Prescription medication · Aromatase Inhibitor
anastrozole
Also sold as Arimidex. Anastrozole is used to treat breast cancer in women who have gone through menopause.
Data updated 2026-05-15
- 35,161
- FDA reportsModerately reported
- 2
- InteractionsFew interactions
- 99% less
- Generic vs brandHuge savings
- $51.78
- Brand price (NADAC)
What the data shows
anastrozole (Arimidex) is a prescription Aromatase Inhibitor, reported at a middle-of-the-pack volume (35,161 FDA reports), whose generic costs a fraction of the brand (about 99% less).
Reporting volume reflects how widely a drug is used and studied, not how dangerous it is, a FAERS report documents a temporal association, never proof of cause.
anastrozole (Arimidex) is a prescription Aromatase Inhibitor. Anastrozole is used to treat breast cancer in women who have gone through menopause.
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.
Verify with FDA → · CMS NADAC pricing →
Drug Pricing (NADAC)
Brand Price
$51.78/unit
Generic Price
$0.14/unit
Generic Savings
99%
Generic Available
Yes (6 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
Anastrozole is used to treat breast cancer in women who have gone through menopause.
Common side effects
Hot flashes, Weakness or fatigue, Arthritis
Key warnings
Anastrozole may cause heart problems in women who already have heart disease.
The sections below are summarized in plain English from anastrozole's FDA-approved prescribing information. They describe what the official label says, and are not personal medical advice.
How It Works
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.
How to Take It
Take one 1 mg tablet of anastrozole once a day. You can take it with or without food. If you are taking it for advanced breast cancer, continue taking it until your tumor starts growing again. For early breast cancer, the best length of treatment is not known, but in studies, it was given for 5 years.
This is a plain-language summary of anastrozole's FDA labeling, not individualized dosing advice. Ask a pharmacist or prescriber before changing how you take this medication.
Pregnancy & Breastfeeding
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.
This is a plain-language summary of anastrozole's FDA labeling, not individualized advice. Ask a pharmacist or prescriber about pregnancy or breastfeeding on this medication.
Missed Dose
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule.
This is a plain-language summary of anastrozole's FDA labeling, not individualized advice. Ask a pharmacist or prescriber what to do about your specific missed dose.
Storage
Store anastrozole tablets at room temperature, between 68°F and 77°F, in a tightly closed container.
Side Effects (from patient reports)
Based on 35,161 FDA adverse event reports.
Most-reported reactions
Adverse reactions in FAERS for anastrozole, by number of reports
- Tiredness
Tiredness
3,255 reports
- Joint pain
Joint pain
3,157 reports
- Feeling sick to your stomach
Feeling sick to your stomach
2,647 reports
- Hair loss
Hair loss
2,536 reports
- Loose stools
Loose stools
2,266 reports
- Discomfort
Discomfort
1,773 reports
- Head pain
Head pain
1,741 reports
- Weakness
Weakness
1,569 reports
- Difficulty breathing
Difficulty breathing
1,530 reports
- Feeling lightheaded
Feeling lightheaded
1,468 reports
What this shows Bars show how often each reaction was reported, not how likely it is to happen, a report records a temporal association, never proof that the drug caused it.
Reports over time
Adverse-event reports filed for anastrozole each year to the FDA Adverse Event Reporting System (FAERS).
Year-to-year volume tracks usage, prescribing, and scrutiny, not a change in per-patient risk. Source: FDA FAERS.
Where anastrozole sits
anastrozole has more FDA adverse-event reports than 67% of the drugs FAERS tracks. A high position reflects how widely a drug is used and watched, not how dangerous it is.
Percentile across all drugs PlainMeds tracks by FAERS report volume. The dot is anastrozole; the line is the median (50th percentile).
FDA Adverse Event Report Analysis
Detailed analysis of 35,161 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2003–2025.
Total Reports
35,161
Reports Mentioning Death
2,383
6.8% of reports — not proof of cause
Hospitalization Reports
7,649
Top Indication
Breast Cancer
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | FATIGUE | 3,256 |
| 2 | ARTHRALGIA | 3,158 |
| 3 | NAUSEA | 2,648 |
| 4 | ALOPECIA | 2,537 |
| 5 | DIARRHOEA | 2,267 |
| 6 | PAIN | 1,773 |
| 7 | HEADACHE | 1,741 |
| 8 | ASTHENIA | 1,569 |
| 9 | DYSPNOEA | 1,530 |
| 10 | DIZZINESS | 1,468 |
| 11 | HOT FLUSH | 1,402 |
| 12 | PAIN IN EXTREMITY | 1,368 |
| 13 | MALIGNANT NEOPLASM PROGRESSION | 1,313 |
| 14 | MALAISE | 1,278 |
| 15 | VOMITING | 1,270 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
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.
Known Drug Interactions
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%.
Mechanism: 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.
What to do: 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.
7.3 Warfarin In a study conducted in 16 male volunteers, anastrozole did not alter the exposure (as measured by C max and AUC), and anticoagulant activity (as measured by prothrombin time, activated partial thromboplastin time, and thrombin time) of both R- and S-warfarin.
Mechanism: Research shows that this medicine does not interfere with how the blood thinner works or how much of it stays in your body.
What to do: No special changes are typically needed, but you should continue your regular blood tests as directed by your doctor.
This is a plain-language summary of interactions documented in FDA labeling, not individualized advice. Ask a pharmacist or prescriber before combining medications.
Common Questions
Can I take anastrozole if I am still having periods?
How long will I need to take anastrozole?
Can anastrozole cure my breast cancer?
Will anastrozole cause weight gain?
Can I drink alcohol while taking anastrozole?
What should I do if I have severe side effects?
Can I take other medicines with anastrozole?
Will anastrozole cause hair loss?
Does anastrozole affect my cholesterol?
What if I have liver or kidney problems?
What are the common side effects of anastrozole?
Does anastrozole interact with other medications?
What drug class is anastrozole?
Is there a generic version of anastrozole?
Is anastrozole safe during pregnancy?
Related Medications in Aromatase Inhibitor
Other drugs grouped near anastrozole - same-class peers and common alternatives.
abiraterone
Zytiga
Abiraterone (Zytiga) is a medicine used with prednisone to treat prostate cancer that has spread.
Compare with anastrozole →
bazedoxifene/conjugated estrogens
Duavee
Duavee is a combination medicine containing estrogen and a drug that blocks estrogen in some parts of the body.
Compare with anastrozole →
cabergoline
Dostinex
Cabergoline is a medicine that helps lower the amount of prolactin in your body.
Compare with anastrozole →
clomiphene
Clomid, Serophene
Clomiphene citrate is a medicine that helps women ovulate.
Compare with anastrozole →
conjugated estrogens
Premarin
Premarin Intravenous is an injectable medicine that contains estrogen hormones.
Compare with anastrozole →
Medication Guides
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Why some drugs demand precise dosing and monitoring
Common Drug Interactions
Dangerous medication combinations and how to protect yourself
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What the FDA Data Shows for anastrozole
The FDA label for anastrozole (sold under brand names such as Arimidex) classifies it as a prescription-only medication in the Aromatase Inhibitor class. Anastrozole is used to treat breast cancer in women who have gone through menopause. Official labeling lists 20 commonly reported side effects, including Hot flashes, Weakness or fatigue, Arthritis.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 35,161 voluntary reports. The database also lists 2 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated major severity. NADAC pricing from CMS shows a generic unit cost of $0.14 versus $51.78 for the brand - a 99% generic savings.
Report counts do not establish causation, a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice, always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: February 11, 2026
Read our methodology - how this data is sourced, computed, and verified.
Data currency: FDA FAERS adverse-event reports through 2025, CMS NADAC acquisition-cost pricing effective December 2024, compiled and last refreshed May 2026. See our methodology for per-source dates and refresh cadence. Spot a figure that looks wrong? Report a correction.
All federal data sources used on this page
- FDA Orange Book - approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed - NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) - post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm - standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files - federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database - current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages