How safe is SARM S23?

SARM 23 can be found in some webstores that sell research chemicals online. Not much is known about the working or side effects of SARMs in humans, so caution is advised. And a 2009 animal study, in which researchers at GTx tried S23 out on rats, suggests that S23 is a little more risky than other SARMS.


The full name for S23 [structural formula shown below] is (S)-N-(4-cyano-3-trifluoromethyl-phenyl)-3-(3-fluoro,4-chlorophenoxy)-2-hydroxy-2-methyl-propanamide. S23 is closely related to S22, another SARM doing the rounds on the grey market.

How safe is S23? S22 and S23, like ostarine and andarine, were developed by GTx. Companies like GTx are pinning their hopes on SARMs becoming an alternative to hormones like testosterone, so they are searching for a substance that has the desirable characteristics of testosterone, but not the less desirable characteristics.

Supplements containing Hericium erinaceus can be bought online. They usually contain 500 mg extract per capsule. The supplement is used above all as a cerebrogenic – by people looking to improve their mental capacity.

SARMs should boost muscle growth, reduce fat mass and strengthen bones – but not cause prostate enlargement or increase aggression or decrease natural testosterone production.

The search still has a long way to go, but there are already dozens of SARMs circulating in the doping world and the grey supplements market.

How safe is S23? These substances have not been made in the factories of SARMs developers, but in the factories of chemicals manufacturers in Asia. Although most SARMs are patented, these producers ignore the patents and are pushing their products on the global market.

Most of these SARMs have not yet been tested on humans, but only on rats or mice. This is also true for S23.

S23 can be taken orally, but in this experiment the researchers gave male rats daily injections of S23 for 14 days. The doses varied from 0.01 to 1 mg S23 a day. The human equivalent of these doses – for an adult male weighing 80 kg – would be somewhere between 0.5 mg and 50 mg.

The figure below shows that a dose of 0.3 mg S23 [human equivalent: 15 mg] leads to an increase in muscle mass, but that the prostate dimensions decreased.



S23 not only boosted muscle mass, but also reduced fat mass, as you can see in the figure above.

So far, S23 would seem to be good stuff for athletes. This is probably because S23 is an excellent ligand for the androgen receptor. S23 attaches itself to an androgen receptor just as easily as DHT does.

But when the researchers looked at the effect of S23 on the body’s own testosterone production, it emerged that S23 probably suppresses this heavily. The SARM definitely reduces the secretion of the hormones LH and FSH.


And S23 halts the production of sperm in the testes. In fact it does this so well that the researchers suspect S23 might be a good candidate for a male contraceptive. If this is the case it would probably have to be part of a cocktail that also contains an estradiol analogue, the researchers discovered. The lab animals lost their libido when they were given S23 on its own, and only recovered this when they were given estradiol benzoate together with the S23.

SARMs have a bit of a ‘soft’ image in the doping world. They don’t stimulate muscle growth in the way that anabolic steroids do, but many users say that they are safer. There are no studies yet that confirm this suspicion. But that S23 is not one of the safer SARMs – we’d be willing to wager a bottle of BCAAs on that.

Preclinical characterization of a (S)-N-(4-cyano-3-trifluoromethyl-phenyl)-3-(3-fluoro, 4-chlorophenoxy)-2-hydroxy-2-methyl-propanamide: a selective androgen receptor modulator for hormonal male contraception.


The pharmacologic effects of (S)-N-(4-cyano-3-trifluoromethyl-phenyl)-3-(3-fluoro, 4-chlorophenoxy)-2-hydroxy-2-methyl-propanamide (S-23) were characterized in male rats as an animal model of hormonal male contraception. S-23 showed high binding affinity (inhibitory constant = 1.7 +/- 0.2 nm) and was identified as a full agonist in vitro. In castrated male rats, the ED50 of S-23 in the prostate and levator ani muscle was 0.43 and 0.079 mg/d, respectively. In intact male rats treated for 14 d, S-23 alone suppressed LH levels by greater than 50% at doses greater than 0.1 mg/d, with corresponding decreases in the size of the prostate but increases in the size of levator ani muscle. In intact male rats treated for up to 10 wk with S-23 and estradiol benzoate (EB; necessary to maintain sexual behavior in rats), S-23 showed biphasic effects on androgenic tissues and spermatogenesis by suppressing serum concentrations of LH and FSH. EB alone showed no effect on spermatogenesis. In the EB + S-23 (0.1 mg/d) group, four of six animals showed no sperm in the testis and zero pregnancies (none of six) in mating trials. After termination of treatment, infertility was fully reversible, with a 100% pregnancy rate observed after 100 d of recovery. S-23 increased bone mineral density and lean mass but reduced fat mass in a dose-dependent manner. This is the first study to show that a selective androgen receptor modulator combined with EB is an effective and reversible regimen for hormonal male contraception in rats. The beneficial effects of S-23 on the muscle, tissue selectivity, and favorable pharmacokinetic properties make it a strong candidate for use in oral male contraception.

PMID: 18772237 [PubMed – indexed for MEDLINE] PMCID: PMC2630904

Source: http://www.ncbi.nlm.nih.gov/pubmed/18772237

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