Aromatase Inhibitor

Anastrozole

A non-steroidal aromatase inhibitor used for hormone receptor-positive breast cancer in postmenopausal women.

Drug card

Class: Aromatase inhibitor
How it works: Blocking aromatase so androgens are no longer turned into estrogen
Used for: Early hormone receptor-positive breast cancer, after surgery
Advanced breast cancer after menopause
Lowering breast cancer risk in high-risk women
Known for: Hot flashes
Joint pain and stiffness
Bone thinning (lower bone mineral density)
Its name: -rozole means a nonsteroidal aromatase inhibitor

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Mechanism of action

How does anastrozole work?

A selective, non-steroidal inhibitor, anastrozole binds aromatase reversibly and stops adrenal androgens being converted to estrone and estradiol, so estradiol levels fall sharply after menopause. It has no measurable effect on the adrenal synthesis of cortisol or aldosterone.

Like other aromatase inhibitors: After menopause most estrogen is made by aromatase, a cytochrome P450 enzyme in many tissues that turns androgens (androstenedione, testosterone) into estrogens (estrone, estradiol). Aromatase inhibitors block this final step, cutting estrogen in the blood and the tumor and so starving hormone receptor-positive breast cancer. Anastrozole and letrozole bind reversibly; exemestane, a steroid, binds irreversibly.

Uses

What is anastrozole used for?

Early hormone receptor-positive breast cancer, after surgery
Advanced breast cancer after menopause
Lowering breast cancer risk in high-risk women

Side effects

Side effects of anastrozole

Hot flashesKnown for
Joint pain and stiffnessKnown for
Bone thinning (lower bone mineral density)Known for
Osteoporosis
Broken bones (fractures)Serious
High cholesterol
Heart events in women with ischemic heart diseaseSerious
High blood pressure
Low mood or depression
Allergic swelling of face, lips or throat (angioedema)Serious
Liver inflammation (hepatitis)Serious
Severe skin reactions with blisters or ulcersSerious

Known for marks what an exam expects you to know it for.

Watch for

Cautions and what sets it apart

For postmenopausal women: premenopausal ovaries make too much aromatase for it to block unless ovarian function is suppressed.
Bone density and cholesterol are monitored during treatment.
Not given with tamoxifen or estrogen-containing therapy, which reduce its effect.
Women with ischemic heart disease had more cardiovascular events on it than on tamoxifen.

Good to know: Compared with tamoxifen it caused fewer blood clots, less vaginal bleeding and less endometrial cancer, but more fractures and joint symptoms.

Remember it

A way to remember it

No aromatase, no estrogen, thinner bones

Blocking aromatase removes the main source of estrogen after menopause, and bone loses estrogen's protection: bone density falls and fractures rise, while tamoxifen, which acts like estrogen on bone, does not do this.

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Its name

-rozole means nonsteroidal aromatase inhibitor
Anastrozole and letrozole block aromatase, cutting the estrogen made after menopause, and treat breast cancer. Exemestane, a steroidal aromatase inactivator, lacks the stem.
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Its class

Aromatase inhibitors

Other aromatase inhibitors with a card:

Letrozole

Easily mixed up with selective estrogen receptor modulators and 5-alpha reductase inhibitors.

All about aromatase inhibitors

Sources

Checked against

Written for biofideX in plain words, after checking these references:

For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.

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Targeted therapy and the immune system

Anastrozole is one of 13 drugs practiced together here: their classes, how they work, what they treat and what they're known for.

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