Anastrozole_Dosage, benefits & legal status
Also known as Arimidex, ANA, anastrozol
An aromatase inhibitor approved for postmenopausal breast cancer.
Common vial size is what vendors typically sell, not a recommendation. Enter your own vial in the calculator.
What is Anastrozole?
Plain language first. The technical label stays, but it never stands alone.Overview
It stops the body making estrogen in the first place, so estrogen levels fall.
Anastrozole is a non-steroidal aromatase inhibitor that blocks the enzyme converting androgens into estrogen, lowering circulating estrogen rather than blocking its receptor.
What it's used for
A breast cancer drug used on the research market to hold estrogen down during a testosterone or anabolic cycle.
How does Anastrozole work?
What it does in the body, and where.Anastrozole works upstream of the receptor, on supply rather than on signal.
- 01It blocks aromataseAromatase is the enzyme that turns androgens into estrogen.
- 02Circulating estrogen fallsIn postmenopausal women almost all remaining estrogen comes through this route, which is why the drug works there.
- 03Every tissue that needed estrogen noticesBone is the clearest one. Estrogen protects bone, and the trials measured bone loss within a year.
- 04It does nothing to the receptor itselfThis is the practical difference from tamoxifen, and the reason the label says not to take the two together.
A schematic of the compound's mechanism, not a diagnostic image.
What else is it used for?
Each use below carries its own evidence level. Approved means regulators have cleared it for that purpose. Investigational means it is in trials. Early research means it is being studied and is not established.
- Hormone receptor-positive breast cancer in postmenopausal womenFDA-approved
- Holding estrogen down during testosterone therapy, off-labelClinical use
- Controlling estrogen during an anabolic cycleResearch only
The published record
Papers and trials about Anastrozole
428 papers tagged human · 289 not reviews or lab · 126 clinical trial publications
494 registered trials · 31 with posted results
Furthest stage reached: Approved in the US
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Category 1, component of an FDA-approved drugRegulatorsCounted from Europe PMC indexing, not read by a person; a human tag can land on reviews, commentary or lab papers; clinical trial publications is the narrower count. 500 papers and 100 trials indexed in detail.
At a glance
Four things to know about Anastrozole
Evidence
FDA-approved
Category
Sexual and hormonal
Common vial
Varies
Half-life
About 50 hours
How much, and do you cycle it?
The range, and whether you take breaks.1 mg per day, daily. Continuous, for years in the trials FDA label
Given daily and without a break for the duration of treatment. The intermittent twice-weekly dosing used alongside testosterone is a community pattern built around symptom control rather than anything from a trial.
About 50 hoursFDA label
Mean terminal elimination half-life in postmenopausal women. Cleared mainly by the liver, about 85 percent, with roughly 10 percent through the kidneys. In children the label reports 46.8 hours, which is close enough to be the same figure.
Source: Arimidex label, section 12 Clinical Pharmacology, Excretion
You can compare this against the whole library to see where it sits.
What does it cost?
Typical dose and cost, in plain numbers.Anastrozole is not injected
It is taken by mouth (oral). The label is a single 1 mg tablet once a day, in every approved indication. The much smaller and less frequent doses used alongside testosterone, often a fraction of a tablet twice a week, are not on the label and were never studied for that purpose.
Anastrozole starts at $64.03 across 4 vendors, typically $109.99 per mg.
5 listings, last read Oct 10, 2026. Shipping and card fees are not included.
How do you store it?
Before mixing, and after.Room temperature. Cool, dry, out of light.
Anastrozole is taken as a pill or capsule. Keep it in its original container at room temperature, away from heat, humidity, and direct sun. No fridge or mixing needed. Check the expiration date on the bottle.
What are the side effects and cautions?
Known cautions and warnings for this compound.Who should avoid it
- Pregnancy
- Existing osteoporosis or low bone density, without a plan to manage it
- Known hypersensitivity to anastrozole
- Pre-existing ischaemic heart disease, where the label notes more ischaemic events on anastrozole than on tamoxifen
- Banned in drug-tested sport
Stop and get help
- Chest pain, or new breathlessness on exertion
- A bone fracture from a minor fall or knock
- Severe joint pain that stops you using a hand or walking
- Signs of an allergic reaction such as face or throat swelling, hives, or trouble breathing
Common effects
- Joint pain and stiffness
- Hot flushes
- Fatigue
- Low mood
- Rising cholesterol
- Falling bone density over months
Where this page says nothing is established, that means nobody has studied it, not that a compound is safe.
Is Anastrozole approved?
And where the numbers on this page come from.Yes. Anastrozole is FDA approved and available on prescription in the United States.
- Approval statusFDA-approved
- RouteBy mouth (oral)
- Checked24 August 2026
- DoseFrom the drug label. The manufacturer tested this range and a regulator reviewed it.
- Vial sizeFrom what vendors typically list; not a recommendation.
- Sources
What has happened recently
First approved in the US in 1995, for hormone receptor-positive breast cancer in postmenopausal women. There is no approved use in men and none in premenopausal women. The label warns on bone mineral density and on total cholesterol, and reports that in women with pre-existing ischaemic heart disease, ischaemic cardiovascular events were more common on anastrozole than on tamoxifen. It also says not to combine it with tamoxifen, because no added benefit was seen over tamoxifen alone. Prohibited in sport at all times by WADA under section S4.
What regulators say
From official documentsProhibited at all times, in and out of competition. S4.1 Aromatase inhibitors (anastrozole named). Specified Substance.
Checked 12 September 2026WADA: The 2026 Prohibited List (in force 1 January 2026)Category 1, component of an FDA-approved drug
Checked 11 September 2026FDA: Bulk Drug Substances Nominated for Use in Compounding Under Section 503B (interim categories 1, 2, 3), updated March 21, 2025
Banned in drug-tested sport. Most research peptides are prohibited under WADA's S0 category, which covers any substance with no approval from any regulatory authority for human use. That means a compound can be banned without ever being named on the prohibited list. Check with your own anti-doping authority rather than assuming absence from the list means permitted.
You can compare this against the whole library, or read how to check a seller.
What else is like Anastrozole?
Others in Sexual and hormonal, side by side.If you're weighing Anastrozole, it's worth reading Clomiphene, Enclomiphene, and Tamoxifen in the same class.
An aromatase inhibitor approved for postmenopausal breast cancer.
- Dose
- 1 mg per day
- How often
- Daily
A fertility drug approved for women in 1967, now sold to men.
- Dose
- 50 mg per day for a 5-day course
- How often
- Once a day for five days per cycle
Half of the fertility drug Clomid, sold on its own for testosterone.
- Dose
- 12.5 up to 25 mg per day
- How often
- Daily
A breast cancer drug with a boxed warning, sold as a gyno fix.
- Dose
- 20 up to 40 mg per day
- How often
- Daily
Guides for this compound
- mcg vs mg: The Peptide Dosing Mistake to Avoid
Your vial says mg and your protocol says mcg. Here is the conversion and how to check it.
Sources
- Arimidex prescribing information, DailyMed(2024)1995 initial US approval, indications, bone and cholesterol warnings, ATAC cholesterol figures.
- Arimidex label PDF, FDA Drugs@FDA(2024)Current label text including the ischaemic heart disease warning.
Beyond these, 600 records are indexed. Browse the records