Anastrozole vs Primobolan
FDA Approved vs Well Studied
compatible Researched · 90% Aromatase inhibitors are compatible but typically unnecessary when primobolan makes up a significant portion of the total steroid load, since primobolan itself does not aromatize. AI use is dictated entirely by the testosterone dose in the stack. Some users find they can run higher testosterone doses alongside primobolan without needing an AI compared to testosterone alone, as the overall estrogen-to-androgen ratio remains favorable.
Molecular Data
Anastrozole Primobolan
Weight 293.37 Da 302.45 Da (base)
Half-life ~40-50 hours ~10 days (enanthate)
Type Nonsteroidal aromatase inhibitor (triazole derivative) DHT-derivative steroid (C20H30O2)
Key Benefits
Anastrozole
01 Potent reduction of circulating estradiol levels (70-80% at standard dose)
02 Prevents gynecomastia during testosterone or anabolic steroid cycles
03 Reduces estrogen-driven water retention and bloating
04 Helps control estrogen-related blood pressure elevation
05 Oral dosing with long half-life allows flexible scheduling (EOD or E3D)
06 Reversible inhibition allows estrogen recovery after discontinuation
07 Well-characterized pharmacokinetics with decades of clinical data
Primobolan
01 Lean muscle mass preservation during caloric deficits with minimal water retention
02 Does not aromatize to estrogen, eliminating estrogen-related side effects
03 One of the mildest androgenic profiles among anabolic steroids, with reduced risk of acne, aggression, and prostate issues
04 Injectable form is non-hepatotoxic, allowing extended cycle durations
05 Strong anti-catabolic properties through glucocorticoid receptor modulation
06 Immune-enhancing effects at moderate therapeutic doses
07 Quality, keepable muscle gains without the bloated appearance common with aromatizing steroids
08 Compatible with long cycle lengths (16-20 weeks) due to mild overall impact on health markers
Dosing Protocols
Anastrozole
0.25-0.5mg EOD or E3D (estrogen management) / Every other day to every 3 days (cycle support); daily (breast cancer)
Primobolan
400-800 mg/week (injectable) or 50-100 mg/day (oral) / 1-2x per week (enanthate) or daily (oral acetate)
Lean Mass Preservation - Cutting 400-600 mg/week 2x per week (split dose)
Lean Bulking 600-800 mg/week 2x per week (split dose)
Female Protocol 50-100 mg/week 1x per week
Side Effects
Anastrozole
Joint pain, stiffness, or dryness (from reduced estrogen-mediated joint lubrication)
Hot flashes or flushing
Fatigue and general malaise
Mood changes (flat affect, irritability, or low mood)
Decreased libido (when estrogen is suppressed too aggressively)
Headache
Primobolan
Suppression of natural testosterone production (dose-dependent, less suppressive than many other anabolic steroids but still significant)
Hair thinning or accelerated male pattern baldness (DHT derivative -- this is the most commonly reported side effect in susceptible individuals)
Adverse lipid changes, particularly HDL suppression (moderate compared to other anabolic steroids)
Mild acne or oily skin (less pronounced than testosterone or other androgens)
Injection site discomfort from larger oil volumes required at performance doses
Gradual decline in natural testosterone production requiring post-cycle therapy
Contraindications
Known hypersensitivity to anastrozole or any excipients
Premenopausal women (not indicated and potentially harmful to reproductive function)
Pregnancy or breastfeeding (teratogenic risk)
Severe hepatic impairment
Pre-existing severe osteoporosis or high fracture risk
Concurrent use with tamoxifen or estrogen-containing therapies
Prostate cancer (active or history of hormone-sensitive prostate cancer)
Breast cancer in males or females
Pregnancy or potential for pregnancy (teratogenic risk -- fetal virilization)
Severe hepatic impairment (particularly relevant for oral acetate form)
Known hypersensitivity to metenolone or formulation components
Hypercalcemia
Polycythemia (hematocrit above 54% at baseline)
Uncontrolled cardiovascular disease or severe dyslipidemia
Research Evidence
Anastrozole Primobolan
Status FDA Approved Well Studied
References 5 studies 4 studies
Latest — January 2017
FDA Approved Yes No
More comparisons: Testosterone
This comparison is for educational and research purposes only. Consult a healthcare professional before use.