# Arimidex (Anastrozole)

*Also known as: Anastrozole, Adex, AI*

Non-steroidal aromatase inhibitor; used to control estradiol on-cycle. Over-suppression risk.

## Overview

Arimidex (anastrozole) is a non-steroidal aromatase inhibitor originally developed for estrogen-receptor-positive breast cancer and used off-label to control estradiol during testosterone therapy or anabolic cycles. It competitively inhibits the aromatase enzyme, reducing the conversion of androgens to estrogens and lowering circulating estradiol within roughly 24 hours of a dose. The compound has a roughly 47-hour half-life, reaches peak plasma quickly, and shows about 80% bioavailability, with steady-state estradiol suppression achievable on a small, infrequent dose schedule because of its potency. The dominant risk is over-suppression, where estradiol drops too low and drives joint pain, libido loss, lipid deterioration, and mood changes, so dosing in self-directed use is frequently lower and less frequent than the oncology label. Harm reduction centers on symptom-driven, not scheduled, dosing guided by estradiol bloodwork, avoiding stacking multiple aromatase inhibitors, and treating any joint or libido change as a prompt to retest.

## Pharmacokinetics

- **Model tier:** advanced
- **Half-life:** 1.9 days (46.8 hours)
- **Cmax:** 3930 ng/mL
- **Tmax:** 0.0 days
- **Bioavailability:** 80%

## Dosing

- **Default dose:** 0.5 mg
- **Typical range:** 0.25–1 mg
- **Units:** ng/mL

## Source

- **Label:** PubMed anastrozole PK
- **URL:** https://pubmed.ncbi.nlm.nih.gov/19470631/

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**Canonical URL:** https://anabolicdex.com/compounds/arimidex
**Plot:** https://anabolicdex.com/plot?compound=arimidex