anastrozole vs tamoxifen
Side-by-side comparison of anastrozole and tamoxifen. Data from FDA drug databases (Orange Book, NDC Directory, recalls, shortages) covering 20,000+ approved drugs, plus CMS pricing; see our methodology.
major Known Drug Interaction
7 DRUG INTERACTIONS Tamoxifen: Do not use in combination with anastrozole. No additional benefit seen over tamoxifen monotherapy ( 7.1 , 14.1 ). 7.1 Tamoxifen Co-administration of anastrozole and tamoxifen in breast cancer patients reduced anastrozole plasma concentration by 27%.
Recommendation: Do not use these two drugs at the same time. Your doctor will usually have you take only one of these medications for your treatment.
Arimidex
Nolvadex
Anastrozole is a medicine used to treat breast cancer in women after menopause. It lowers estrogen levels in the body, which can help stop the growth of cancer cells.
Tamoxifen (Soltamox) is a medicine that can treat breast cancer. It can also lower the chance of getting breast cancer in some people.
Anastrozole is used to treat breast cancer in women who have gone through menopause. It can be used as the first treatment for advanced breast cancer, or after other treatments like tamoxifen have stopped working. It is also used to lower the risk of breast cancer returning after surgery.
This medicine is used to treat breast cancer that has spread in adults. It can also be used after surgery to help prevent breast cancer from returning in adults. Tamoxifen can also lower the risk of invasive breast cancer after breast surgery and radiation for ductal carcinoma in situ (DCIS). Finally, it can lower the chance of getting breast cancer in women who are at high risk.
Anastrozole belongs to a class of drugs called aromatase inhibitors. It works by blocking an enzyme called aromatase, which the body uses to make estrogen. By lowering estrogen levels, anastrozole can slow or stop the growth of breast cancer cells that need estrogen to grow.
Tamoxifen belongs to a class of drugs called Selective Estrogen Receptor Modulators (SERMs). It works by blocking the effects of estrogen in breast tissue. This can help to stop the growth of breast cancer cells.
- • Hot flashes
- • Weakness or fatigue
- • Arthritis
- • Pain
- • Joint pain
- • Hot flashes
- • Mood changes
- • Vaginal discharge
- • Vaginal bleeding
- • Nausea
- Tiredness 3,255
- Joint pain 3,157
- Feeling sick to your stomach 2,647
- Hair loss 2,536
- Loose stools 2,266
- Tiredness 391
- Feeling sick to your stomach 337
- Loose stools 274
- Joint pain 271
- Cancer getting worse 249
Anastrozole may cause heart problems in women who already have heart disease. It can also weaken your bones, so your doctor may want to check your bone density. This medicine can harm an unborn baby, so use birth control while taking it and for 3 weeks after your last dose.
Tamoxifen can cause serious and life-threatening problems, including cancer of the uterus, stroke, and blood clots in the lungs. Some cases have been fatal. Talk to your doctor about the risks and benefits of taking tamoxifen, especially if you are at high risk for breast cancer or have DCIS. For most people already diagnosed with breast cancer, the benefits of tamoxifen outweigh the risks.
Anastrozole can cause harm to an unborn baby. You should not take anastrozole if you are pregnant. Use effective birth control while taking anastrozole and for at least 3 weeks after your last dose. Do not breastfeed while taking anastrozole and for 2 weeks after the last dose.
Tamoxifen can harm an unborn baby. If you are a woman who could become pregnant, your doctor will perform a pregnancy test before you start taking tamoxifen. Use effective birth control while taking tamoxifen and for several months after your last dose. Do not breastfeed while taking this medicine.
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How to Read This anastrozole vs tamoxifen Comparison
anastrozole is classified in the Aromatase Inhibitor drug class, while tamoxifen sits within the Selective Estrogen Receptor Modulator (SERM) class. Drugs from different classes work through distinct mechanisms, so a head-to-head comparison illustrates trade-offs rather than equivalence. Both drugs are prescription-only, so a licensed provider must authorize use.
Adverse event totals above are pulled from the FDA's Adverse Event Reporting System (FAERS). For these top-ranked reactions alone, anastrozole has 13,861 submissions while tamoxifen has 1,522. Those figures reflect cumulative reporting volume, not per-patient risk, so older, widely dispensed drugs typically look worse on count alone. These two drugs have a known major interaction flagged in FDA labeling, attributed to tamoxifen lowers the amount of anastrozole in your blood, which may make the treatment less effective against cancer. research also shows that taking both drugs together provides no extra benefit compared to taking just one.. Serious warnings, pregnancy guidance, and contraindications can differ even when indications overlap.
A table cannot substitute for clinical judgment. Effectiveness, tolerability, drug-drug interactions with your other medications, kidney and liver function, pregnancy status, insurance formulary, and price all feed into a decision that only a licensed prescriber can make responsibly. Data here is sourced from FDA Structured Product Labels (SPL) and FAERS, both of which update as manufacturers and clinicians submit new information. This page is for educational purposes only, is not medical advice, and should not be used to self-switch between anastrozole and tamoxifen - always consult your physician or pharmacist first.
Important: This comparison is for informational purposes only. Drug effects vary between individuals. Always consult your doctor or pharmacist for personalized medical advice.