S-23 is an investigational selective androgen receptor modulator (SARM). Developed as a potential male hormonal contraceptive. It binds to the androgen receptor more strongly than older drugs such as Andarine, and in animal studies it showed both a good ratio of anabolic to androgenic effects, and dose-dependent suppression of spermatogenesis with spontaneous recovery after cessation of treatment. This SARM can help to increase lean muscle mass and decrease fat mass. 

Those who use SARMs and SARM-like compounds commonly follow 8 week cycles for lean muscle gain and strength enhancement then take the following 8 weeks off. From 5mg to 15mg per day, split into two parts, is the recommended dosage for S-23. For optimal results, the dose can be halved and taken once in the morning and once in the evening.