Arimidex vs. Aromasin: Differences, similarities, and which one is better for you

Drug overview & main differences | Conditions treated | Efficacy | Insurance coverage and cost comparison | Side effects | Drug interactions | Warnings | FAQ

Arimidex (anastrozole) and Aromasin (exemestane) are aromatase inhibitors that work by blocking aromatase, an enzyme involved with the production of estrogens in the body. Aromatase converts androgens, such as testosterone, into the female hormone estrogen. Around 2 out of 3 breast cancers are classified as hormone receptor-positive breast cancer, meaning the growth of the cancer is heavily influenced and maintained by the amount of estrogen in the body. Estrogen can attach to estrogen receptors on breast cancer cells, which can signal the cancer cells to replicate and grow. 

Arimidex and Aromasin are brand-name hormone therapy medications that treat hormone receptor-positive breast cancer. By lowering estrogen levels in the body, these medications help slow or stop the growth of breast cancer cells. Arimidex and Aromasin can only be obtained with a prescription. 

Continue reading to learn more about the similarities and differences between Arimidex and Aromasin. 

What are the main differences between Arimidex and Aromasin?

Arimidex is the brand name for anastrozole. It was FDA approved in 1995, and it is used to treat hormone receptor-positive receptor early breast cancer in postmenopausal women. Arimidex is available as a 1 mg tablet taken once daily with or without food. The absorption of Arimidex in the body is not greatly affected by food. Arimidex is manufactured by ANI Pharmaceuticals. 

Aromasin is the brand name for exemestane. It was FDA approved in 1999, and it is used to treat hormone receptor-positive receptor early breast cancer in postmenopausal women who have already used tamoxifen for two to three years. Aromasin is available as a 25 mg tablet taken once daily after a meal. Food has been shown to help increase the absorption of Aromasin by the body. Aromasin is manufactured by Pfizer. 

Main differences between Arimidex and Aromasin
	Arimidex	Aromasin
Drug class	Aromatase inhibitor	Aromatase inhibitor
Brand/generic status	Brand and generic available	Brand and generic available
What is the generic name?	Anastrozole	Exemestane
What form(s) does the drug come in?	Oral tablet	Oral tablet
What is the standard dosage?	1 mg once daily	25 mg once daily
How long is the typical treatment?	5 to 10 years	2 to 3 years
Who typically uses the medication?	Postmenopausal women	Postmenopausal women

Conditions treated by Arimidex and Aromasin

Arimidex and Aromasin are FDA-approved adjuvant treatments for hormone receptor-positive early breast cancer. As adjuvant treatments, these medications are typically given after initial therapy, such as surgery, has been administered. 

Aromasin is FDA approved as an adjuvant breast cancer treatment after tamoxifen has been given for two to three years. Aromasin is given for two to three years following tamoxifen therapy for a total of five years of tamoxifen and Aromasin therapy. Known by the brand name, Nolvadex, tamoxifen is an estrogen modulator that binds to estrogen receptors on cancer cells so that estrogen cannot bind to the receptor and promote cancer cell growth. Arimidex is FDA approved as an adjuvant treatment right after initial therapy, such as surgery, without the use of tamoxifen first. 

Both Arimidex and Aromasin are also approved to treat advanced hormone receptor-positive breast cancer following tamoxifen therapy. Advanced breast cancer is also known as metastatic breast cancer, or cancer that has spread from the breast to the lymph nodes and other parts of the body, such as the bones, liver, and lungs. Arimidex is also FDA-approved as a first-line treatment for advanced hormone-unknown breast cancer, or breast cancer that may or may not be receptive to hormone therapy. Aromasin is not approved for advanced hormone-unknown breast cancer, although it may sometimes be used off-label for this purpose. 

Condition	Arimidex	Aromasin
Hormone receptor-positive early breast cancer	Yes	Yes
Advanced breast cancer following tamoxifen therapy	Yes	Yes
Hormone receptor-positive or hormone unknown locally advanced or metastatic breast cancer	Yes	Off-label

Is Arimidex or Aromasin more effective?

Arimidex and Aromasin are effective breast cancer treatments. The most effective breast cancer treatment will depend on a number of factors such as the individual’s response to the treatment, any side effects experienced, and the cost of treatment. A healthcare provider should be consulted to determine the best option.

Anastrozole and exemestane, the active ingredients in Arimidex and Aromasin, respectively, have been compared in head-to-head clinical trials. One study published in The Lancet Oncology compared anastrozole, exemestane, and letrozole. The study found that these aromatase inhibitors were similarly effective for treating hormone receptor-positive breast cancer. The study also found that five years of aromatase inhibitor therapy was not superior to two years of tamoxifen therapy followed by the use of an aromatase inhibitor for three years.

Another study published in the Journal of Clinical Oncology found that both aromatase inhibitors are similarly effective as adjuvant treatments for postmenopausal breast cancer. The main deciding factor between aromatase inhibitors may be the tolerability of the drugs regarding potential side effects. The same study found that exemestane could be an option for up-front adjuvant therapy for postmenopausal hormone receptor-positive breast cancer without the need for two to three years of tamoxifen treatment first. 

Coverage and cost comparison of Arimidex vs. Aromasin

Arimidex is a brand-name medication that is also available in a generic form. The generic form may be a cheaper option than the brand-name form. Arimidex is usually covered by Medicare and insurance plans. Using a generic Arimidex may help lower the cost for insured and uninsured patients to around $22. Otherwise, the average retail cost of brand-name Arimidex is nearly $500. 

Aromasin is also a brand-name medication that is available in a generic form. Most Medicare and insurance plans will help cover the cost of Aromasin. Still, it’s important to check with the plan’s policy and coverage benefits. Using a SingleCare savings card generic Aromasin could help lower the cost of the medication to approximately $38. The average retail cost of an Aromasin prescription is around $700. 

	Arimidex	Aromasin
Typically covered by insurance?	Yes	Yes
Typically covered by Medicare Part D?	Yes	Yes
Quantity	30, 1 mg tablets	30, 25 mg tablets
Typical Medicare copay	$0–$1	$0–$9
SingleCare cost	$22	$37

Common side effects of Arimidex vs. Aromasin

Arimidex and Aromasin can cause similar side effects such as hot flashes, joint pain, and muscle pain. As aromatase inhibitors, both medications can also cause decreased bone mineral density and an increased risk of osteoporosis. 

According to the FDA label, the most common side effects of Arimidex are hot flashes, weakness, joint pain, sore throat, high blood pressure, depression, nausea, rash, osteoporosis, insomnia, headache, and back pain. 

According to the FDA label, the most common side effects of Aromasin are hot flashes, fatigue, joint pain, headache, insomnia, nausea, increased appetite, and increased sweating. 

When both medications were compared in a head-to-head clinical trial, Arimidex was found to cause more effects on bone mineral density (osteoporosis), vaginal bleeding, and high cholesterol levels. Aromasin was found to cause more liver function abnormalities. 

	Arimidex		Aromasin
Side effect	Applicable?	Frequency	Applicable?	Frequency
Hot flashes	Yes	56%	Yes	55%
Joint pain	Yes	6%	Yes	7%
Muscle pain	Yes	16%	Yes	17%
Vaginal bleeding	Yes	2%	Yes	1%
Abnormal liver enzyme levels	Yes	1%	Yes	1%
Abnormal bilirubin levels	Yes	1%	Yes	2%
Osteoporosis	Yes	35%	Yes	31%
Atrial fibrillation	Yes	2%	Yes	1%

This may not be a complete list of adverse effects that can occur. Please refer to your doctor or healthcare provider to learn more.

Source: DailyMed (Arimidex), DailyMed (Aromasin)

Drug interactions of Arimidex vs. Aromasin

Arimidex should be avoided with tamoxifen. Taking tamoxifen with Arimidex can lower levels of Arimidex in the body, which could lead to decreased effectiveness of Arimidex. Aromasin does not interact with tamoxifen.

Estrogen-containing products like birth control pills or other contraceptives can decrease the effectiveness of Arimidex and Aromasin. This is due to the fact that estrogen therapies increase the levels of estrogen while Arimidex and Aromasin decrease the levels of estrogen in the body. The effects of estrogen treatment counteract the effects of aromatase inhibitors. 

Drugs that act as CYP3A4 inducers can decrease levels of Aromasin in the body, which can lead to decreased effectiveness of Aromasin. Medications that act as CYP3A4 inducers include rifampin, phenytoin, and carbamazepine. The dose of Aromasin will need to be increased if Aromasin is being taken with a CYP3A4 inducer. 

Drug	Drug class	Arimidex	Aromasin
Tamoxifen	Estrogen modulator	Yes	No
Estradiol Ethinyl estradiol Conjugated estrogens	Estrogens	Yes	Yes
St. John’s Wort Phenobarbital Phenytoin Carbamazepine Rifampin Dexamethasone	CYP3A4 inducers	No	Yes

*Consult a healthcare professional for other drug interactions

Warnings of Arimidex and Aromasin

As aromatase inhibitors, Arimidex and Aromasin have anti-estrogen effects. Estrogen helps promote bone growth. Decreased bone mineral density is a possible adverse effect of both Arimidex and Aromasin. Monitoring of the bones is needed before starting and during treatment with Arimidex or Aromasin. 

Women with pre-existing ischemic heart disease may have an increased risk of chest pain (angina) and heart attacks (myocardial infarction) while taking Arimidex. Seek immediate medical attention if you experience shortness of breath or chest pain after taking Arimidex. Arimidex may also cause increased cholesterol levels which can affect the development of heart disease. 

Vitamin D levels may need to be monitored while on Arimidex or Aromasin. Low vitamin D levels are associated with metastatic breast cancer. Vitamin D supplementation may be needed while on Arimidex or Aromasin. 

Arimidex and Aromasin can cause fetal harm. It is not recommended to take Arimidex or Aromasin while pregnant. 

Frequently asked questions about Arimidex vs. Aromasin

What is Arimidex?

Arimidex is a brand-name aromatase inhibitor. The generic name of Arimidex is anastrozole. It is FDA approved to treat hormone receptor-positive early breast cancer. It is also approved as a first-line therapy for postmenopausal women with hormone receptor-positive or hormone receptor-unknown advanced breast cancer. It is available as a 1 mg tablet taken once daily with or without food. 

What is Aromasin?

Aromasin is a brand-name aromatase inhibitor, like Arimidex. The generic name of Aromasin is exemestane. It is FDA approved to treat hormone receptor-positive early breast cancer after a treatment period of two to three years with tamoxifen. It can also treat advanced breast cancer that has not responded to tamoxifen therapy. Aromasin is available as a 25 mg tablet taken once daily after a meal. 

Are Arimidex and Aromasin the same?

Both medications work as aromatase inhibitors, meaning they block the action of the aromatase enzyme. They are both approved by the Food and Drug Administration (FDA) to treat breast cancer. However, Arimidex contains anastrozole and Aromasin contains exemestane. They also have slight differences in FDA-approved uses. Aromasin can be used to treat hormone receptor-positive breast cancer, but it’s not approved to be used up-front without two to three years of tamoxifen treatment. Arimidex is approved to treat hormone receptor-positive breast cancer up-front. 

Is Arimidex or Aromasin better?

Both are effective hormonal therapy options to treat breast cancer. Clinical trials have found that Arimidex and Aromasin are similarly effective for treating breast cancer in women who have undergone menopause. The best medication is the one that is effective and tolerated with the least amount of side effects. 

Can I use Arimidex or Aromasin while pregnant?

Arimidex and Aromasin should not be used while pregnant. These medications can cause fetal harm when administered to a pregnant woman. 

Can I use Arimidex or Aromasin with alcohol?

The use of alcohol in moderation is not known to cause an interaction with Arimidex or Aromasin. Therefore, alcohol consumption in moderation may be safe for people who are taking Arimidex or Aromasin. Still, it is important to consult a healthcare provider for medical advice to determine whether it’s safe to take Arimidex or Aromasin with alcohol. 

Does Arimidex or Aromasin cause hair loss?

Some women may experience hair loss while taking Arimidex or Aromasin. However, hair loss is usually temporary, and most women should be able to regrow their hair after discontinuing treatment with Arimidex or Aromasin.