SARMSARMNon-steroidalOral

Andarine (S-4)

Also known as S-4 · S4 · GTx-007 · Acetamidoxolutamide

Written by enwyReviewed 15 Jul 20261 sources0 comments

Andarine (S-4) is an early non-steroidal SARM studied mainly in animals for muscle and bone. Human evidence is essentially absent, so claims rest on preclinical work and anecdote. It is notable for a distinctive, reversible visual side effect (yellow tinting and night-vision problems) at higher doses, alongside the usual testosterone suppression.

01 Overview

S-4 was one of the first SARMs developed by GTx and is well characterised in rodent models for preserving muscle and bone mass, but it never advanced far in human development. Its short half-life led to frequent daily dosing in anecdotal protocols.

The compound is best known recreationally for a dose-dependent visual disturbance: users report a yellow tint to vision and difficulty adjusting to darkness, thought to arise from binding at retinal receptors. The effect is reported as reversible on cessation. As with all SARMs, andarine is unapproved, prohibited in sport, and sold only as a research chemical.

02 Mechanism

Non-steroidal androgen-receptor partial agonist selective for muscle and bone; a metabolite is thought to interact with retinal receptors, producing visual effects.

03 Dosing

Tier	Dose	Route	Notes
Light	25–50 mg/day	Oral	Anecdotal range, usually split due to short half-life.
Common	50–75 mg/day	Oral	Higher doses increase risk of visual disturbances.

Ester comparison

Ester	Half-life	Injection freq.	Testosterone by mass

04 Effects

Effect	Magnitude	Evidence
Preservation of muscle and boneRodent studies show maintenance of muscle mass and bone density after castration.		Preclinical
Muscle hardness and recompositionUsers report improved muscle definition; unsupported by human trials.		Anecdotal

05 Side effects

Effect	Severity	Frequency	Evidence
Visual disturbances (yellow tint, night-vision loss)Dose-dependent yellow tinting of vision and difficulty adapting to darkness, reported as reversible after stopping.	Moderate	Common at higher doses	Anecdotal
Testosterone suppressionSuppression of endogenous testosterone reported, consistent with androgen-receptor agonism.	Moderate	Common	Anecdotal
HDL cholesterol reductionReported reductions in HDL, as with other SARMs.	Mild	Common	Anecdotal

06 Legal status

United States

Not FDA-approved; unlawful as dietary supplement

as of

United Kingdom

Not licensed as a medicine

as of

07 References

Andarine (S-4) preclinical pharmacologyPubMed

08 Discussion0 comments

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This page is reference information, not medical advice. Doses and protocols are documented as they appear in the clinical literature and in practice — describing them is not a recommendation to use them. Countermeasures listed here are not a substitute for a physician. Legal status varies by jurisdiction and changes.