Drug Class

Aromatase inhibitors

Blocking aromatase so androgens are no longer turned into estrogen.

Also called AIs.

Class card

Drugs: Anastrozole and Letrozole
Used for: Hormone receptor-positive breast cancer after menopause
Lowering breast cancer risk after menopause
Known for: Joint pain and stiffness
Bone thinning (lower bone mineral density)
Name stems: -rozole

3 cards: the class, and each drug in it.

Mechanism of action

How do aromatase inhibitors work?

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.

The drugs

Aromatase inhibitors with a card

Uses

What are aromatase inhibitors used for?

Hormone receptor-positive breast cancer after menopause
Lowering breast cancer risk after menopause

Side effects

Side effects of aromatase inhibitors

Joint pain and stiffnessKnown for
Bone thinning (lower bone mineral density)Known for
Osteoporosis
Broken bones (fractures)Serious
Hot flashes
High cholesterol
Low mood or depression
High blood pressure
Vaginal bleeding
Swollen legs and ankles (edema)

What the class has in common. Each drug's card has its own, and Known for marks what an exam expects you to know.

Watch for

Cautions

For use after menopause: before it, the ovaries make too much aromatase to block unless ovarian function is suppressed.
Bone density and cholesterol are monitored during treatment.
Not combined with tamoxifen or estrogen-containing products, which reduce their effect.
Pregnancy: they can harm the fetus.

Remember them

A way to remember them

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.

Written for biofideX

Name stems

-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.
Every drug name stem

Don't mix them up

Classes easily confused with these

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.

Practice them

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