Andarine

Muscle Growth & Body Composition

Also known as: S-4, GTx-007, Acetamidoxolutamide

Selective Androgen Receptor ModulatorsResearch phase: Preclinical / Phase 1Regulatory: Not FDA-approved. WADA prohibited. Research chemical only.

Mechanism

Andarine was one of the first SARMs developed, showing strong anabolic effects on muscle and bone in preclinical studies. However, it is known for a unique visual side effect — a yellow tint to vision, especially at night — caused by off-target binding to retinal receptors. This limits its practical use.

Technical detail

Andarine (S-4) is a first-generation non-steroidal SARM developed by GTx Inc. It demonstrates partial AR agonism with anabolic activity in levator ani muscle (anabolic:androgenic ratio ~3:1 in rats). Its dose-limiting side effect is reversible visual disturbance (yellow tint, difficulty with dark adaptation) attributed to off-target binding at retinal receptors, likely related to structural similarity to certain retinal proteins. Development was deprioritized in favor of ostarine.

Evidence

Detection of the arylpropionamide-derived selective androgen receptor modulator (SARM) S-4 (Andarine) in a black-market product.
Thevis M et al. (2009) — Drug Test Anal — PMID: 20355219
PubMed-indexed analytical work confirmed andarine/S-4 in an internet-sold black-market product at roughly 150 mg/mL with a notable impurity burden, strengthening misuse and product-quality risk evidence.
moderate

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