Anastrozole (Arimidex) — Dosing, Cycles, Half-Life & Side Effects
Anastrozole (Arimidex) is an aromatase inhibitor with a half-life of 46 hours. Reversible aromatase inhibitor for estrogen control. This page is educational harm-reduction reference compiled from peer-reviewed literature — not medical advice, not an endorsement, not a recommendation to use. Consult a licensed clinician before any decision.
Quick Facts
| Class | Aromatase Inhibitors |
|---|---|
| Half-life | 46 hours |
| Detection window | 14 days |
| Hepatotoxicity | Low |
| Suppression | 0/10 |
| Administration | oral |
| US regulatory status | fda-approved |
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
Clinical (FDA-labelled): 1mg/day — FDA-labelled adjuvant breast-cancer dose for postmenopausal women. Not an on-cycle reference for men.
On-cycle (community-reported): 0.25-0.5mg 2x/week to EOD — community-standard estradiol management on aromatizing cycles
Rescue / acute management: 0.5mg/day short-course for acute estradiol-driven gyno symptoms; re-test E2 weekly and back off as soon as symptoms resolve.
Anastrozole is the most common AI in bodybuilding because of its predictable dose-response and reversibility. Use only when estradiol bloodwork (sensitive assay) confirms elevation — not prophylactically.
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 — pharmacokineticStacking two AIs is unnecessary and risks estrogen crash.
Recommendation: Use only one AI. Switch, dont stack.
Monitor: Estradiol
Tamoxifen (Nolvadex) + Anastrozole (Arimidex)
minor — pharmacokineticSome 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
What is the half-life of Anastrozole (Arimidex)?
Anastrozole (Arimidex) has a half-life of approximately 46 hours. Clearance estimate: 47h × 5 = 235h = 9.8 days. This figure is used to determine injection frequency (for esters) and post-cycle clearance timing.
What is the typical dose range for Anastrozole (Arimidex)?
Commonly reported ranges for Anastrozole (Arimidex): 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. These are compiled from published studies and community-reported usage — individual response varies and lower end is always preferred.
Does Anastrozole (Arimidex) suppress natural testosterone?
Anastrozole (Arimidex) causes minimal suppression of the HPTA axis (score 0/10). PCT may still be advisable depending on stack and duration.
Is Anastrozole (Arimidex) liver toxic?
Hepatotoxicity rating: Low. Non-17αα compound — liver stress is lower but still warrants periodic monitoring during a cycle.
What is Anastrozole (Arimidex) typically used for?
Anastrozole (Arimidex) is commonly used for: On-cycle estradiol management when bloodwork confirms elevation, All experience levels. Intended-use context does not imply safety — every use case carries the same underlying pharmacological risks.
Citations
- Pharmaceutical reference. 2004. Clinical pharmacology reference — Half-life approximately 46.8 hours (approximately 2 days) for anastrozole
- 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
- 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
- Brodie AM, Banks PK, et al. Aromatase inhibitors and hormone-dependent cancers. J Steroid Biochem Mol Biol. 1990. PMID: 2257237
Disclaimer
StackItSmart is an independent harm-reduction reference. The content above is compiled from peer-reviewed literature and is not medical advice, not an endorsement, and not a recommendation to use Anastrozole (Arimidex). Performance-enhancing compounds carry legal, endocrine, cardiovascular, and hepatic risks. Consult a licensed clinician before any decision. StackItSmart does not provide sourcing, procurement, or dosing prescriptions.