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 Aug 23, 2024.

What is exemestane?

Exemestane (brand name Aromasin) is an aromatase inhibitor used to lower estrogen levels in women past menopause with early or advanced hormone-sensitive breast cancer.

Early breast cancer is cancer that has not spread outside the breast.
Advanced breast cancer is cancer that has spread to other parts of the body.

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 mechanism of action of exemestane cuts off the estrogen supply that breast cancer cells need to grow, lowering estrogen levels, and preventing the growth and spread of breast cancer cells.

Exemestane gained FDA approval on October 21, 1999, under the brand name Aromasin. Generic Aromasin is available.

What is exemestane used for?

Exemestane is used in postmenopausal women with:

Early breast cancer (cancer that has not spread outside the breast) in women who:
- have cancer that needs the female hormone estrogen to grow, and
- have had other treatments for breast cancer, and
- have taken tamoxifen for 2 to 3 years, and
- are switching to exemestane to complete 5 years in a row of hormonal therapy.
Advanced breast cancer (cancer that has spread) after treatment with tamoxifen, and it did not work or is no longer working.

Exemestane is not usually used in women who have not gone through menopause.

Exemestane is not for use in men.

Exemestane side effects

The most common side effects of exemestane are:

hot flashes/flushes
feeling tired
nausea
joint pain
headache
trouble sleeping
increased sweating
increased appetite.

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

Serious side effects and warnings

Exemestane may cause the following serious side effects.

Bone loss and decreases in bone mineral density. 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.

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.

Before taking

Do not take exemestane if you:

are allergic to exemestane, Aromasin, or any inactive ingredients in exemestane tablets.
have not yet gone through menopause, if you are pregnant, or if you are a male.

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

are still having menstrual periods (are not 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.

Exemestane is taken 1 time daily.
Take exemestane after a meal.

Exemestane dosage

Exemestane dosage for early or advanced breast cancer: exemestane 25 mg 1 time daily.

Exemestane and sun exposure

Exemestane can increase your sensitivity to sunlight and make you more prone to sunburn, even with moderate sun exposure. Avoid spending long periods in the sun.

While taking exemestane, when spending time outdoors always wear an SPF 30+ sunscreen and cover up with protective clothing, such as a long sleeve top, a hat, and sunglasses. Talk to your healthcare provider about your skin if you notice any changes such as a new mole, unusual red areas, pain, or blistering.

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.

Interactions

Tell your doctor about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements because exemestane may interact with other medications that you take. 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.

This is not a complete list of interactions. See the exemestane prescribing information for a full list of interactions.

Storage

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

Keep out of the reach of children.

Exemestane ingredients

Active ingredient: exemestane 25 mg

Inactive ingredients (depends on the manufacturer):

Aromasin exemestane 25 mg 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 25 mg tablets: copovidone, crospovidone, hypromellose, magnesium stearate, mannitol, polyethylene glycol 400, silicified microcrystalline cellulose, sodium starch glycolate, and titanium dioxide.

Breckenridge Pharmaceuticals exemestane 25 mg 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 25 mg 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 25 mg tablets you take for a complete list of ingredients, because these may change.

Who makes exemestane 25 mg?

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.