{"title":"S-23","description":"\u003cp\u003eS-23, also written S23 and known chemically as (S)-N-(4-cyano-3-trifluoromethyl-phenyl)-3-(3-fluoro-4-chlorophenoxy)-2-hydroxy-2-methyl-propanamide, is a non-steroidal selective androgen receptor modulator (SARM) of the aryl-propionamide family developed by GTx. It was investigated in rats as a candidate for reversible hormonal male contraception rather than for muscle wasting. This page lists every brand of S-23 stocked at Free Muscle, compared on strength per capsule, capsules per pack and batch testing, and summarises the published research and its limits.\u003c\/p\u003e\n\u003ch2\u003eWhat is S-23?\u003c\/h2\u003e\n\u003cp\u003eS-23 is a close structural relative of ostarine and andarine, sharing their aryl-propionamide backbone but carrying a chloro- and fluoro-substituted phenoxy ring. In the original characterisation it bound the androgen receptor (AR) with an inhibitory constant of about 1.7 nanomolar and behaved as a full agonist in vitro, which distinguishes it from partial agonists such as andarine. In castrated rats it was markedly more potent in the levator ani muscle than in the prostate, the pattern that defines a SARM.\u003c\/p\u003e\n\u003cp\u003eWhat sets S-23 apart is the reason it was studied. Because a full AR agonist strongly suppresses luteinising hormone and follicle-stimulating hormone from the pituitary, and therefore suppresses sperm production, GTx explored S-23 combined with an oestrogen as a reversible male contraceptive in rats. The compound never entered published human trials for any indication. S-23 has never been approved as a medicine by the MHRA, EMA, FDA or any other regulator, and its development appears to have stopped at the preclinical stage.\u003c\/p\u003e\n\u003ch2\u003eWhat the published research reports\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003ePreclinical characterisation for male contraception (2009).\u003c\/strong\u003e Jones and colleagues characterised S-23 in male rats. In castrated animals the ED50 in the levator ani muscle was roughly five times lower than in the prostate, a separation in favour of muscle. In intact rats treated for two weeks, S-23 alone suppressed LH by more than 50 per cent, with a corresponding decrease in prostate size and increase in levator ani size. In a ten-week study combining S-23 with oestradiol benzoate, four of six animals in one group had no sperm in the testis and none of six produced pregnancies in mating trials; fertility was fully restored after 100 days off treatment. S-23 also increased bone mineral density and lean mass and reduced fat mass dose-dependently. These are rat data only.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eReview of SARM discovery (2005).\u003c\/strong\u003e Chen, Kim and Dalton reviewed the aryl-propionamide programme that produced S-4, S-22 (later ostarine) and related compounds, describing the structure-activity relationships that convert an anti-androgen scaffold into a tissue-selective agonist and the therapeutic rationale for pursuing muscle, bone and pituitary effects with reduced prostate stimulation.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eUK market analysis of SARM products (2021).\u003c\/strong\u003e Leaney and colleagues, working in a UK laboratory, analysed supplement products marketed as SARMs to UK consumers by high-resolution mass spectrometry. They found products with no active ingredient, products containing undeclared prohibited substances, and measured concentrations that frequently disagreed with the label. They also noted that toxicity data for SARMs, particularly in combination, are incomplete.\u003c\/p\u003e\n\u003cp\u003eAll efficacy findings above come from rats or from review of preclinical work. There are no published human trials of S-23, and none of these findings is a claim about the products listed on this page.\u003c\/p\u003e\n\u003ch2\u003eBrands of S-23 we stock\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eiMuscle S-23, 15mg, 60 capsules.\u003c\/strong\u003e Capsule form, 900mg of compound per pack. A certificate of analysis is shown on the listing only where iMuscle has supplied one for the batch we hold; if none is displayed, none is available for that batch. \u003ca href=\"\/products\/imuscle-s-23-60-15mg\"\u003eView the iMuscle S-23 listing\u003c\/a\u003e.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eFree Muscle does not currently produce its own S-23, so there is no Janoshik-assayed Free Muscle batch on this page at present. Any Free Muscle-brand line added later will carry batch-level Janoshik testing like the rest of our range.\u003c\/p\u003e\n\u003ch3\u003eHow to compare them\u003c\/h3\u003e\n\u003cp\u003eMultiply strength per capsule by capsules per pack to get total milligrams (15mg by 60 gives 900mg). Divide the pack price by that figure for cost per milligram so that a 15mg pack can be compared fairly against a 10mg or 25mg one from another supplier. Then weigh the certificate. S-23 is a less common compound than ostarine or LGD-4033, so an independent identity assay against a verified reference standard is the only objective evidence of what a capsule contains. Our guide to \u003ca href=\"\/blogs\/news\/price-per-mg-compare-sarms-peptides\"\u003eprice per milligram\u003c\/a\u003e covers the arithmetic.\u003c\/p\u003e\n\u003ch2\u003eBatch testing and certificates of analysis\u003c\/h2\u003e\n\u003cp\u003eA certificate of analysis (COA) answers the two questions that matter about an S-23 capsule: is the compound what the label says, and how much is present. A genuine batch certificate is issued by an independent laboratory, names the lot number, and reports identity (by HPLC or mass spectrometry against a reference standard) and assayed purity or content.\u003c\/p\u003e\n\u003cp\u003eEvery Free Muscle-brand batch is assayed by Janoshik Analytical, an independent laboratory, and the certificate for the batch you receive is sent on request by email. For other brands we show a COA only where the manufacturer has supplied one for the batch we hold. A generic PDF with no batch number, or one dated long before the product was made, is not a batch certificate and tells you nothing about the capsules in your hand. Our \u003ca href=\"\/pages\/lab-tests\"\u003elab tests page\u003c\/a\u003e explains how to read a Janoshik certificate and match it to your batch.\u003c\/p\u003e\n\u003ch2\u003eLegal status in the UK\u003c\/h2\u003e\n\u003cp\u003eS-23 is not a licensed medicine in the United Kingdom. It has never been granted a marketing authorisation by the MHRA, and it is not an authorised food supplement or a permitted novel food ingredient. It cannot legally be sold or labelled for human consumption. Free Muscle sells S-23 to adults aged 18 or over for laboratory and research purposes only, and every listing states this. S-23 falls within section S1.2 of the World Anti-Doping Agency Prohibited List (Other Anabolic Agents), which covers all SARMs, and is prohibited at all times. Anyone subject to anti-doping rules should treat any product in this class as prohibited at all times, in and out of competition. For a fuller overview of the class, see our \u003ca href=\"\/blogs\/news\/what-are-sarms-the-2026-research-guide\"\u003eresearch guide to SARMs\u003c\/a\u003e.\u003c\/p\u003e\n\u003ch2\u003eStorage and handling\u003c\/h2\u003e\n\u003cp\u003eKeep S-23 capsules in the original sealed container in a cool, dry place away from light and heat. Do not decant into unlabelled containers, and record the batch number so that a COA request can be matched to the exact material. Keep out of reach of children and pets, and follow standard laboratory good practice: gloves when handling, no eating or drinking in the work area, and disposal in line with local rules for research chemicals.\u003c\/p\u003e\n\u003ch2\u003eDelivery and returns\u003c\/h2\u003e\n\u003cp\u003eFree Muscle (FreeMuscle LTD, Scunthorpe) is a UK company. Every order is sent with free tracked UK delivery in plain packaging, and orders placed before 2pm on a weekday are processed the same working day. EU delivery is 3 to 7 working days. Unopened items can be returned within 30 days, and customers must be 18 or over. Read the \u003ca href=\"\/pages\/shipping\"\u003eshipping page\u003c\/a\u003e and \u003ca href=\"\/pages\/guarantee\"\u003eguarantee page\u003c\/a\u003e for full terms.\u003c\/p\u003e\n\u003ch2\u003eRelated reading\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\u003ca href=\"\/blogs\/news\/what-are-sarms-the-2026-research-guide\"\u003eWhat are SARMs? The 2026 research guide\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/blogs\/news\/sarms-explained-how-selective-androgen-receptor-modulators-work-1135-86\"\u003eSARMs explained: how selective androgen receptor modulators work\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/blogs\/news\/how-to-read-a-certificate-of-analysis\"\u003eHow to read a certificate of analysis\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/blogs\/news\/what-is-janoshik-analytical\"\u003eWhat is Janoshik Analytical?\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eRelated collections: \u003ca href=\"\/collections\/andarine\"\u003eAndarine (S-4)\u003c\/a\u003e, \u003ca href=\"\/collections\/ostarine\"\u003eOstarine (MK-2866)\u003c\/a\u003e, \u003ca href=\"\/collections\/brand-imuscle\"\u003eiMuscle\u003c\/a\u003e, \u003ca href=\"\/collections\/sarms\"\u003eall SARMs\u003c\/a\u003e.\u003c\/p\u003e\n\u003cp\u003e\u003cem\u003eS-23 is sold strictly for laboratory research use only. It is not a licensed medicine, has not been evaluated or approved by the MHRA, EMA or FDA, is not a food supplement and is not for human consumption. Buyers must be 18 or over. Nothing on this page is medical advice, dosing advice or a recommendation to use this compound in any way; the published findings summarised above describe study participants and laboratory models, not the products listed.\u003c\/em\u003e\u003c\/p\u003e","products":[{"product_id":"imuscle-s-23-60-15mg","title":"iMuscle S-23 — 60 caps, 15mg","description":"\u003cp\u003eiMuscle S-23 is a pack of 60 capsules stated at 15 mg each, 900 mg of S-23 in total. S-23 is a potent non-steroidal selective androgen receptor modulator that was studied in rats as a candidate for hormonal male contraception. It has never been tested in a published clinical trial; the only human data come from anti-doping excretion studies. Free Muscle stocks this iMuscle product through Muscle Market for laboratory research by adults aged 18 and over.\u003c\/p\u003e\u003ch2\u003eAbout S-23\u003c\/h2\u003e\u003cp\u003eS-23 is a non-steroidal selective androgen receptor modulator from the same aryl-propionamide family as andarine and ostarine. It was investigated not for muscle wasting but as a candidate for hormonal male contraception, because of how effectively it suppressed the pituitary-gonadal axis in animals.\u003c\/p\u003e\u003cp\u003eThe key paper is a 2009 preclinical characterisation in rats (Jones et al., 2009). S-23 bound the androgen receptor with an inhibitory constant of about 1.7 nanomolar and behaved as a full agonist in cell assays. In the animals it increased levator ani muscle weight and, when combined with an oestrogen, suppressed spermatogenesis and produced infertility that reversed once treatment stopped. The same work recorded a strong decrease in luteinising hormone and follicle-stimulating hormone. In castrated rats it acted on the prostate as well as on muscle, though at higher amounts, while in intact rats prostate size fell as luteinising hormone was suppressed. No clinical trial of S-23 has been published, and no clinical development has been reported. Its suppressive effect on the animals' own reproductive hormones is therefore its best-documented property. These rodent findings are not claims about this listing.\u003c\/p\u003e\u003ch3\u003eName and chemical identity\u003c\/h3\u003e\u003cp\u003eS-23 never reached clinical development, so it is known only by its series code, also written S23, and is easily confused with S-22 (an early code for ostarine) and S-4 (andarine). A certificate for this pack should match these PubChem identifiers:\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eSystematic name\u003c\/strong\u003e: (2S)-3-(4-chloro-3-fluorophenoxy)-N-[4-cyano-3-(trifluoromethyl)phenyl]-2-hydroxy-2-methylpropanamide\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCAS number\u003c\/strong\u003e: 1010396-29-8\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFormula and molecular weight\u003c\/strong\u003e: C18H13ClF4N2O3, 416.8 g\/mol\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInChIKey\u003c\/strong\u003e: SSFVOEAXHZGTRJ-KRWDZBQOSA-N\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePubChem CID\u003c\/strong\u003e: 24892822\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eThis listing\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eCompound: S-23\u003c\/li\u003e\n\u003cli\u003eBrand: iMuscle\u003c\/li\u003e\n\u003cli\u003eForm: capsules\u003c\/li\u003e\n\u003cli\u003ePack size: 60 capsules\u003c\/li\u003e\n\u003cli\u003eStated strength: 15 mg per capsule (manufacturer's label claim)\u003c\/li\u003e\n\u003cli\u003eStated total per pack: 900 mg\u003c\/li\u003e\n\u003cli\u003eIntended use: laboratory research only, not for human consumption\u003c\/li\u003e\n\u003cli\u003eSold to adults aged 18 and over\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eThe strength is the manufacturer's label claim; only a batch certificate confirms it. To compare brands of S-23, use total milligrams per pack, as explained in \u003ca href=\"\/blogs\/news\/price-per-mg-compare-sarms-peptides\"\u003eprice per milligram\u003c\/a\u003e.\u003c\/p\u003e\u003ch2\u003eS-23 in the UK: buying, legal status and what to check\u003c\/h2\u003e\u003cp\u003eSearches such as \"S23 SARM UK\" and \"S-23 SARM for sale\" ask two things: whether S-23 can be bought lawfully in Britain, and how to tell a listing that can be checked from one that must be taken on trust.\u003c\/p\u003e\u003ch3\u003eThe legal position\u003c\/h3\u003e\u003cp\u003eS-23 is not a licensed medicine in the UK: it has no MHRA marketing authorisation, and no regulator anywhere has granted one. Nor is it an authorised food supplement, so it cannot lawfully be sold for human consumption, although it is not a controlled substance. Free Muscle supplies it to adults aged 18 or over for laboratory research only. WADA prohibits it at all times under section S1 (anabolic agents) of its Prohibited List. Buyers are responsible for the rules that bind them, including any anti-doping code and, for EU orders, local import rules. The wider class is covered in \u003ca href=\"\/blogs\/news\/what-are-sarms-the-2026-research-guide\"\u003eWhat are SARMs? The 2026 research guide\u003c\/a\u003e.\u003c\/p\u003e\u003ch3\u003eWhat a listing should show, and what this one shows\u003c\/h3\u003e\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eCheck\u003c\/th\u003e\n\u003cth\u003eWhy it matters for S-23\u003c\/th\u003e\n\u003cth\u003eThis listing\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eCompound named precisely\u003c\/td\u003e\n\u003ctd\u003eA certificate can only be matched to an exact name\u003c\/td\u003e\n\u003ctd\u003eS-23, with the identifiers above\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eStrength and capsule count\u003c\/td\u003e\n\u003ctd\u003eNeeded for a pack total and a price per milligram\u003c\/td\u003e\n\u003ctd\u003e15 mg by 60 capsules, 900 mg per pack (label claim)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCertificate for the batch sold\u003c\/td\u003e\n\u003ctd\u003eThe only evidence of what the capsules contain\u003c\/td\u003e\n\u003ctd\u003eShown only where iMuscle supplies one for the batch we hold; otherwise we say none exists\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eA named seller\u003c\/td\u003e\n\u003ctd\u003eSomeone accountable for the sale\u003c\/td\u003e\n\u003ctd\u003eFreeMuscle LTD, a UK company based in Scunthorpe\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eResearch-only terms\u003c\/td\u003e\n\u003ctd\u003eDirections or promised results signal a sale for consumption\u003c\/td\u003e\n\u003ctd\u003eLaboratory research, adults 18+, no directions or outcome claims\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDelivery and returns\u003c\/td\u003e\n\u003ctd\u003eShows who holds the parcel, and on what terms\u003c\/td\u003e\n\u003ctd\u003eFree tracked UK delivery on every order, in plain packaging; same-day processing for orders before 2pm Monday to Friday; EU delivery in 3-7 working days; unopened items returnable within 30 days\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\u003cp\u003eA label alone proves little. Anti-doping researchers in Cologne name contaminated dietary supplements as one route by which SARMs have reached athletes' samples (Alhalabi et al., 2025): a tub can carry a substance it does not declare. Reviews of \"S23\" record what writers felt, not what they took. Full terms are on our \u003ca href=\"\/pages\/shipping\"\u003edelivery\u003c\/a\u003e and \u003ca href=\"\/pages\/guarantee\"\u003eguarantee\u003c\/a\u003e pages, and further checks are in \u003ca href=\"\/blogs\/news\/how-to-choose-a-sarms-supplier-uk-checklist\"\u003ehow to choose a SARMs supplier in the UK\u003c\/a\u003e.\u003c\/p\u003e\u003ch2\u003eCapsules compared with other forms\u003c\/h2\u003e\u003cp\u003eBesides capsules, S-23 circulates as tablets and as liquids labelled in milligrams per millilitre. The molecule does not change between them; what changes is where the stated amount is fixed and what a certificate can confirm. No published study has compared formats of S-23.\u003c\/p\u003e\u003cp\u003eIn a capsule or tablet the amount per unit is fixed at the factory, so a laboratory can report milligrams per capsule, the figure that tests the 15 mg claim here, although a pooled assay gives only the average and unit-to-unit variation shows only when capsules are tested singly. A liquid's certificate reports concentration on the test date, and the amount in any portion then depends on how accurately a volume is drawn, whether the compound stays dissolved in the cold, and solvent lost from a bottle opened many times.\u003c\/p\u003e\u003cp\u003eAs a small synthetic molecule rather than a peptide, S-23 is not open in the same way to the objection that digestive enzymes break swallowed peptides apart (see \u003ca href=\"\/blogs\/news\/do-oral-peptides-work\"\u003edo oral peptides work\u003c\/a\u003e). The oral excretion studies described under detection below gave it by mouth, one as a tablet, and we know of no published study of it by injection. A dry powder in a shell is also kept from the water and solvents in which breakdown usually runs fastest, though that is general chemistry, not a measured result for S-23.\u003c\/p\u003e\u003ch2\u003eS-23 compared with RAD-140\u003c\/h2\u003e\u003cp\u003e\"S23 vs RAD140\" is the comparison searched most often for this compound, usually as a question about which is stronger. Chemistry and regulation answer part of it; the rest has never been studied.\u003c\/p\u003e\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eFeature\u003c\/th\u003e\n\u003cth\u003eS-23 (this product)\u003c\/th\u003e\n\u003cth\u003eRAD-140\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eChemical family\u003c\/td\u003e\n\u003ctd\u003eAryl-propionamide, like andarine and ostarine\u003c\/td\u003e\n\u003ctd\u003eA different scaffold built around a 1,3,4-oxadiazole ring\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFormula, molecular weight, CAS\u003c\/td\u003e\n\u003ctd\u003eC18H13ClF4N2O3, 416.8, 1010396-29-8\u003c\/td\u003e\n\u003ctd\u003eC20H16ClN5O2, 393.8, 1182367-47-0\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePurpose of the research\u003c\/td\u003e\n\u003ctd\u003eHormonal male contraception, in rats (2009)\u003c\/td\u003e\n\u003ctd\u003eAnabolic androgen action in preclinical models (Radius Health, 2011); later breast cancer\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eStudies in people\u003c\/td\u003e\n\u003ctd\u003eNo clinical trial; anti-doping excretion studies only\u003c\/td\u003e\n\u003ctd\u003eOne Phase 1 trial in 22 women with advanced breast cancer; anti-doping excretion studies\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBest-documented effects\u003c\/td\u003e\n\u003ctd\u003eStrong LH and FSH suppression; with an oestrogen, reversible loss of sperm production (rats)\u003c\/td\u003e\n\u003ctd\u003eRaised AST, ALT and bilirubin, the most frequent adverse events in that trial (LoRusso et al., 2022)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eLicensed as a medicine\u003c\/td\u003e\n\u003ctd\u003eNowhere\u003c\/td\u003e\n\u003ctd\u003eNowhere\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWADA\u003c\/td\u003e\n\u003ctd\u003eS1.2, prohibited as a SARM\u003c\/td\u003e\n\u003ctd\u003eS1.2, named among the examples\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\u003cp\u003eS-23's reputation for strength rests on the 2009 cell work, where it bound the receptor tightly and switched it on fully; Radius Health likewise called RAD-140 potent. Those results come from different laboratories, assays and species, and no study has tested the two side by side, so no ranking is supported. Receptor potency would in any case say nothing about effects or risks in a person.\u003c\/p\u003e\u003cp\u003eThe evidence is unequal: RAD-140 has adverse events and blood levels recorded in supervised patients, while S-23 has rat pharmacology and urine data from anti-doping volunteers. No equivalence between their milligram labels has been established, and both are sold here for laboratory research only. RAD-140 brands, including \u003ca href=\"\/products\/imuscle-testolon-rad-140-60-10mg\"\u003eiMuscle Testolone RAD-140\u003c\/a\u003e, are compared in the \u003ca href=\"\/collections\/rad-140\"\u003eRAD-140 (Testolone) collection\u003c\/a\u003e, and its research record is set out in \u003ca href=\"\/blogs\/news\/rad-140-testolone-what-the-research-says\"\u003eRAD-140 (testolone): what the research says\u003c\/a\u003e.\u003c\/p\u003e\u003ch2\u003eReading the certificate of analysis for this product\u003c\/h2\u003e\u003cp\u003eiMuscle is a third-party brand, so any certificate of analysis (COA) is the manufacturer's, not ours. Where iMuscle has supplied one for the batch we hold, we show it; where none exists, we say so rather than show a generic document. Our Janoshik Analytical batch testing covers Free Muscle-brand compounds only, not iMuscle. At a minimum, a real batch certificate carries the lot number printed on the pack, the test method (HPLC or LC-MS) and a purity figure; a full S-23 certificate lets you check each of these:\u003c\/p\u003e\u003col\u003e\n\u003cli\u003e\n\u003cstrong\u003eThe right compound.\u003c\/strong\u003e S-23 by name, ideally with CAS 1010396-29-8. A report for S-22, S-4 or an unnamed \"SARM\" does not describe this pot.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIdentity, with the method stated.\u003c\/strong\u003e HPLC matches a peak to an S-23 reference standard; LC-MS adds a mass that should fit C18H13ClF4N2O3 (416.8 g\/mol). With one chlorine atom, S-23 should also give a companion signal two mass units higher, roughly a third the height of the main one.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePurity.\u003c\/strong\u003e The percentage of chromatogram peak area that is S-23. A high figure says the material is clean, not that each capsule holds 15 mg.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eContent per capsule.\u003c\/strong\u003e A measured milligram figure to set against the 15 mg label claim; sixty times it is the real pack total.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWhich mirror-image form.\u003c\/strong\u003e S-23 is the (2S) form. Its mirror image has the same formula and mass, which ordinary HPLC and LC-MS cannot tell apart; unless a chiral method is named, this has not been checked.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLot number, test date and laboratory.\u003c\/strong\u003e The lot must match your pot; the date shows the result's age; a named laboratory can confirm it issued the report.\u003c\/li\u003e\n\u003c\/ol\u003e\u003cp\u003eIf an iMuscle document falls short on any of these, \u003ca href=\"\/pages\/contact\"\u003econtact us\u003c\/a\u003e with your lot number and we will tell you what exists for the stock we hold. See also \u003ca href=\"\/blogs\/news\/how-to-read-a-certificate-of-analysis\"\u003ehow to read a COA\u003c\/a\u003e and our \u003ca href=\"\/pages\/lab-tests\"\u003elab tests\u003c\/a\u003e page.\u003c\/p\u003e\u003ch2\u003eDetection, sport and testing\u003c\/h2\u003e\u003cp\u003eS-23 falls under section S1.2 (other anabolic agents) of the WADA Prohibited List, which covers SARMs as a class, and is banned in and out of competition. It lay behind five adverse analytical findings reported in 2022 (Alhalabi et al., 2025), and under strict liability an athlete answers for any prohibited substance in their sample, however it got there.\u003c\/p\u003e\u003cp\u003eOral excretion studies give detection times. At the Institute of Legal Medicine in Strasbourg, a single volunteer took one oral amount in the milligram range; unchanged S-23 was found in hydrolysed urine from 2 hours to 28 days afterwards, as was a hydroxylated metabolite (Ameline et al., 2022). At the German Sport University Cologne, volunteers took single and repeated amounts of 1, 10 or 50 micrograms, the scale of a contaminated product. With a method able to detect 1 picogram per millilitre, a single microgram was traced for an average of up to 253 hours, about ten days, and a single 50 micrograms for up to 544 hours, about 23 days; 18 metabolites were identified (Alhalabi et al., 2025).\u003c\/p\u003e\u003cp\u003eThose figures come from one person and from small groups given very small amounts. Detection after repeated or larger milligram quantities has not been studied, so for this product: detectable, window not established. Anyone subject to anti-doping rules should treat any contact with S-23 as a risk of an adverse finding.\u003c\/p\u003e\u003ch2\u003eStorage, stability and handling\u003c\/h2\u003e\u003cp\u003eWe know of no published stability study of S-23 in any form, so iMuscle's printed expiry or best-before date is the working limit, and a certificate describes the batch on its test date, not on the day the pot is opened.\u003c\/p\u003e\u003cp\u003eKeep the capsules in their original pot with the lid closed, because its lot number links them to any certificate. Store it cool, dry and dark, in a cupboard rather than a kitchen, bathroom or windowsill; humidity softens shells and makes powder cake. Let a cold pot reach room temperature before opening it so condensation does not form inside. Shells that have darkened, gone soft or fused together suggest the contents have changed since the batch was tested; keep that pot apart and \u003ca href=\"\/pages\/contact\"\u003etell us\u003c\/a\u003e its lot number.\u003c\/p\u003e\u003cp\u003eWear gloves whenever a capsule is opened or powder is spilled, and work away from food and drink. Label anything taken out of the pot with compound, lot and date. Store the pot where children and pets cannot reach it, and treat unwanted material as chemical waste under local rules rather than tipping it into a household bin or drain. Unopened items can be returned within 30 days, so a pot left sealed keeps that option open.\u003c\/p\u003e\u003ch2\u003eGlossary\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eAryl-propionamide\u003c\/strong\u003e: the structural series of S-23, ostarine (S-22) and andarine (S-4), source of the S-numbered codes.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFull agonist\u003c\/strong\u003e: a compound that activates a receptor as completely as the body's own hormone, as S-23 did in 2009 cell assays; some related SARMs are only partial agonists.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInhibitory constant (Ki)\u003c\/strong\u003e: how tightly a compound binds a receptor in a competition assay; lower means tighter, about 1.7 nanomolar for S-23.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLevator ani\u003c\/strong\u003e: a small androgen-sensitive pelvic muscle weighed in rat studies as a marker of anabolic activity.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLH and FSH\u003c\/strong\u003e: luteinising hormone and follicle-stimulating hormone, released by the pituitary gland to drive testosterone and sperm production in the testes.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSpermatogenesis\u003c\/strong\u003e: sperm production in the testes.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eReference standard\u003c\/strong\u003e: material of certified identity used as the benchmark for identifying and measuring a sample.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHydrolysed urine\u003c\/strong\u003e: urine treated with an enzyme that strips attached groups such as glucuronic acid, freeing a compound and its metabolites for measurement.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAdverse analytical finding\u003c\/strong\u003e: a laboratory's formal report that a prohibited substance or its metabolite is present in an athlete's sample.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStrict liability\u003c\/strong\u003e: the anti-doping rule that athletes answer for whatever is found in their sample, whatever its source.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eRelated\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003e\n\u003ca href=\"\/collections\/s-23\"\u003eAll brands of S-23\u003c\/a\u003e, compared on strength, pack size and batch testing\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"\/collections\/brand-imuscle\"\u003eAll iMuscle products\u003c\/a\u003e stocked at Free Muscle\u003c\/li\u003e\n\u003cli\u003eRelated SARMs: \u003ca href=\"\/collections\/rad-140\"\u003eRAD-140 (Testolone)\u003c\/a\u003e, \u003ca href=\"\/collections\/andarine\"\u003eAndarine (S-4)\u003c\/a\u003e, \u003ca href=\"\/collections\/ostarine\"\u003eOstarine (MK-2866)\u003c\/a\u003e and \u003ca href=\"\/collections\/sarms\"\u003eall SARMs\u003c\/a\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"\/pages\/shipping\"\u003eDelivery\u003c\/a\u003e and \u003ca href=\"\/pages\/guarantee\"\u003ereturns\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e\u003cem\u003eThis product is supplied for laboratory research use only. It is not a medicine, has not been evaluated by the MHRA, EMA or FDA, and is not for human consumption. Sold to adults aged 18 and over. Nothing on this page is medical, dosing or usage advice.\u003c\/em\u003e\u003c\/p\u003e\u003ch2\u003eReferences\u003c\/h2\u003e\u003col\u003e\n\u003cli\u003eJones A, et al. 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. Endocrinology. 2009;150(1):385-95. PMID: 18772237.\u003c\/li\u003e\n\u003cli\u003eAmeline A, et al. In vitro characterization of S-23 metabolites produced by human liver microsomes, and subsequent application to urine after a controlled oral administration. J Pharm Biomed Anal. 2022;212:114660. PMID: 35182830.\u003c\/li\u003e\n\u003cli\u003eAlhalabi H, et al. Investigations Into the Urinary Metabolite Elimination Profile of the Selective Androgen Receptor Modulator S-23 in Studies Mimicking Contaminated Product Ingestion for Doping Control Purposes. Biomed Chromatogr. 2025;39(6):e70090. PMID: 40277337.\u003c\/li\u003e\n\u003cli\u003eLoRusso P, et al. A First-in-Human Phase 1 Study of a Novel Selective Androgen Receptor Modulator (SARM), RAD140, in ER+\/HER2- Metastatic Breast Cancer. Clin Breast Cancer. 2022;22(1):67-77. PMID: 34565686.\u003c\/li\u003e\n\u003c\/ol\u003e","brand":"iMuscle","offers":[{"title":"Default Title","offer_id":48468980138210,"sku":null,"price":58.99,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0772\/3499\/5426\/files\/S-23_800x_0f998b39-6402-4c4a-9f31-a7dfe2de1826.jpg?v=1789931414"}],"url":"https:\/\/freemuscle.co.uk\/collections\/s-23.oembed","provider":"Free Muscle","version":"1.0","type":"link"}