What Is Exemestane? Uses, Dosage, and What You Need to Know in 2026

Exemestane is a prescription medication used to treat hormone receptor-positive breast cancer in postmenopausal women. You may know it by its brand name, Aromasin. It belongs to a class of drugs called aromatase inhibitors and works by dramatically reducing the amount of estrogen in the body — cutting off the fuel that certain breast cancers need to grow. Here is everything you need to know about exemestane in 2026.

What Is Exemestane Used For?

The FDA has approved exemestane for two main indications:

1. Adjuvant treatment of early-stage ER-positive breast cancer: For postmenopausal women who have already received 2–3 years of tamoxifen therapy. Switching to exemestane completes a total of 5 consecutive years of adjuvant hormonal therapy.
2. Advanced breast cancer: For postmenopausal women with advanced or metastatic breast cancer whose disease has progressed after tamoxifen therapy.

Exemestane is also used off-label for:

• Breast cancer risk reduction (chemoprevention) in high-risk postmenopausal women — ASCO and NCCN guidelines recommend it as an alternative to tamoxifen or raloxifene for women at elevated risk
• Premenopausal women in combination with ovarian suppression (GnRH agonist or oophorectomy)
• Men with breast cancer, in combination with a GnRH agonist

What Type of Drug Is Exemestane?

Exemestane is a steroidal aromatase inhibitor — the only one of its kind currently FDA-approved for breast cancer. It belongs to the third generation of aromatase inhibitors, alongside anastrozole (Arimidex) and letrozole (Femara), though those two are nonsteroidal and work differently at the molecular level.

It is not a controlled substance. There are no DEA scheduling restrictions, and it can be prescribed by any licensed provider and called into any pharmacy.

What Is the Standard Dose of Exemestane?

The standard dose of exemestane is:

• 25 mg oral tablet, taken once daily, after a meal

Taking it with food is not optional — it's medically required. When taken with a high-fat meal, the drug is absorbed approximately 3x better than on an empty stomach. Always take it after eating.

If you are also taking a strong CYP3A4 inducer medication (such as rifampicin, phenytoin, carbamazepine, or St. John's wort), your doctor may increase your dose to 50 mg once daily after a meal.

How Long Do You Take Exemestane?

For early-stage breast cancer, exemestane is typically taken until you reach a total of 5 consecutive years of adjuvant hormonal therapy (counting tamoxifen years). Some patients take it for up to 7–10 years as extended adjuvant therapy based on their individual risk profile and oncologist recommendation.

For advanced breast cancer, exemestane is taken as long as your oncologist determines you're benefiting from the therapy and side effects are manageable.

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What Happens If You Miss a Dose?

If you miss a dose, take it as soon as you remember — as long as it's still the same day. If it's already the next day, skip the missed dose and take your next dose as scheduled. Do not double-dose to make up for a missed one.

If you're regularly missing doses or are struggling to maintain your supply, talk to your oncologist. Consistent daily dosing is important for the medication to provide its full protective benefit.

Who Should NOT Take Exemestane?

Exemestane should not be taken if you:

• Are pregnant or may become pregnant — exemestane causes fetal harm and requires a negative pregnancy test within 7 days before starting
• Are breastfeeding — it is unknown whether exemestane passes into breast milk
• Are premenopausal without ovarian suppression — exemestane is FDA-labeled for postmenopausal women; premenopausal use requires concurrent ovarian suppression
• Are taking estrogen-containing medications (HRT, birth control) — estrogen counteracts exemestane's mechanism of action
• Have a known allergy to exemestane or any ingredient in the tablet

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Key Facts About Exemestane at a Glance

• Brand name: Aromasin (by Pfizer/Pharmacia & Upjohn); generic available since ~2018
• Drug class: Steroidal aromatase inhibitor (type III, irreversible)
• FDA approved: 1999
• Controlled substance: No
• Dose: 25 mg tablet once daily with food
• Cash price: ~$29–$36 per 30-day supply with GoodRx or SingleCare discount
• Primary use: Hormone receptor-positive breast cancer in postmenopausal women

The Bottom Line

Exemestane is a proven, well-established treatment for hormone receptor-positive breast cancer. Take it at the same time each day with food, and don't stop without talking to your oncologist. If you're having trouble finding it at your pharmacy, medfinder.com can help. To understand how it works at the molecular level, read our guide How Does Exemestane Work? Mechanism of Action Explained.