FDA-filed SPL labeling · retrieved through openFDA

Anastrozole

Anastrozole is an aromatase inhibitor used to treat hormone receptor-positive breast cancer in postmenopausal women — including early, locally advanced, and metastatic disease.

Brand name Arimidex
Drug class ⓘ Aromatase Inhibitor
Rx Forms 2 Route Oral
Dr. Brian Staiger, PharmD, BCPS
Reviewed by Last reviewed Jul 10, 2026
🧬 Where this information comes from Click to expand

The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 40 clinical label sets within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →

At a glance
Linked label effectiveMar 2, 2026
Clinical labels in scope ⓘ40
AvailabilityRx
Earliest approval/marketing year ⓘ1995
FDA-listed product records ⓘ126
Boxed warningNone found in compared labels
How we combine label and product data →
✓No current FDA shortage listed · checked Sep 17, 2026
⭐ Anastrozole at a glance The quick version — the full detail is in the Patient Information Guide below.
💊
HelloPharmacist Editorial Team Bottom Line
Anastrozole is an effective, once-daily oral treatment for hormone receptor-positive breast cancer in postmenopausal women, working by sharply cutting the body's estrogen production. The most important things to watch for are bone loss, joint pain, and heart health — your care team will monitor these. Never take it with tamoxifen or estrogen-containing products, and do not use it during pregnancy.
How we write & review this content — our editorial policy →

📖 Anastrozole: Patient Information Guide

A plain-language walkthrough of Anastrozole — what it treats, how it works, how it’s taken, side effects, warnings and interactions. Tap any section to expand it.

🎯What it's used for▾

Anastrozole is an aromatase inhibitor approved for treating hormone receptor-positive breast cancer in postmenopausal women across several clinical settings.

  • Early breast cancer (adjuvant): Anastrozole and Arimidex (tablet) are each approved for postmenopausal women with hormone receptor-positive early breast cancer following primary treatment such as surgery.
  • Locally advanced or metastatic breast cancer (first-line): Anastrozole and Arimidex tablets are approved as an initial treatment for postmenopausal women with hormone receptor-positive or hormone receptor-unknown locally advanced or metastatic breast cancer.
  • Advanced breast cancer (second-line): Anastrozole and Arimidex tablets are approved for postmenopausal women with advanced breast cancer that progressed after tamoxifen therapy. Women who were estrogen receptor-negative or did not respond to tamoxifen rarely responded to anastrozole.
⚙️How it works▾

In postmenopausal women, the body makes estrogen mainly through an enzyme called aromatase, which converts other hormones (androgens) into estradiol. Many breast cancers need estrogen to grow. Anastrozole selectively blocks the aromatase enzyme, dramatically lowering estrogen levels throughout the body — including in cancer tissue itself — which can slow or stop the growth of estrogen-sensitive tumors.

Anastrozole does not affect the production of cortisol or aldosterone (the body's stress and fluid-balance hormones), so no hormone replacement is needed while you take it. It also has no direct effect on thyroid hormone levels.

💊How it's taken▾

Anastrozole tablets are taken once daily by mouth and can be taken with or without food — though food may slightly delay how quickly it is absorbed. For advanced breast cancer, treatment continues until the cancer progresses; for early breast cancer, your prescriber will determine the duration (in clinical trials, treatment was given for five years).

  • No dose adjustment is needed for kidney impairment or older age.
  • No dose adjustment is needed for mild-to-moderate liver disease; severe liver impairment has not been studied.
  • Always follow your prescriber's instructions for your specific situation.
🤒Side effects — in detail▾

The most commonly reported side effects of anastrozole include:

  • Hot flashes
  • Joint pain, arthritis, or stiffness (musculoskeletal events are among the most frequent)
  • Fatigue or weakness
  • Nausea or vomiting
  • Headache
  • Bone loss (osteoporosis) and increased risk of fractures
  • High blood pressure
  • Depression, insomnia, or mood changes
  • Swelling (peripheral edema or lymphedema)

Rarely (in fewer than 1 in 10,000 patients), serious reactions can occur: severe skin blistering or ulcers, significant allergic reactions with face or throat swelling, and liver function abnormalities with yellowing of the skin or eyes. Seek immediate medical attention if any of these occur.

⚠️Warnings & precautions▾
  • Bone loss: Anastrozole reduces estrogen, which can decrease bone density and raise fracture risk — especially of the spine, hip, and wrist. Bone monitoring and protective measures (calcium, vitamin D, or bisphosphonates) may be recommended.
  • Heart health: In women with pre-existing ischemic heart disease (reduced blood flow to the heart), anastrozole was associated with a higher rate of cardiac events compared to tamoxifen. Discuss your heart history with your doctor before starting.
  • Cholesterol: Anastrozole may raise total cholesterol in some patients. Your doctor may monitor your lipid levels during treatment.
  • Pregnancy: Anastrozole can seriously harm a developing baby. Women who could become pregnant must use effective contraception during treatment and for at least 3 weeks after the last dose. Do not breastfeed during treatment or for 2 weeks after stopping.
  • Serious allergic reactions: Stop anastrozole and get emergency care if you develop swelling of the face, lips, tongue, or throat, or have difficulty breathing.
🔀What it interacts with▾

Anastrozole has a few important drug interactions to be aware of:

  • Tamoxifen: Do not take these two drugs together. Combining them reduces anastrozole's blood levels and provides no added benefit over tamoxifen alone.
  • Estrogen-containing products (e.g., hormone replacement therapy, estrogen pills or patches): These can directly counteract anastrozole's cancer-fighting action and should be avoided.
  • Warfarin: Anastrozole does not appear to meaningfully alter warfarin's levels or anticoagulant effect, but always inform your prescriber and pharmacist of all medications you take.
  • Cytochrome P450 enzyme interactions: Based on lab and human studies, anastrozole is unlikely to significantly affect other drugs through liver enzyme pathways at the standard dose.

This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.

📋Before taking it▾
  • Pregnancy: Anastrozole must not be used during pregnancy — it can cause serious harm or loss of the pregnancy. Pregnancy status should be confirmed before starting treatment in women of reproductive potential.
  • Premenopausal women: Anastrozole is contraindicated in premenopausal women, including those who are or may become pregnant — it offers no clinical benefit and poses fetal risk.
  • Breastfeeding: Do not breastfeed while taking anastrozole or for 2 weeks after the last dose.
  • Allergy: Do not take anastrozole if you have had a hypersensitivity reaction (such as anaphylaxis, severe swelling, or hives) to anastrozole or any of its ingredients.
  • Heart disease: Women with pre-existing ischemic heart disease should discuss risks carefully with their doctor before starting.
  • Liver impairment: Mild-to-moderate liver disease does not require a dose change; severe liver impairment has not been studied.
  • Kidney impairment: No dose adjustment is needed, even with significant kidney disease.
  • Children and adolescents: Anastrozole's efficacy has not been demonstrated for adolescent boys with gynecomastia or girls with McCune-Albright Syndrome; it is not a proven treatment in these groups.
🚑If you take too much▾

No single dose of anastrozole that causes life-threatening symptoms has been identified in clinical studies. There is no specific antidote — treatment focuses on supportive care, monitoring vital signs, and managing symptoms. If an overdose is suspected, seek medical attention promptly; inducing vomiting may be considered if the person is alert, and dialysis may help since anastrozole is not highly bound to blood proteins.

📡Pharmacodynamics — effects in the body▾

Anastrozole significantly lowers the amount of estradiol (the main active estrogen) circulating in the blood. At the standard daily dose, estradiol levels drop by about 70% within the first 24 hours and by roughly 80% after two weeks of consistent use. This suppression is maintained for up to six days after stopping daily dosing. Anastrozole does not affect the body's production of cortisol, aldosterone, or thyroid-stimulating hormone, meaning it does not disrupt the adrenal or thyroid systems.

🔬Pharmacokinetics — how your body processes it▾

Anastrozole is rapidly absorbed after an oral dose, reaching peak blood levels in about 2 hours on an empty stomach (food delays this to about 5 hours but does not reduce the total amount absorbed). It has a long half-life of approximately 50 hours, meaning it stays active in the body for several days — blood levels reach a stable, steady state after about 7 days of once-daily dosing. The drug is broken down mainly by the liver (about 85% of elimination), with a small portion removed by the kidneys; no dose adjustment is needed for kidney or mild-to-moderate liver impairment.

📦How to store it▾

Store at controlled room temperature, 20° to 25°C (68° to 77°F) . Dispense in a tight, light-resistant container as defined in the USP, with a child-resistant closure (as required).

📄 Written from Anastrozole’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Every point is grounded in that labeling — nothing is invented. How we use AI →

22

Supplements & herbs that interact with Anastrozole

22 supplements and herbal products have documented interactions with Anastrozole in the licensed clinical database we use. Most are manageable — but your pharmacist should know about everything you take, including vitamins and herbals.

Severity mix
  • Major · 1
  • Moderate · 12
  • Minor · 9
ACTIVATED CHARCOAL Major 7-METHOXYFLAVONE Moderate ARIMISTANE Moderate ATRACTYLODES Moderate CHRYSIN Moderate COFFEE CHARCOAL Moderate DHEA Moderate EUROPEAN MANDRAKE Moderate +14 more
Every supplement checked against Anastrozole — ranked by severity The full interaction hub: 1 major · 12 moderate · 9 minor · every one linked to its full report. Check Anastrozole against your exact supplements

Educational information from a licensed clinical database (Natural Medicines) — see our data sources & update cadence. Not medical advice: an interaction being documented does not mean it will happen to you; do not start or stop medications or supplements without professional guidance.

🩺 Pharmacist Counseling Corner

Quick, plain-English answers to the questions patients ask most about Anastrozole — the kind of thing our pharmacy team would talk through with you at the counter.

What exactly is anastrozole doing in my body to fight breast cancer? ▾
Great question. After menopause, your body still makes small amounts of estrogen through an enzyme called aromatase — and many breast cancers use that estrogen as fuel to grow. Anastrozole blocks this enzyme very specifically, which dramatically lowers the estrogen levels in your body and starves estrogen-sensitive cancer cells. It doesn't affect your other important hormones like cortisol, so you won't need any extra hormone replacements while you're on it.
Can I take anastrozole with food, or does it have to be on an empty stomach? ▾
You can take it either way — with or without food. Food does slow down how quickly your body absorbs it, but the total amount that gets into your system stays the same. Pick whatever is most comfortable and easiest for you to remember, and try to take it at the same time each day.
My joints have been really achy since I started anastrozole. Is that normal, and will it go away? ▾
Yes, joint pain and stiffness are one of the most common side effects and are directly related to how anastrozole lowers estrogen. Estrogen helps protect joints, so lower levels can lead to discomfort. It doesn't go away for everyone, but many people find it manageable. Let your doctor know how you're feeling — they may have strategies to help, and it's important not to stop the medication without talking to them first, since the treatment is doing important work.
I heard anastrozole can weaken my bones. What should I be doing about that? ▾
This is a real concern worth taking seriously. Because anastrozole lowers estrogen, it can gradually reduce bone density and raise the risk of fractures, particularly of the spine, hip, and wrist. Your doctor may recommend getting bone density scans, taking calcium and vitamin D, and possibly a bone-strengthening medication. Don't wait for a fracture — ask your care team about a bone protection plan when you start treatment.
Can I take anastrozole with tamoxifen or with my hormone replacement therapy? ▾
No to both. Taking anastrozole with tamoxifen at the same time was studied and actually reduced anastrozole's effectiveness without providing any extra benefit, so those two should not be combined. Similarly, any estrogen-containing product — including hormone replacement patches, pills, or creams — can directly counteract what anastrozole is trying to do. Make sure your entire care team knows every medication and supplement you're taking.
Is anastrozole safe to take if I'm thinking about becoming pregnant or if I'm breastfeeding? ▾
Anastrozole should not be taken during pregnancy — it is known to cause serious harm to a developing baby and can lead to pregnancy loss. If you are of childbearing age, you must use reliable birth control during treatment and for at least 3 weeks after your last dose. You should also not breastfeed while on anastrozole or for 2 weeks after stopping. If there is any chance you could be pregnant, tell your doctor before starting. This drug is designed for postmenopausal women, so it's worth a direct conversation if your situation is different.
Is Anastrozole available over the counter? ▾
Anastrozole is dispensed by prescription according to its FDA labeling, so it isn't sold over the counter. Your prescriber and pharmacist will determine if it's appropriate for you.
When was Anastrozole first available? ▾
Anastrozole has been available in the United States since at least 1995, based on FDA approval history (Drugs@FDA) and product marketing records.
Who makes Anastrozole? ▾
Anastrozole is supplied by 49 manufacturers listed in the FDA NDC Directory, including PD-Rx Pharmaceuticals, Inc., NuCare Pharmaceuticals,Inc., Bryant Ranch Prepack.

💬 Answers drafted from Anastrozole’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Grounded in that labeling — nothing is made up. How we use AI →

🧰 Keep exploring

📊Anastrozole supplement interactions22 checked — ranked by severity 🌿Drug & Supplement CheckerAnastrozole vs. vitamins & herbs 💬Ask a PharmacistFree answer, usually < 24h 🔎NDC & pricing lookupFind Anastrozole NDCs & costs 🅰️Browse Drugs A–ZLook up any medication

💊 How Anastrozole comes

Anastrozole is available in 2 forms. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.

Tablet

By mouth
Brands Arimidex
How this form is used
What it may be used for
  • Arimidex (tablet) is used for adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer
  • Arimidex (tablet) is used as first-line treatment of postmenopausal women with hormone receptor-positive or hormone receptor-unknown locally advanced or metastatic breast cancer
  • Arimidex (tablet) is used for advanced breast cancer in postmenopausal women whose disease progressed after tamoxifen therapy
  • Anastrozole (tablet) is indicated for the same three breast cancer uses as Arimidex in postmenopausal women
Important instructions
  • Arimidex and Anastrozole tablets are each taken once daily by mouth
  • Both Arimidex and Anastrozole tablets may be taken with or without food
  • For advanced breast cancer, Arimidex and Anastrozole tablets should be continued until tumor progression, as directed by your prescriber
  • No dose adjustment is needed for kidney problems or older age; patients with mild-to-moderate liver disease also require no dose change
Available strengths 1 strength
1 mg
100 FDA-listed product records ⓘ

Oral suspension

By mouth
Available strengths 1 strength
1 kg/kg
1 FDA-listed product record ⓘ

📊 Anastrozole across the U.S. market

How Anastrozole appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.

2
Dose forms ⓘ
49
Manufacturers
2
Brand names
126
FDA-listed product records ⓘ
1995
First marketed ⓘ

FDA-listed product records by dose form (tablet variants merged) — FDA National Drug Code Directory. Record counts are not sales or prescription volume.

Also listed with the FDA, not a patient dose form: Powder (25) — bulk drug substance sold to compounders/manufacturers and multi-item kits. These aren’t counted in the dose-form total above.

PD-Rx Pharmaceuticals, Inc.10%
NuCare Pharmaceuticals,Inc.9%
Bryant Ranch Prepack7%
A-S Medication Solutions6%
Excella GmbH & Co. KG5%
AvKARE4%
Other makers58%

Share of FDA-listed product records by manufacturer — FDA National Drug Code Directory. Record counts are not sales or prescription volume.

📈 How widely Anastrozole is used

A general measure of how commonly Anastrozole is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.

Think of this as a proxy for how widely Anastrozole is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.

219,033
Medicaid prescriptions filled (Q1–Q4 2025)
$3.2M gross Medicaid reimbursement (before mandatory rebates — net cost is lower)

How commonly is Anastrozole prescribed? Of the 1,596 medications we measure, Anastrozole ranks #378 by Medicaid prescriptions — more than 76% of them.

Where Anastrozole ranks among the drugs we measure · Q1–Q4 2025 · neighbors ±5
Total prescriptions — #378 of 1,596
#373 Cefazolin 230,732 Rx #374 Thyroid 228,962 Rx #375 Eszopiclone 227,706 Rx #376 Metronidazole Topical 224,112 Rx #377 Simethicone 219,250 Rx #378 Anastrozole 219,033 Rx #379 Permethrin Topical 217,112 Rx #380 Moxifloxacin Ophthalmi... 215,639 Rx #381 Aflibercept Injection 214,860 Rx #382 Cefuroxime 214,273 Rx #383 Sevelamer 212,246 Rx

Utilization by Anastrozole product

Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.

anastrozole 1 MG Oral Tablet

219,033 Medicaid prescriptions (Q1–Q4 2025) 100% of Anastrozole prescriptions shown $3.2M gross reimbursement (before rebates) ≈ $14 per prescription (gross)

Summed across the 17 of 127 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 199224

Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.

Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Anastrozole, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 17 of 127 listed Anastrozole NDCs with Medicaid activity.

🔍 Compare Anastrozole products

A representative set of FDA-listed product records for Anastrozole — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)

Showing 126 of 126 products — FDA National Drug Code Directory. See every product, package size and price: browse all 126 Anastrozole NDCs →

RxNorm Concept Web — From Ingredient to Every Form and Strength

This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.

Ingredient (IN) Anastrozole RxCUI 84857 1 dose form · 1 strength
  1. Dose form (SCDF) Oral Tablet RxCUI 370588 In current FDA listings
    Clinical drug / strength (SCD) 1 MG RxCUI 199224

Look up RxCUI 84857 in the RxCUI Atlas →

RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.

🏷️ Sold under these brand names

Arimidex

🏭 Manufacturers & labelers

PD-Rx Pharmaceuticals, Inc. 12 NuCare Pharmaceuticals,Inc. 11 Bryant Ranch Prepack 8 A-S Medication Solutions 7 Excella GmbH & Co. KG 6 AvKARE 5 Breckenridge Pharmaceutical, Inc. 5 Accord Healthcare Inc. 3 Teva Pharmaceuticals USA, Inc. 3 Yiling Pharmaceutical, Inc. 3 Proficient Rx LP 3 Zydus Pharmaceuticals USA Inc. 3 Direct_Rx 3 Chartwell RX, LLC 3 American Health Packaging 3 ANI Pharmaceuticals, Inc. 3 AvPAK 3 BluePoint Laboratories 3 NuCare Pharmaceuticals, Inc. 2 Zydus Lifesciences Limited 2 Remedyrepack Inc. 2 Asclemed USA, Inc. 2 Aurobindo Pharma Limited 2 Natco Pharma Limited 2

…and 16 more on the FDA NDC directory.

RxNorm drug class

Anastrozole belongs to the Aromatase Inhibitor class.

Pharmacologic class Aromatase Inhibitor
Drug family (ATC) Aromatase inhibitors
How it works Aromatase Inhibitors

Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.

🔬 Where this comes from

Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.

📄
FDA-filed drug labels (SPL) Uses, dosing, warnings & side effects from SPL records retrieved through openFDA; the linked representative set can be verified on DailyMed. ✓ Linked label effective Mar 2, 2026
🏭
Forms, brands & labelersAggregated from ingredient-matched FDA National Drug Code Directory product records for Anastrozole.
📈
Real-world reportsThe FDA Adverse Event Reporting System (FAERS), served through openFDA.
🚨
Recalls & shortagesopenFDA drug-enforcement reports and the FDA drug-shortage database.
🧾 Clinical label set — FDA-filed SPL labels retained for Anastrozole after exact ingredient or ingredient-combination matching and applicable route/form matching
Clinical labels in scope
40
NDC products indexed
126
Distinct labelers/manufacturers represented
49
Linked representative label ⓘ
ANI Pharmaceuticals, Inc.
Linked label effective
Mar 2, 2026
Composite sections available
23
Linked SPL Set ID
acbfaaa9-503c-4691-9828-76a7146ed6de
Linked SPL Document ID
e8849657-0444-4ca8-bf66-2017f60d5652
Open the linked representative label on DailyMed ↗

How we combine label and product data

HelloPharmacist combines public FDA and NLM records; we don’t author the underlying clinical facts. We identified 40 FDA-filed SPL label sets within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. The representative label is the starting point for the displayed reference monograph; the 12 largest stored in-scope SPL records, which may include that representative, are compared section by section, and the longest available version of each section is retained. Forms, routes, brands, labelers, product-listed strengths, and product-record counts are aggregated separately from ingredient-matched FDA NDC Directory records; package records listed above are associated with the linked SPL; and the normalized concept hierarchy comes from NLM RxNorm.

For canonical ingredient pages, bounded product-attributed indication and administration excerpts may be added to the AI evidence, and the generator is instructed to preserve available product, brand, route, and form qualifiers instead of treating one label as universal. Where a section is identified as AI-written, its plain-language text is generated from bounded label evidence. New draft drug pages remain in the admin review queue before first publication. ANI Pharmaceuticals, Inc. is the representative DailyMed label linked for verification and dates; it is not the sole source used for the page.

This is general education, not medical advice — always consult your doctor or pharmacist about your medications and any medical condition. For the exact wording of the linked representative label, view that label on DailyMed; some displayed composite sections may come from other in-scope SPL labels. Learn how we use AI and our data sources & update cadence.