Andarine S4 CAS:401900-40-1
Andarine S4’s mechanism of action is selective binding to androgen receptors. Features could include its partial agonist activity, tissue selectivity, and oral bioavailability. Applications might be medical and research, like treating muscle atrophy, but also its off-label use in bodybuilding. Benefits could be muscle preservation without significant androgenic side effects. Dosage in studies versus real-world use. Cycle length and typical protocols. Half-life is around 4-6 hours, so dosing frequency matters. PTC would involve managing any suppression of natural testosterone.
Andarine S4, codenamed AC-262,536, is a first-generation selective androgen receptor modulator (SARM) developed in the early 2000s by GTx, Inc. Initially researched for osteoporosis and muscle-wasting disorders, it selectively activates androgen receptors (AR) in bone and muscle tissue while minimizing effects on prostate and other androgen-sensitive organs. Unlike anabolic steroids, Andarine's tissue specificity and oral bioavailability positioned it as a groundbreaking experimental therapy-until clinical trials revealed unique side effects, such as transient vision changes, halting its FDA approval. Today, it remains a compound of interest in research and performance enhancement circles.
Structural and Functional Features
Chemical Profile
●IUPAC Name: (2S)-3-(4-acetylamino-phenoxy)-2-hydroxy-2-methyl-N-(4-nitro-3-trifluoromethyl-phenyl)-propionamide
●Molecular Formula: C₁₉H₁₈F₃N₃O₆
●Molecular Weight: 441.36 g/mol
●Solubility: Lipophilic, soluble in DMSO and PEG-400; poorly water-soluble.
Mechanism of Action
Andarine binds competitively to ARs with partial agonist activity, triggering anabolic pathways in muscle and bone while exhibiting antagonistic or neutral effects in other tissues. Key actions include:
●Myocyte Hypertrophy: Upregulates mTOR and IGF-1 signaling.
●Osteoblast Activation: Enhances bone mineral density via Wnt/β-catenin pathways.
●Selective Tissue Modulation: Sparing of prostate and sebaceous glands due to differential coactivator recruitment.
Distinctive Traits
●Oral Bioavailability: ~90% in rodent models, avoiding first-pass metabolism via nitro-group stabilization.
●Reversible Vision Effects: Dose-dependent transient yellow tinting and impaired dark adaptation (mechanism linked to retinal AR modulation).
Applications: From Lab to Lifestyle
Medical Research
1.Muscle Atrophy:
●Preserved lean mass in castration-induced atrophy models (e.g., 5 mg/kg/day in rats).
●Investigated for cancer cachexia and sarcopenia.
2.Osteoporosis:
●Increased trabecular bone density by 15% in ovariectomized rats (6-week cycles).
3.Metabolic Syndrome:
●Reduced visceral adiposity in obese Zucker rats via AR-mediated lipolysis.
Performance Enhancement
●Body Recomposition: Andarine's partial agonism promotes lean mass gains (3–5% over 8 weeks) without significant water retention.
●Cutting Cycles: Favored in pre-contest phases for muscle retention during caloric deficits.
●Stacking: Often paired with Cardarine (GW501516) to enhance fat oxidation and endurance.
Emerging Exploratory Uses
●Neuroprotection: Preclinical studies suggest AR activation may mitigate Alzheimer's-related amyloid toxicity.
●Wound Healing: Accelerates tissue repair in diabetic ulcer models.
Benefits and Limitations
Advantages
●Tissue Selectivity: Avoids prostate enlargement, virilization, and hepatotoxicity.
●Oral Efficacy: No injections required, improving compliance.
●Muscle Preservation: Effective in catabolic states (e.g., caloric restriction, aging).
Drawbacks
●Vision Disturbances: 20–30% of users report transient dyschromatopsia (yellow vision) and night blindness.
●Suppression Risk: Doses >50 mg/day suppress LH/FSH, reducing endogenous testosterone by 40–60%.
●Limited Human Data: Most safety profiles extrapolated from rodents.
Dosage and Administration
Research Protocols
●Rodent Studies: 1–10 mg/kg/day, orally, for 4–12 weeks.
●Primates: 0.5–3 mg/kg/day, showing linear pharmacokinetics.
Human Anecdotal Use
●Beginner: 25 mg/day (split into two doses, 8–12 hours apart).
●Advanced: 50–75 mg/day, though vision side effects escalate.
●Cycle Length: 6–8 weeks, followed by 4–6 weeks off.
Note: Bioavailability drops 30% with high-fat meals; administer on an empty stomach.
Cycle Design and Synergies
Standalone Cycle
●Weeks 1–8: 25–50 mg/day oral administration.
●Post-Cycle Therapy (PCT): Optional SERMs (e.g., 10 mg Tamoxifen/day for 2 weeks) if suppression symptoms arise.
Stacking Strategies
1.Andarine + Ostarine (MK-2866):
●Synergistic muscle preservation (50 mg S4 + 20 mg MK-2866).
2.Andarine + Cardarine:
●Targets fat loss and endurance (50 mg S4 + 20 mg GW501516).
3.Triple Stack (S4 + Ligandrol + Ibutamoren):
●Aggressive mass-building (50 mg S4 + 10 mg LGD-4033 + 25 mg MK-677).
Pharmacokinetics and Half-Life
●Absorption: Peak plasma concentrations at 1–2 hours post-dose.
●Half-Life: ~4–6 hours, necessitating split dosing.
●Metabolism: Hepatic CYP3A4 oxidation into inactive metabolites (e.g., deacetylated form).
●Excretion: Renal (60%) and fecal (40%).
Note: Genetic polymorphisms in CYP3A4 may alter clearance rates by up to 300%.
Post-Treatment Considerations (PTC)
●Hormonal Recovery: LH/FSH rebound within 2–4 weeks post-cycle; monitor via serum testosterone assays.
●Vision Monitoring: Ophthalmologic exams if dyschromatopsia persists >72 hours post-cessation.
●Liver Enzyme Check: Mild ALT/AST elevations possible; self-resolving in most cases.
Novel Insights and Controversies
Retinal AR Dynamics
Andarine's vision effects arise from ARβ isoform activation in retinal Müller cells, altering photopigment synthesis. Paradoxically, low doses (10 mg/day) are being studied for color vision enhancement in tetrachromacy carriers.
Epigenetic Modulation
Andarine upregulates AR-dependent miRNAs (e.g., miR-27a), suppressing myostatin expression-a mechanism absent in traditional steroids.
Ethical and Legal Landscape
●WADA Status: Banned since 2008 as a performance-enhancing agent.
●Research Chemical Loophole: Sold as "not for human consumption" to bypass FDA oversight.
Risk Mitigation and Best Practices
●Dose Titration: Start at 12.5 mg/day to assess vision tolerance.
●Cycle Breaks: Limit use to 8 weeks/year to minimize AR desensitization.
●Nutrient Support: Lutein/zeaxanthin supplements to counteract ocular stress.
Future Directions
●Prodrug Development: Esterified analogs (e.g., Andarine enanthate) for prolonged half-life.
●Gene Therapy Integration: AR-targeted CRISPR delivery to enhance muscle-specific effects.
Clinical data
|
Trade names |
Acetamidoxolutamide; Androxolutamide; GTx-007; S-4 |
|
CAS |
401900-40-1 |
|
Molar mass |
441.363 |
|
MF |
C19H18F3N3O6 |
|
Purity |
Above 98% |
|
Apprarance |
Green Tablet |
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Conclusion
Andarine S4 exemplifies the promise and pitfalls of SARMs-offering targeted anabolic benefits while grappling with off-target side effects and regulatory ambiguity. Its legacy persists in shaping next-generation androgen therapies, though responsible use demands rigorous adherence to dosing and safety protocols.
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