Andarine (S-4): Mechanism and Pharmacology
Andarine is a non-steroidal, orally bioavailable selective androgen receptor modulator (SARM) originally developed by GTx, Inc. as a candidate for treating muscle-wasting conditions, osteoporosis, and benign prostatic hyperplasia. Its chemical designation is S-4 (also rendered as GTx-007), and its molecular formula is C₁₉H₁₈F₃N₃O₆.
Andarine binds the androgen receptor with high affinity, producing tissue-selective agonism in skeletal muscle and bone while exerting only partial agonism in the prostate and sebaceous tissue. This selectivity profile is what distinguishes SARMs as a compound class from classic anabolic steroids, which activate androgen receptors systemically and without discrimination. The binding affinity of Andarine for the AR is approximately 33–38% of that reported for dihydrotestosterone (DHT), yet the downstream anabolic signalling in muscle tissue remains functionally robust at moderate doses.
The compound is metabolised hepatically via the cytochrome P450 pathway, primarily CYP3A4, with secondary involvement of CYP1A1. Oral bioavailability is estimated at roughly 60–70% in preclinical models, making tablet delivery an efficient administration route. Plasma half-life in human pharmacokinetic studies sits in the range of 4–8 hours, which has practical implications for dosing frequency: many experienced users split their daily intake into two administrations to maintain more stable blood-plasma concentrations and moderate the accumulation of active metabolites.
One frequently discussed pharmacological peculiarity of Andarine involves a reversible visual side effect — a transient yellowish tint to vision, particularly under low-light conditions — attributed to partial binding of S-4 metabolites to the ocular androgen receptor. This effect is dose-dependent and resolves following cessation or dose reduction, underlining the importance of conservative, graduated dosing protocols.
Endogenous testosterone suppression is a real consideration. Unlike fully non-androgenic research compounds, Andarine does suppress the hypothalamic–pituitary–gonadal (HPG) axis in a dose-dependent manner, though the degree of suppression is generally considered milder than that produced by exogenous testosterone or 19-nor androgens. This positions Andarine as a compound where a standard post-cycle recovery protocol remains prudent.
Application Context and User Groups
Within the bodybuilding and physique community, Andarine has carved a specific niche. Researchers and advanced recreational users most commonly associate S-4 with two primary application windows: lean recomposition phases and contest preparation cutting cycles.
During a caloric deficit, androgenic tone in muscle tissue typically diminishes as endogenous testosterone falls. Andarine's AR agonism in skeletal muscle helps preserve contractile protein content — particularly myosin heavy-chain isoforms — under hypocaloric conditions. Preclinical data from rodent models consistently demonstrated statistically significant preservation of lean mass at doses between 1–10 mg/kg, with dose-response linearity observed up to approximately 25 mg/kg before diminishing returns appeared in muscle parameters. Although direct extrapolation to human equivalents requires caution, these figures provide a useful mechanistic anchor.
Bone mineral density is a secondary benefit documented in several GTx preclinical studies. Andarine increased femoral bone density in ovariectomised rat models at doses that produced only modest changes in prostate weight — a data point that underscores the compound's tissue selectivity and its original therapeutic rationale.
User groups that typically research Andarine include:
Physique athletes approaching contest preparation — where preservation of hard-earned muscle during aggressive caloric restriction is paramount. S-4's lack of aromatisation means oestrogen-related water retention is not a confounding variable, which appeals to athletes seeking dry, striated conditioning.
Intermediate recomposition users — individuals running a moderate calorie surplus or maintenance protocol while prioritising fat oxidation alongside lean-mass accrual. Andarine does not dramatically alter body weight in the way a wet bulking compound would; instead it shifts body composition gradually, which suits those who train for aesthetics rather than raw mass.
Older male trainees concerned about bone density — the compound's documented skeletal effects make it a subject of interest among those looking to maintain both musculoskeletal integrity and muscle fullness as natural anabolic hormone levels decline with age.
It warrants a brief note that SARMs including Andarine are not approved for human therapeutic use in most jurisdictions and remain classified as research chemicals in the UK and internationally. Anyone using these compounds does so outside a clinical framework and assumes responsibility for monitoring their own health markers — including hormonal panels and liver enzymes.
Range and Selection by Concentration and Pack Size
Our Andarine category currently stocks a single, carefully chosen concentration tier: 10 mg per tablet, available in a 60-tablet pack format. This reflects the practical dosing reality for this compound, where the effective research range most commonly cited falls between 25 mg and 75 mg per day, making 10 mg tablets the logical unit for precise, flexible dosing.
Andarine (S-4) 10mg/tab 60 Tablets by Elbrus Pharmaceuticals represents the entry point and, currently, the definitive option in this group. Elbrus Pharmaceuticals is a manufacturer with a structured quality approach applied to their SARM and research compound lines, and the 10 mg tablet format is well-suited to protocols requiring incremental dose titration.
Who suits the 60-tablet / 10 mg pack?
For a researcher running 50 mg per day (five tablets daily), a single 60-tablet pack provides a 12-day supply — making it a sensible trial length to assess tolerability before committing to a fuller cycle duration. For those targeting 25–30 mg per day (two to three tablets), the same pack extends to 20–24 days, covering roughly a three-week introductory phase.
Those planning a full 6–8 week cycle at 50 mg/day would typically require three to four packs for the complete protocol, while those using lower doses for milder recomposition purposes would find two packs sufficient. The fixed 10 mg unit also enables clean dose stepping: beginning at 25 mg (2.5 tablets), moving to 50 mg (5 tablets) at week three if tolerance permits, represents a structured titration strategy that is straightforward to execute with this format.
At present, the category does not offer higher-concentration variants (e.g., 25 mg tablets), meaning users preferring fewer tablets per dose would need to consider stacking multiple tablets from the available stock. As the category expands, higher-concentration formats will be added for user convenience.
Frequently Asked Questions
What is the typical daily dose of Andarine (S-4) used in research protocols?
Most documented research protocols use Andarine in the range of 25–75 mg per day, often split into two doses to account for the compound's 4–8 hour plasma half-life. Beginners or those sensitive to the visual side effect commonly begin at 25 mg and assess tolerance before titrating upward, typically in 12.5–25 mg increments across a cycle.
Does Andarine cause testosterone suppression, and is post-cycle recovery needed?
Yes, Andarine is androgenic enough to partially suppress the hypothalamic–pituitary–gonadal axis, though generally to a lesser degree than exogenous testosterone or 19-nor compounds. A structured post-cycle period — allowing the HPG axis to normalise — is widely considered appropriate following cycles exceeding four weeks or doses above 50 mg per day. Hormonal panels before and after are advisable.
Why do some Andarine users report a yellow tint to their vision?
This visual effect is caused by reversible binding of Andarine metabolites to the androgen receptor found in ocular tissue. It manifests as a yellowish or golden hue, especially in dim lighting, and is dose-dependent. Reducing the dose or pausing use typically resolves the symptom within days to weeks. It remains the most discussed side effect unique to this compound.
Lab Tested
