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Aromasin: 7 things you should know

Medically reviewed by Carmen Fookes, BPharm. Last updated on March 25, 2021.

1. How it works

  • Aromasin is a brand (trade) name for exemestane which is a medication that is used to treat breast cancer in postmenopausal women. It is often given to women whose cancer has progressed despite surgery, radiation, or other cancer treatments.
  • Aromasin (exemestane) works by irreversibly inactivating an enzyme called aromatase. In postmenopausal women, the principal source of circulating estrogens comes from adrenal and ovarian androgens (such as androstenedione and testosterone) which aromatase converts into estrogens (such as estrone and estradiol). Aromasin is structurally related to androstenedione, and aromatase binds to it instead of binding to naturally occurring androstenedione. This irreversibly inactivates the enzyme, which reduces circulating levels of estrogens in the body. Aromasin has no effect on adrenal biosynthesis or other enzymes involved in the steroidogenic pathway.
  • Aromasin belongs to the class of medicines known as aromatase inhibitors. It may also be called an antineoplastic hormone.

2. Upsides

  • May be used in addition to other treatments to treat estrogen-receptor positive early breast cancer in postmenopausal women who have received two to three years of tamoxifen and are switched to Aromasin to complete a total of five consecutive years of hormonal therapy.
  • May also be used to treat advanced breast cancer in postmenopausal women whose disease has progressed despite tamoxifen treatment.
  • Often given to women whose cancer has progressed despite surgery, radiation, or other cancer treatments.
  • The usual dosage is one 25mg tablet once daily after a meal.
  • Most women take Aromasin for around two to three years. Doctors may recommend some women take it for longer.
  • Studies have shown that switching to Aromasin for two to three years AFTER taking tamoxifen is better than just staying on tamoxifen for five years.
  • Aromasin significantly lowers circulating estrogen levels but has no effects on the formation of corticosteroids, aldosterone, or any other enzyme.
  • Dosage adjustment does not appear necessary in liver or kidney disease.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Common side effects include hot flashes, insomnia, headache, increased sweating, joint pain, fatigue, nausea, back or limb pain, dizziness, and high blood pressure. Visual disturbances, osteoarthritis, and depression have also been reported.
  • Other reported side effects include alopecia, abdominal pain, dermatitis, fluid retention, and muscle pain.
  • Other side effects that may occur in less than 5% of women include carpal tunnel syndrome, diarrhea, muscle cramps, nerve pain, osteoporosis, or brittle bones.
  • May not be suitable for some people including those with a known hypersensitivity to Aromasin or any of its excipients.
  • Does not work on hormone-receptor negative breast cancer.
  • May lower bone mineral density (BMD), consider monitoring.
  • Can't stop the ovaries from making estrogen, which is the principal source of estrogen in premenopausal women. However, if premenopausal women are willing to also take medication to suppress ovarian function, as well as effective nonhormonal birth control, then it may be given in certain circumstances.
  • May decrease lymphocyte counts, but the significance of this is unknown and the effect was transient.
  • Elevations in bilirubin, alkaline phosphatase or creatinine have been reported.
  • Aromasin can cause harm to a developing fetus and should not be taken by women who are already pregnant. Women taking Aromasin should not breastfeed during treatment and for at least 3 weeks following the last dose.

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

4. Bottom Line

  • Aromasin is a brand (trade) name for exemestane which is a medication that is used to treat breast cancer in postmenopausal women. It is often given to women whose cancer has progressed despite surgery, radiation, or other cancer treatments. The usual dosage is one 25mg tablet once daily after a meal and most women take Aromasin for around two to three years. Doctors may recommend some women take it for longer.

5. Tips

  • Best taken with or soon after food because it may cause nausea or indigestion. which is why it is recommended to be taken after food. If you prefer to take Aromasin without food, and you do not get nausea or indigestion from it, you can take it on an empty stomach.
  • Report any worrying side effects, such as chest pain, visual disturbances, pain, or dizziness to your doctor.
  • Be cautious when driving or operating machinery if Aromasin makes you dizzy or tired.
  • Your doctor may wish to monitor your bone mineral density (BMD) while you are taking Aromasin as it may lower your BMD. Your vitamin D levels should also be checked because there is a high prevalence of vitamin D deficiency in women with breast cancer and supplements of vitamin D should be given.
  • Do not use estrogen-containing agents while you are taking Aromasin. Tell your doctor about any medicines you take including those brought over the counter from a drug store or health shop.
  • Aromasin can cause harm to a developing fetus and should not be taken by women who are likely to become pregnant. Do not breastfeed during Aromasin treatment and for at least 4 weeks following the last dose.

6. Response and Effectiveness

  • In the FATA-GIM3 clinical trial, Aromasin 25 mg per day resulted in a 5-year disease-free survival rate of 88% (range 85.8% to 89.9%) this was not statistically different to Femara 2.5 mg per day which had a 5-year disease-free survival rate of 89.4% (range 87.3% to 91.1%).
  • 5 years of treatment with aromatase inhibitors was not superior to 2 years of tamoxifen followed by 3 years of an aromatase inhibitor.
  • The American Cancer Society also states that Femara and Aromasin work equally well in treating breast cancer.
  • Some women may decide, in conjunction with their physician, to extend aromatase inhibitor therapy for up to 10 years, particularly if they are at a higher risk for another breast cancer. As noted by the American Society of Clinical Oncology (ASCO), extending aromatase inhibitor treatment is not associated with an overall survival advantage but can lower the risk for breast cancer returning and occurring in the opposite breast, compared to no treatment (placebo). ASCO does not recommend extended treatment for longer than 10 years.
  • Aromasin and Femara showed similar effectiveness in the FATA-GIM3 clinical trial. Patient survival over 5 years was 88.0% for Aromasin and 89.4%.
  • Although food, or the lack of it, can affect the absorption rate of Aromasin, this does not translate into any differences in effect.

7. Interactions

Medicines that interact with Aromasin may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with Aromasin. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with Aromasin include:

  • antiandrogens, such as apalutamide
  • barbituates such as butabarbital
  • carbamazepine or fosphenytoin
  • dabrafenib
  • dexamethasone
  • echinacea
  • griseofulvin
  • HIV medications, such as efavirenz
  • hormones, such as conjugated estrogens, estrone, ethinyl estradiol, or hydroxyprogesterone (may interfere with its action)
  • modafinil
  • nafcillin
  • oxcarbazepine
  • phenobarbital or pentobarbital
  • rifabutin or rifampin
  • St. John's Wort
  • tacrolimus or sirolimus
  • thalidomide.

Use with strong CYP 3A4 inducers, such as rifampicin or phenytoin, decreases blood levels of Aromasin. Consider increasing the dose of Aromasin to 50mg once daily.

Note that this list is not all-inclusive and includes only common medications that may interact with Aromasin. You should refer to the prescribing information for Aromasin for a complete list of interactions.

References

Aromasin (exemestane). Updated 04/2020. Pharmacia and Upjohn Company LLC https://www.drugs.com/pro/aromasin.html

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Aromasin only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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