Anastrozole vs Letrozole: Decoding the Differences for Breast Cancer Patients
Postmenopausal women are often prescribed Anastrozole or Letrozole for treating breast cancer.
Both of these medicines belong to the class of Aromatase inhibitors and have shown their effectiveness when Tamoxifen does not work.
While there are similarities in their mechanism of action, there are some differences between Letrozole and Anastrozole.
The following article compares these two medications regarding potency, side effects, and other relevant factors to help you understand their similarities and differences.
Overview
A glance at the below table will help you summarize the difference between Anastrozole and Letrozole before we dive deep into the comparison.
| Factors | Anastrozole | Letrozole |
|---|---|---|
| Brand name | Arimidex, Altraz | Femara |
| FDA approval | 1995 | 1998 |
| Potency against Breast Cancer | Less Potent | More Potent |
| Side effects | Hot flushes, tiredness, difficulty sleeping, nausea vomiting, constipation, dizziness | Hot flashes, joint pain, muscle pain, hair loss, nausea, vomiting, constipation |
| Osteoporosis | Lower risk of osteoporosis as compared to Letrozole | Higher risk of osteoporosis as compared to Anastrozole |
| Dosage | Usual recommended dose is 1mg tablet daily | Usual recommended dose is 2.5mg tablet daily |
Anastrozole and Letrozole: An introduction
Anastrozole and Letrozole are commonly prescribed medicines for treating hormone-receptive breast cancer in postmenopausal women.
They belong to the class of Aromatase inhibitors, meaning they block the enzyme Aromatase responsible for converting Androgens into Estrogen.
This leads to a decrease in Estrogen levels which prevents the hormone from promoting the growth of breast cancer cells.
Anastrozole is also prescribed for Pubertal Gynecomastia and off-label for Endometrial cancer.
On the other hand, besides Breast Cancer, Letrozole is also prescribed for off-label use in treating infertility issues in women with PCOS.
Comparing the potency of Anastrozole and Letrozole
Potency measures the amount of medicine required to produce an effect of given intensity.
In the case of the two Aromatase inhibitors, Letrozole is highly potent in reducing the amount of Estrogen compared to Anastrozole.
A 2008 study by Geisler, Helle, et al. shows that Letrozole suppresses Estrogen to a greater degree than Anastrozole in breast tumors.
But, the potency of a medicine does not affect its efficacy.
A 2017 study showed that besides being more potent, Letrozole did not show higher efficacy when compared to Anastrozole.
Anastrozole vs Letrozole side effects
Common side effects of Anastrozole and Letrozole include hot flashes, joint pain, fatigue, and Osteoporosis (bone weakening).
But, Letrozole may cause more side effects in women with a history of weak bones.
A study reported that more women receiving Letrozole experienced Osteoporosis in the two years of receiving the therapy.
Another study on Letrozole showed that the therapy could increase Cholesterol levels in some women.
The study on Anastrozole therapy did not show high levels of Cholesterol in the patients.
However, individual experiences with side effects can vary, and some may tolerate one medication better.
Drug interactions
Anastrozole and Letrozole can interact with other medications, so informing your doctor about all the drugs you are taking is crucial.
Certain medications, such as Tamoxifen and Estrogen-containing therapies, may interfere with the effectiveness of aromatase inhibitors.
According to Drugs.com, Letrozole shows interactions with 105 drugs, while Anastrozole shows interaction with 18 drugs.
Out of these, Letrozole has three major drug interactions, while Anastrozole has only one major interaction.
The information shows that Anastrozole can be safer than Letrozole, but limited evidence proves this statement.
Hence, it is best to inform the doctor about your medical history to avoid any adverse effects of the medicine.
Conclusion
Anastrozole and Letrozole are effective aromatase inhibitors for treating hormone receptor-positive breast cancer.
While they share a common mechanism of action, differences exist in dosing, potency, potential side effects, and drug interactions.
The choice between Anastrozole and Letrozole should be made in consultation with a doctor considering individual patient factors and preferences.
Ultimately, both medications play important roles in managing breast cancer and contribute to improved patient outcomes.
Frequently Asked Questions
Is Letrozole stronger than Anastrozole?
Letrozole and Anastrozole are potent aromatase inhibitors used to treat hormone-receptive breast cancer. While Letrozole may be considered slightly more potent in reducing the Estrogen amount, the choice of medication depends on individual factors and response to treatment rather than overall strength.
Which has fewer side effects, Letrozole or Anastrozole?
Both Letrozole and Anastrozole can have side effects, but the specific side effects may vary from person to person. Some evidence shows that Letrozole may cause more side effects like bone fracture and high cholesterol levels in patients. However, It’s best to consult a healthcare provider to find the best fit for you.
Can Letrozole and Anastrozole be taken together?
More research is needed to determine if Letrozole and Anastrozole are safe to be taken together. It is best to consult an expert before taking these two medications together.
Are anastrozole and letrozole the same?
No, Anastrozole and Letrozole are two different medications belonging to the same class of medicines called Aromatase inhibitors. These medications are used in the treatment of Breast cancer in postmenopausal women.
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