Andarine (S-4) for Cutting & Body Recomposition — SARMs
First-generation SARM known for vision side effects. GTx developed. No development beyond Phase I. NOT FDA-approved.
Overview
Andarine (S-4) is a first-generation non-steroidal selective androgen receptor modulator developed by GTx Inc. as part of their SARM research program that also produced Ostarine (MK-2866). Andarine was one of the earliest SARMs to demonstrate in vivo tissue-selective anabolic activity, showing significant increases in lean body mass and bone mineral density in castrated rat models while having reduced effects on prostate weight compared to dihydrotestosterone (DHT). The compound has moderate AR binding affinity and a relatively short elimination half-life of approximately 4 hours, necessitating split dosing (2-3 times daily) for stable plasma concentrations. Andarine is most notable for its unique dose-dependent vision side effects, which include a yellow tint to vision (particularly in low-light conditions) and difficulty with night vision adaptation. These effects are caused by Andarine binding to retinal androgen receptors, and are consistently reported at doses above 50mg/day. Importantly, these visual disturbances are fully reversible upon discontinuation of the compound. Clinical development of Andarine did not progress beyond Phase I, as GTx chose to advance the more promising Ostarine through the clinical pipeline instead. Very limited published human pharmacokinetic and safety data exist. The compound demonstrates moderate anabolic potency with notable fat-reducing properties, leading to its popularity in body recomposition and cutting protocols in the bodybuilding community. Andarine is NOT FDA-approved for any indication, is prohibited by WADA, and remains an investigational compound with insufficient human safety data.
Indications
- Preclinical investigation for muscle wasting conditions
- Research into bone mineral density improvement in osteoporosis models
- Investigation of body fat reduction with lean mass preservation
- Preclinical study compound for androgen receptor selectivity research
- Research into benign prostatic hyperplasia (early preclinical, abandoned)
- Investigation of tissue-selective androgen activity mechanisms
Mechanism of Action
Andarine requires 2-3 daily doses due to ~4-hour half-life. Each dose rapidly absorbed orally. Split dosing maintains therapeutic plasma concentrations throughout the day
Dosing
| Compound | Dose | Frequency | Notes |
|---|---|---|---|
| Andarine (S-4) | 25 mg twice daily | Twice daily (split dose) | Common research protocol; vision effects uncommon at this dose |
| Andarine (S-4) | 25 mg three times daily | Three times daily | Higher dose; increased risk of vision side effects above 50mg/day total |
| Andarine (S-4) | 50 mg/day (split) | 2-3 times daily | 5-days-on/2-days-off protocol sometimes used to mitigate vision effects |
Evidence Grade
GRADE D
Safety & Contraindications
- NOT FDA-approved — clinical development discontinued at Phase I
- Dose-dependent vision disturbances — yellow tint and impaired night vision (reversible)
- Vision effects caused by AR binding in retinal tissue — unique among SARMs
- Moderate testosterone suppression at typical research doses
- Very limited human safety data — most evidence is preclinical
- Short half-life (~4hrs) requires inconvenient split dosing 2-3x daily
- WADA prohibited substance
- Gray-market product quality highly variable
- No long-term safety data in humans
- Potential hepatotoxicity — limited data but caution warranted
- Avoid driving or operating machinery if vision side effects occur