Trade name Arimidex

Bioavailability 83-85%

Protein binding 40%

Metabolism is 85% hepatic.

Biological half-life 46.8 h.

Excretion 11% renal.

Arimidex (anastrozole) 1 mg tablets

A non-steroidal aromatase-inhibiting drug approved for treatment of breast cancer after surgery, as well as for metastasis in both pre and post-menopausal women.

The severity of breast cancer can be increased by estrogen, as sex hormones cause hyperplasia, and differentiation at estrogen receptor sites.

Works by inhibiting the synthesis of estrogen.

The ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial was an international randomised controlled trial of 9366 women with localized breast cancer who received either anastrozole, tamoxifen, or both for five years, followed by five years of follow-up.

After more than 5 years the group that received anastrozole had significantly better clinical results than the tamoxifen group.

Anastrozole is the pref2242ed medical therapy for postmenopausal women with localized breast cancer, which is estrogen receptor (ER) positive.

Another study found that the risk of recurrence was reduced by 40%, but was associated with an increased risk of bone fractures.

ER positive patients benefited from switching from tamoxifen to anastrozole in patients who have completed 2 years’ adjuvant tamoxifen.

Significantly reduces the incidence of breast cancer in postmenopausal women relative to placebo, and while there were side effects related to estrogen deprivation.

ABCSG-16 phase 3 trial found that postmenopausal women with hormone receptor-positive breast cancer who underwent 5 additional years of anastrozole therapy received no extra benefit compared with women who had 2 years of additional therapy.

Women who switched to anastrozole after two years on tamoxifen reported twice as many fractures as those who continued to take tamoxifen (2.1% compared to 1%).

Anastrozole binds reversibly to the aromatase enzyme through competitive inhibition, inhibits the conversion of androgens to estrogens in peripheral tissues.

Excess estradiol in men can cause benign prostatic hyperplasia, gynecomastia, and symptoms of hypogonadism.

Dosages of 0.5 mg to 1 mg a day reduce serum estradiol by approximately 50% in men, which differs in postmenopausal women.

May be used off-label in children with precocious puberty, or children with pubertal gynecomastia.

The benefits of the aromatase inhibitor anastrozole for breast cancer prevention in high-risk postmenopausal women extend well beyond the five-year treatment period, according to long-term data from the International Breast Cancer Intervention Study II (IBIS-II) Prevention trial: producing continuing benefits right out to 12 years,

After a median follow-up of five years, showed a 61% reduction in new breast cancers (from 4.6% with placebo to 1.8% with anastrozole).

Long-term data show there continues to be a 36% reduction in new cancers in years five to 12 .

It is the pref2242ed therapy for breast cancer prevention in high-risk postmenopausal women.

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