Anastrozole (Arimidex) — Dosing, Cycles, Half-Life & Side Effects

Quick Facts

Typical Dosing Ranges

Common dose range: On-cycle: 0.25-0.5mg 2x/week to EOD (Endocrine Society 2018, PMID: 29562364). Titrate against bloodwork — daily dosing is rarely needed. FDA-labelled breast-cancer dose (1mg/day) will crash estradiol in men on testosterone.

Cycle length: As needed

Time to steady state: ~10 days

Dose ranges are compiled from published pharmacokinetic studies and community-reported usage. Where a value is community-reported rather than clinically studied, this page and its structured data flag it. Lower end of any range is always the safer starting point.

Stacking Considerations

• No structural stacking blockers. Standard harm-reduction rules apply: minimize total androgen load, minimize oral exposure, and monitor bloodwork.

PCT Requirements

• Depot clearance estimate: ~10 days post-last-dose before SERM start (5 × apparent depot half-life of 47h).
• Never stack two SERMs. Extend a single SERM (tamoxifen OR enclomiphene/clomiphene) rather than combining.
• Use the cycle planner to generate a full protocol based on your complete stack, not this compound alone.

Side Effect Profile

• Easy to over-suppress estradiol if dosed daily — joint pain, lipid derangement, libido loss
• Joint pain at therapeutic doses
• Expensive
• Limited availability

Known Interactions

• Exemestane (Aromasin) + Anastrozole (Arimidex)

  moderate — pharmacokinetic

  Stacking two AIs is unnecessary and risks estrogen crash.

  Recommendation: Use only one AI. Switch, dont stack.

  Monitor: Estradiol

• Tamoxifen (Nolvadex) + Anastrozole (Arimidex)

  minor — pharmacokinetic

  Some research suggests anastrozole may reduce tamoxifen effectiveness.

  Recommendation: Consider aromasin with tamoxifen for PCT if AI needed.

  Monitor: Estradiol, Recovery markers

Related compounds

• Exemestane (Aromasin)

  Aromatase Inhibitors · t½ 8.9 hours in men (Mauras 2003, PMID: 14671195); 27 hours is the postmenopausal-women figure on the FDA Aromasin label and remains in the engine PK block (pk.halfLifeHours) pending a separate golden-file review.

• Letrozole

  Aromatase Inhibitors · t½ 2-4 days

• Ashwagandha

  Natural/Test Support · t½ 24 hours

• Clomiphene (Clomid)

  SERMs · t½ 5-7 days (apparent); zuclomiphene enantiomer ~30 days

Monitoring (Bloodwork & Vitals)

• Comprehensive metabolic panel (baseline, mid-cycle, post-cycle)
• Lipid panel (total cholesterol, HDL, LDL, triglycerides)
• CBC (hemoglobin, hematocrit — watch for erythrocytosis)
• Sex-hormone panel (Total T, Free T, Estradiol sensitive, SHBG, LH, FSH)
• Blood pressure (weekly self-check; flag systolic >140 or diastolic >90)

Baseline bloodwork is recommended before any cycle. Discontinue if liver enzymes exceed 3× upper limit of normal or if hematocrit exceeds 54%.

Frequently Asked Questions

Citations

1. Pharmaceutical reference. 2004. Clinical pharmacology reference — Half-life approximately 46.8 hours (approximately 2 days) for anastrozole
2. FDA Arimidex label + AI-in-men literature. 2018. J Clin Endocrinol Metab — Anastrozole terminal half-life 46.8 hours; daily or EOD dosing achieves steady-state in ~5 days
3. Handelsman DJ / Shankara-Narayana N et al.. 2022. Eur J Endocrinol — HPTA recovery median 52 weeks post-AAS; informs anastrozole on-cycle estradiol control duration rationale — AI-containing PCT regimens calibrated against extended recovery trajectories
4. Brodie AM, Banks PK, et al. Aromatase inhibitors and hormone-dependent cancers. J Steroid Biochem Mol Biol. 1990. PMID: 2257237