Arimidex [Anastrozole]marketed by AstraZeneca Pharmaceuticals LP is a drug indicated in the treatmentof adjuvant treatment [treatment following surgery with or without radiation]of postmenopausal women with hormone receptor-positive early breast cancer.

It decreases the amount of estrogen in the body.

                                                

It is chemically described as 1, 3-Benzenediacetonitrile, a,a, a', a'-

Tetramethyl-5-(1H-1, 2, 4-triazol-1-ylmethyl).

 

Estrogen receptorpositive breast cancer:

 

The estrogen receptor (ER) is a member of the nuclearhormone family of intracellular receptors which is activated by the hormone17β-estradiol (estrogen).

The main function of the estrogen receptor is to act as aDNA binding transcription factor which would regulate gene expression. Apartfrom this function, the estrogen receptor also has additional functionsindependent of DNA binding.

There are two types of estrogen receptors, α and β, bothencoded by different genome [ESR1 on the sixth chromosome and ESR2 on thefourteenth chromosome respectively]

In 70% cases of breast cancer, over expression of theestrogen receptor has been found, termed as ER positive.

Researches postulate two theses for the occurrence of thesame:

-       Binding ofestrogen to the ER stimulates proliferation of mammary cells, this result inincrease in cell division and DNA replication leading to mutations.

-       It is thoughtthat estrogen metabolism could lead to production of genotoxic wastes.

 

Both these processes could result in the disruption of cellcycle, apoptosis and DNA repair and therefore tumor formation. ERα is certainlyassociated with more differentiated tumors, while evidence that ERβ is involvedis controversial. Different versions of the ESR1 gene have been identified(with single-nucleotide polymorphisms) and are associated with different risksof developing breast cancer.

 

Particularly in postmenopausal women, the principal sourceof circulating estrogen (primarily Estradiol) is conversion ofadrenally-generated androstenedione to estrone by aromatase in peripheraltissues, with further conversion of estrone to estradiol. Many breast cancersalso contain aromatase; the importance of tumor-generated estrogens isuncertain.

 

Arimidex [Anastrozole] is approved for the initial treatmentof postmenopausal women with hormone receptor-positive or hormonereceptor-unknown locally advanced or metastatic breast cancer and for thetreatment of postmenopausal women with advanced breast cancer that hasprogressed following treatment with tamoxifen. Patients with hormonereceptor-negative disease and patients who did not previously respond totamoxifen therapy rarely responded to Arimidex [Anastrozole]

 

Anastrozole belongs to the class of aromatase inhibitors,where it inhibits the enzyme aromatase which is responsible for the conversionof androgens to estrogen, meaning it selectively lowers the serum estradiollevels and at the same time doesn't have any effect on the formation of adrenalcorticosteroids or aldosterone.

Basically it is a selective non steroidal aromataseinhibitor.

 

Orally administered Arimidex [anastrozole] is well absorbedinto the systemic circulation. Its absorption is not affected by food.

With a half life of around 50 hours in post-menopausalfemales, it is excreted mainly via hepatic metabolism and by a lesser extent byrenal metabolism

 

Indications andUsage:

 

Indications:

Adjuvant treatment of postmenopausal women with hormonereceptor positive early breast cancer.

 

Arimidex [Anastrozole] is indicated for the first-linetreatment of postmenopausal women with hormone receptor positive or hormonereceptor unknown locally advanced or metastatic breast cancer.

 

Arimidex [Anastrozole] is indicated for the treatment ofadvanced breast cancer in postmenopausal women with disease progression followingtamoxifen therapy. Patients with ER-negative disease and patients, who did notrespond to previous tamoxifen therapy, rarely responded to Arimidex[Anastrozole].

 

Apart from these uses it has also been used as an off labeldrug in the treatment of growth disorder affected children to stop or slow theonset of puberty.

 

In males, Arimidex has proven effective in the off-label useof reducing estrogens (in particular and more importantly, estradiol). Hencecan be used in selective cases of benign prostatic hyperplasia, gynecomastia,and symptoms of hypogonadism

 

Usage:

-       One tablet[1mg] to be taken once daily

-       If the dose ismissed, it is to be taken one as soon as possible provided that more than 12hours are left before the next dose is due

-       In case thedose is missed and if less than 12 hours are left before the next dose is duethen do not take the missed dose.

 

Contraindication:

Contraindicated for any patient who is hypersensitive toArimidex [Anastrozole] or to any of the excipients.

 

Warning:

 

- Pregnancy:  PREGNANCY CATEGORY D

Arimidex [Anastrozole] can cause fetal damage ifadministered to pregnant women since it can cross the placenta. There isincreased incidence of delayed fetal development like incomplete ossificationor decreased fetal weight.

In case Arimidex is administered to a pregnant woman or if awomen receiving Arimidex becomes pregnant then she should be apprised of thepotential hazards associated with Arimidex during pregnancy.

 

- Nursing Mothers/Lactating Mothers:

There is no evidence of Arimidex being secreted in breastmilk. There are no proper studies to substantiate the risks, if any, associatedwith the use of Arimidex, hence it should be avoided in lactating mothers.

 

-  Pediatric use:

The safety and efficacy of Arimidex in pediatric patientshave not been established.

 

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

 

- Tamoxifen should not be co-administered with Arimidex[anastrozole]

 

Side effects:

-       Hot flushes ?most common side effect

-       Vaginaldryness

-       Vaginalbleeding

-       Hair thinning

-       Anorexia

-       Diarrhea

-       Headache

-       Rash

-       Asthenia

-       Dizziness

-       Joint pain-use an analgesic to tide over the pain

-       Nausea andvomiting

-       Weakness

-       Fatigue

-       Brittle bones[osteoporosis] ? advice vitamin D and calcium supplements. Proper diet. Performbone mineral density (BMD) test regularly. Advice about quitting smoking andalcohol

-       Lymphedema:advice regarding avoiding using the affected arm for strenuous work.

 

Hepatic Impairment:

It is prudent to monitor the liver function tests in thepresence of hepatic failure since Arimidex is majorly metabolized in the liver.

 

Renal Impairment:

No dose adjustments are required for patients with renalimpairment.

 

Geriatric Usage:

No dose adjustments are required in geriatric age group.

 

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