertension (13% vs 11%), osteoporosis (11% vs 7%), peripheral edema (10% vs 11%), and headache (10% vs 8%). Fractures, including fractures of the spine, hip, and wrist, occurred more frequently with ARIMIDEX vs tamoxifen (10% vs 7%).

Compared to baseline, ARIMIDEX showed a mean decrease in both lumbar spine and total hip bone mineral density. Tamoxifen showed a mean increase in these measurements. Nine percent of patients receiving ARIMIDEX had an elevated serum cholesterol vs 3.5% of patients receiving tamoxifen.

The common side effects seen with ARIMIDEX in advanced breast cancer trials include hot flashes (26.5%), nausea (18.6%), asthenia (16.4%), pain (13.8%), back pain (11.9%), bone pain (10.7%), and increased cough (10.9%). Joint pain/stiffness has been reported in association with the use of ARIMIDEX.

Clinical and pharmacokinetic results suggest that tamoxifen should not be administered with ARIMIDEX. Estrogen-containing therapies should not be used with ARIMIDEX, as they may diminish its pharmacologic action.

Please click here for full Prescribing Information.

ARIMIDEX is a registered trademark of the AstraZeneca group of companies.