Reviewed on 8/24/2021

What Is Exemestane and How Does It Work?

Exemestane is an antineoplastic (anticancer) agent used to treat breast cancer in postmenopausal women. Exemestane is often given to women whose cancer has progressed even after taking tamoxifen (Nolvadex, Soltamox) for 2 to 3 years.

Exemestane is available under the following different brand names: Aromasin.

Dosages of Exemestane


  • 25 mg

Dosage Considerations – Should be Given as Follows:

Postmenopausal ER-Positive Breast Cancer

  • 25 mg orally once/day; continue until tumor progression

Breast Cancer Adjuvant Treatment

  • Switch to exemestane after 2-3 years of tamoxifen treatment
  • 25 mg orally once/day; continue until tumor progression
  • Take after meals

Breast Cancer Prevention (Off-label)

  • 2013 American Society of Clinical Oncology (ASCO) guidelines suggest exemestane as an alternative to tamoxifen or raloxifene to prevent invasive breast cancer in high-risk women
  • 25 mg orally once/day for 5 years

Dosage Modifications

  • Coadministration with potent CYP3A4 inducers: 50 mg orally once/day

Dosing Considerations

  • High risk of breast cancer is defined as at least 1 breast biopsy showing lobular carcinoma in situ (LCIS) or atypical hyperplasia, 1 or more first-degree relatives with breast cancer, or a 5-year predicted risk of breast cancer greater than 1.66% (based on the modified Gail model)
  • Pediatric: Safety and efficacy not established


Skin Cancer Symptoms, Types, Images See Slideshow

What Are Side Effects Associated with Using Exemestane?

Common side effects of exemestane include:

  • Fatigue
  • Nausea
  • Hot flashes
  • Depression
  • Pain
  • Trouble sleeping (insomnia)
  • Anxiety
  • Shortness of breath
  • Dizziness
  • Headache
  • Swelling (edema)
  • Vomiting
  • Flu-like syndrome
  • Abdominal pain
  • Anorexia
  • Cough
  • High blood pressure (hypertension)
  • Constipation
  • Diarrhea
  • Hair loss
  • Joint/bone/muscle pain
  • Tiredness
  • Unusual or increased sweating
  • Upset stomach

Less common side effects of exemestane include:

Other side effects of exemestane include:

Serious side effects of exemestane include:

  • Bone fractures
  • Vaginal bleeding
  • Persistent nausea or vomiting
  • Unusual tiredness
  • Dark urine
  • Yellowing eyes or skin (jaundice)

Postmarketing side effects of exemestane reported include:

  • Immune system disorders: Hypersensitivity
  • Hepatobiliary disorders: Hepatitis including cholestatic hepatitis
  • Nervous system disorder: Numbness and tingling
  • Skin and subcutaneous tissue disorders: Acute generalized exanthematous pustulosis, hives, itching

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

What Other Drugs Interact with Exemestane?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider or pharmacist first.

Exemestane has no known severe interactions with other drugs.

Serious interactions of exemestane include:

Exemestane has moderate interactions with at least 39 different drugs.

Mild interactions of exemestane include:

  • bazedoxifene/conjugated estrogens
  • conjugated estrogens
  • conjugated estrogens, vaginal

This information does not contain all possible interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns or for more information about this medicine.

What Are Warnings and Precautions for Exemestane?


This medication contains exemestane. Do not take Aromasin if you are allergic to exemestane or any ingredients contained in this drug.

Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.


  • Hypersensitivity
  • Women who are or may become pregnant; premenopausal women

Effects of Drug Abuse

  • None

Short-Term Effects

  • See "What Are Side Effects Associated with Using Exemestane?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Exemestane?"


  • Uncontrolled high blood pressure (hypertension).
  • Do not administer with concomitant estrogens.
  • Routine assessment of 25-hydroxy vitamin D levels prior to the start of aromatase inhibitor treatment should be performed, due to the high prevalence of vitamin D deficiency in women with early breast cancer; women with vitamin D
  • deficiency should receive supplementation with vitamin D.
  • Reductions in bone mineral density (BMD), women with or at risk of osteoporosis should have their BMD formally assessed by bone densitometry at the commencement of treatment.
  • Not indicated for breast cancer in premenopausal women.
  • Advise females of reproductive potential to use effective contraception during treatment and for 1 month after final dose.
  • Based on findings in animals, male and female fertility may be impaired by treatment.

Pregnancy and Lactation

  • Do not use exemestane in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
  • Excretion of exemestane in milk is unknown; because of potential for serious adverse reactions in breastfed infants, advise women not to breastfeed during treatment and for 1 month after final dose.
Medscape. Exemestane.
RxList. Aromasin Side Effects Drug Center.

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