Anastrozole (Arimidex)
Aromatase Inhibitor
Also known as Arimidex, adex, anastrozole
Half-life
~46-50 hours
What is Anastrozole (Arimidex)?
Non-steroidal aromatase inhibitor. Reduces estrogen conversion from testosterone.
How Anastrozole (Arimidex) works
Nonsteroidal aromatase inhibition lowers estradiol synthesis from androgen precursors.
Benefits & uses
Common uses: On-cycle estrogen control, gyno prevention, TRT management, water retention control.
Anastrozole (Arimidex) dosage
Protokol doesn't recommend doses for prescription or controlled compounds. Any figures below are reference or observational reports — dosing should be set with a qualified clinician.
- Reference range
- Very low doses used off-label (literature reports ~0.25–0.5 mg 1–2×/week); highly individual, titrated to bloodworkClinical or reference range, not a personal recommendation.
Anastrozole (Arimidex) half-life
~46-50 hours
Anastrozole (Arimidex) side effects
Crashed estrogen (joint pain, low libido, mood), cholesterol worsening, bone density loss.
- Joint pain
- Low-estrogen symptoms
- Negative bone/lipid effects if over-suppressed
- Low libido/mood if E2 crashed
- Bone density loss with over-use
- Fatigue
Warnings & monitoring
- Prescription medication — requires a doctor and estradiol monitoring. Crashing estrogen is common and harmful. Do NOT self-dose without bloodwork.
Monitoring: Requires estradiol bloodwork — over-suppression of estrogen causes joint pain, low libido, mood/bone problems.
Anastrozole (Arimidex) interactions
with Letrozole
Avoid · moderateBoth are aromatase inhibitors. Letrozole is far more potent; using together guarantees an estrogen crash.
Timing: Never combine AIs
with Letrozole
Avoid · moderateBoth are competitive aromatase inhibitors — combining them provides no additional estrogen control and risks severe estrogen crash (joint pain, low libido, depression, bone loss). Choose one AI.
Timing: Never use two aromatase inhibitors simultaneously
with Aromasin
Caution · moderateBoth suppress aromatase; stacking risks E2 crash (joint pain, low libido, depression). Cycle one or the other based on E2 bloodwork.
Timing: Choose one AI per cycle
with Nolvadex
Caution · mildAnastrozole and Nolvadex compete via overlapping estrogen pathways — Nolvadex may reduce Anastrozole's plasma levels and efficacy. Prefer Aromasin + Nolvadex if both are needed.
Timing: Minimize concurrent use; if combining, separate doses by 12 hours
with Nolvadex
Caution · moderateAnastrozole can reduce the effectiveness of tamoxifen by interfering with its metabolism (CYP enzyme competition). Use AIs during cycle, SERMs during PCT — not simultaneously.
Timing: Avoid combining AIs with SERMs during PCT — use one or the other
with Testosterone
Compatible · lowAnastrozole (Arimidex) is a standard AI on testosterone replacement therapy. Dose conservatively and based on bloodwork to avoid over-suppression of estradiol.
Timing: Arimidex dosed per bloodwork — typically 0.25–0.5mg EOD on TRT
with Testosterone
CompatibleAnastrozole (non-suicidal AI) is a standard estrogen management tool for TRT and cycles. Dosing must be calibrated to bloodwork — over-suppression of estrogen causes joint pain, libido loss, and cardiovascular risk.
Timing: Anastrozole 0.25–0.5 mg every other day alongside testosterone; adjust based on bloodwork
with Testosterone
Compatible · lowAnastrozole is a standard aromatase inhibitor used alongside testosterone to keep estradiol in range. Dose to symptoms and bloodwork — over-suppression of estrogen is a common mistake.
Timing: Take anastrozole on injection days or every other day per protocol
Commonly stacked with
Track Anastrozole (Arimidex) in Protokol.
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