Exemestane

Pronunciation: ex-e-mess-tain
Generic name: exemestane
Brand name: Aromasin
Dosage form: oral tablet
Drug classes: Aromatase inhibitors, Hormones / antineoplastics

Medically reviewed by Carmen Pope, BPharm. Last updated on Jul 3, 2024.

What is exemestane?

Exemestane (brand name Aromasin) is an aromatase inhibitor used to treat hormone-responsive early and advanced breast cancers in postmenopausal women.

Exemestane works by irreversibly binding to and inactivating aromatase, an enzyme needed to convert androgens (such as androstenedione from the adrenal gland and testosterone from the ovaries) into estrogen. In postmenopausal women, this is the main source of estrogen, unlike premenopausal women whose main source of estrogen is the ovaries. This cuts off the estrogen supply that breast cancer cells need to grow, reducing or preventing their growth and spread.

Exemestane (under the brand name Aromasin) was first approved by the US Food and Drug Administration (FDA) in 1999. The brand Aromasin is still available, but generic exemestane tablets have also been available for more than 10 years.

What is exemestane used for?

Exemestane is used in postmenopausal women with:

Estrogen-receptor-positive early breast cancer who have already received other treatments, including 2 to 3 years of tamoxifen, and need to switch to exemestane to complete 5 years in a row of hormonal therapy.
Advanced breast cancer whose disease has progressed despite tamoxifen treatment.

Exemestane is not for use in premenopausal women.

Exemestane side effects

The most common side effects of exemestane in women with early breast cancer include:

hot flashes/flushes (21%)
feeling tired (16%)
joint pain (15%)
headache (13%)
trouble sleeping (12%)
increased sweating (12%).

The most common side effects of exemestane in women with advanced breast cancer include:

hot flashes/flushes (13%)
feeling tired (8%)
nausea (9%)
increased sweating (4%)
increased appetite (3%).

The number of women stopping exemestane due to side effects was similar to those stopping tamoxifen due to side effects (6% vs. 5% respectively).

Serious side effects and warnings

Exemestane may cause serious side effects, including:

Bone loss. Because exemestane decreases the amount of estrogen in your body, this can reduce your bone mineral density (BMD) over time, putting you at increased risk for bone fractures or weak and brittle bones (osteoporosis). Low vitamin D levels will also contribute to bone loss. Your doctor will do blood tests to check your vitamin D level and bone density before starting treatment with exemestane and regularly throughout treatment. Women with osteoporosis or with other risk factors for osteoporosis are more at risk.

Harm to an unborn baby. Exemestane is only approved for use in postmenopausal women but if there is a risk you could become pregnant then effective contraception must be used.

Reduced fertility. Talk to your doctor if you have concerns about fertility.

Cardiac events. The incidence of cardiac events such as a heart attack or angina was reported as 1.6% with exemestane compared with 0.6% for tamoxifen.

These are not all the possible side effects of exemestane. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Who should not take exemestane?

Do not take exemestane if you are allergic to exemestane, Aromasin, or any inactive ingredients in the tablets.

Do not take exemestane if you have not yet gone through menopause, if you are pregnant, or if you are a male.

What should I tell my doctor before taking exemestane?

Before you take exemestane, tell your doctor about all your medical conditions, including if you:

are allergic to exemestane, Aromasin, or any inactive ingredients in the tablets
are still having menstrual periods (are not past menopause). Exemestane is only for women who are past menopause
have weak or brittle bones (osteoporosis)
have liver or kidney problems
are pregnant or could still become pregnant
are breastfeeding.

Pregnancy

Exemestane is for postmenopausal women only. Tell your doctor if you are pregnant or plan to become pregnant. Taking exemestane during pregnancy or within 1 month of becoming pregnant can harm your unborn baby. Females with a chance of still becoming pregnant should have a pregnancy test within 7 days before starting treatment with exemestane and use effective birth control (contraceptive) during treatment with exemestane and for 1 month after their last dose. Tell your doctor right away if you become pregnant or think you may be pregnant.

Breastfeeding

Exemestane is for postmenopausal women only. Tell your doctor if you are breastfeeding or plan to breastfeed. It is not known if exemestane passes into your breast milk. Do not breastfeed during treatment with exemestane and for 1 month after your last dose.

How should I take exemestane?

Take exemestane exactly as your healthcare provider tells you. Do not increase or decrease the dose or stop taking exemestane without talking to your healthcare provider first.

The recommended dosage of exemestane is 1 tablet (25 mg) 1 time a day.
Take it after a meal.

What happens if I miss a dose?

If you miss a dose of exemestane, take it as soon as you remember if it is within 12 hours of the missed dose. If it has been more than 12 hours, skip the missed dose and take your next dose at the usual time.

What happens if I overdose?

If you take too much exemestane, call your healthcare provider right away or go to the nearest hospital emergency room.

Exemestane dosing information

Recommended dose in postmenopausal women: Exemestane 25 mg (1 tablet) once daily after a meal.

See the prescribing information for further information about exemestane dosing.

Interactions

Tell your doctor about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements. Especially tell your doctor if you take:

estrogen-containing medicines, such as hormone replacement therapy, or birth control because these may affect how well exemestane works.
strong CYP 3A4 inducers such as rifampicin or phenytoin, because the dosage of exemestane may need to be increased to 50 mg

See the exemestane prescribing information for a full list of interactions.

Storage

Store at room temperature 68°F to 77°F (20°C to 25°C).

Keep out of the reach of children.

Exemestane ingredients

Active ingredient: exemestane

Inactive ingredients:

Aromasin brand tablets: mannitol, crospovidone, polysorbate 80, hypromellose, colloidal silicon dioxide, microcrystalline cellulose, sodium starch glycolate, magnesium stearate, simethicone, polyethylene glycol 6000, sucrose, magnesium carbonate, titanium dioxide, methylparaben, and polyvinyl alcohol.

Algoven exemestane tablets: copovidone, crospovidone, hypromellose, magnesium stearate, mannitol, polyethylene glycol 400, silicified microcrystalline cellulose, sodium starch glycolate, and titanium dioxide.

Breckenridge Pharmaceuticals exemestane tablets: colloidal silicon dioxide, crospovidone, hydroxypropyl methylcellulose, magnesium stearate, mannitol, microcrystalline cellulose, polysorbate 80, sodium starch glycolate. The tablet coating contains hypromellose, propylene glycol, and titanium dioxide.

Cipla exemestane tablets: mannitol, crospovidone, hypromellose, polysorbate 80, microcrystalline cellulose, sodium starch glycolate, colloidal silicon dioxide, magnesium stearate. The film coating contains hypromellose, titanium dioxide, and polyethylene glycol 6000.

Always check the Product Label for the exemestane tablets you take for a complete list of ingredients, because these may change.

Who makes exemestane?

Aromasin brand exemestane tablets are distributed by Pharmacia & Upjohn Company LLC, a subsidiary of Pfizer Inc.

Generic exemestane tablets are also distributed by Algoven, Inc., Breckenridge Pharmaceuticals, Cipla USA, Inc., and other companies. Inactive ingredients can vary depending on the distributor.