How Long Does S23 Stay in Your System? What the Published Literature Reports

The question "how long does S23 stay in your system" usually bundles four different questions: what the half-life is, when the compound is fully cleared, how long analytical testing can still find traces, and what changes those numbers from one person to the next. For S23, the honest answer is that the published record answers only part of this. There is no human clinical pharmacokinetic trial among the peer-reviewed studies cited on this page that reports an S23 half-life, volume of distribution or clearance rate in people. What does exist is anti-doping analytical chemistry, which measures something related but distinct: how long urinary metabolites remain detectable after defined exposures.

This page is for educational purposes only and is not medical advice; consult a licensed physician with any questions about a medical condition, a medication, or a research compound. Nothing here describes how to use S23, and no dosing, timing or protocol information is provided.

What S23 Is — and Why Peptide Pharmacokinetics Do Not Apply

S-23 is a nonsteroidal selective androgen receptor modulator (SARM), a small synthetic molecule rather than a peptide. A preclinical characterization published in Endocrinology described (S)-N-(4-cyano-3-trifluoromethyl-phenyl)-3-(3-fluoro, 4-chlorophenoxy)-2-hydroxy-2-methyl-propanamide as a selective androgen receptor modulator investigated as a candidate for hormonal male contraception (PMID 18772237).

That distinction matters for any clearance discussion. Peptides are typically cleared by peptidase degradation and renal filtration, which is why many research peptides show half-lives measured in minutes. Small nonsteroidal molecules such as SARMs are generally handled by hepatic phase I and phase II metabolism — oxidation, hydroxylation, then conjugation — and excreted largely in urine as metabolites. Those are general pharmacology principles, not S23-specific measurements, and they are flagged as such throughout this page. Anyone extrapolating a peptide half-life rule onto S23 is applying the wrong model to the wrong chemistry.

Is There a Published Human Half-Life for S23?

Not in the literature cited here. The verified studies on this page are preclinical characterization work (PMID 18772237) and doping-control analytical studies focused on urinary elimination profiles (PMID 40277337). None of them is a clinical pharmacokinetic trial in healthy volunteers with sampled plasma concentration-time curves, which is the study design that would yield a published human half-life.

This is a common situation for compounds that never completed regulated clinical development. S23 is not an approved medicine in the United States, the European Union or elsewhere; it is sold and handled as a research chemical, and SARMs as a class are not approved for human therapeutic use. Where a compound skips formal Phase I pharmacokinetics, the numbers circulating online — "half-life of X hours" — usually trace back to vendor copy or forum consensus rather than to an indexed study. Readers comparing figures should check whether a stated half-life is attached to a citation at all.

What Doping-Control Studies Actually Measured

Oral exposure and contamination scenarios

The most directly relevant published work on S23 elimination is an investigation of the urinary metabolite elimination profile of the selective androgen receptor modulator S-23 in studies designed to mimic ingestion of a contaminated product, conducted for doping-control purposes (PMID 40277337). The research question there was not therapeutic pharmacokinetics; researchers examined what appears in urine, in what metabolic form, and over what elimination course, after exposures consistent with trace contamination rather than deliberate administration.

That framing is important for interpreting detectability. Contamination-scenario studies exist because athletes have tested positive after consuming supplements containing undeclared SARMs, and anti-doping laboratories needed to know whether a low-level exposure can still produce a reportable finding — and for how long (PMID 40277337). The practical implication reported in that line of work is that detectability can persist beyond the point at which a parent compound would be pharmacologically meaningful, because modern mass spectrometry targets metabolites at very low concentrations.

Transdermal exposure

A separate 2025 analytical study explored transdermal SARM exposure, analysing elimination profiles and metabolism for doping-control purposes (PMID 40632609). Route of exposure changes the shape of an elimination curve: absorption through skin is slower and more prolonged than gastrointestinal absorption, which can flatten peak concentrations while extending the tail of detectable metabolites. The study examined that question specifically in the SARM class rather than assuming oral data would transfer (PMID 40632609).

Half-Life, Clearance and Detection Window Are Three Different Clocks

These terms get used interchangeably and should not be.

• Half-life is the time for plasma concentration to fall by half. It is a pharmacokinetic parameter derived from blood sampling. For S23 in humans, the cited literature does not report one.
• Functional clearance is conventionally estimated at roughly four to five half-lives, at which point about 94–97% of a dose has been eliminated. That is a general pharmacokinetic convention, not an S23 finding, and it cannot be calculated without a half-life to start from.
• Detection window is how long an analytical method can still identify the compound or its metabolites in a biological matrix. It depends on assay sensitivity, the matrix sampled, the metabolite targeted, and the exposure itself — which is exactly why the S-23 urinary metabolite work was framed around specific ingestion scenarios (PMID 40277337).

Detection windows routinely outlast pharmacological activity. A compound can be biologically irrelevant and still analytically reportable.

Drug Testing: What Is and Is Not Screened For

Stated plainly, because this is where most confusion sits:

Anti-doping laboratories do not look for the parent compound alone. The S-23 elimination work characterized urinary metabolites precisely because metabolite markers extend and clarify what a laboratory can report (PMID 40277337), and the transdermal study applied the same metabolite-profiling logic to a different exposure route (PMID 40632609).

Factors That Change Clearance

The following are general pharmacokinetic determinants described across drug metabolism science. They are not S23-specific measurements, and no cited study quantified them for this compound.

1. Route of exposure. Oral, transdermal and other routes produce different absorption kinetics; the transdermal SARM study was designed around exactly that variable (PMID 40632609).
2. Total exposure and duration. Larger cumulative exposure generally lengthens the tail of low-concentration metabolites available to a sensitive assay — the reason contamination-level and administration-level scenarios are studied separately (PMID 40277337).
3. Hepatic function and enzyme variability. Phase I oxidation and phase II conjugation capacity differ between individuals through genetics, age, liver health and co-administered substances.
4. Renal function and urine characteristics. Urinary excretion rate, hydration status and specific gravity influence measured concentrations, which is why anti-doping laboratories apply dilution criteria.
5. Body composition and distribution. Lipophilic small molecules distribute into tissue compartments and redistribute slowly, extending terminal elimination.
6. Assay sensitivity. The single most underappreciated variable: as instrumentation improves, the same biology yields a longer detection window with no change in the compound itself.

Adverse Events and Biological Effects: What Studies Report

Clearance cannot be separated from what the compound does while present. The preclinical characterization in Endocrinology evaluated S-23 as a selective androgen receptor modulator for hormonal male contraception (PMID 18772237) — an application that, by definition, rests on the compound's ability to alter reproductive endocrine signalling in the models studied. No human safety trial for S23 appears in the verified literature used here, so no human adverse-event frequencies, no organ-toxicity rates and no reversibility timelines can be reported from these sources. Statements online that describe such outcomes in humans are not supported by the studies cited on this page.

The doping-control literature likewise addressed analysis rather than safety: those studies reported metabolite identification and elimination behaviour for detection purposes (PMID 40277337, PMID 40632609) and did not set out to characterize clinical toxicity.

What the Evidence Supports — and What It Does Not

Related Reading

• S23: what the research literature covers
• How long do peptides stay in your system?

References

• 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 (Biomedical Chromatography, 2025)
• Exploring transdermal SARMs exposure: analysis of the elimination profiles and metabolism for doping control purposes (Journal of Analytical Toxicology, 2025)
• 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)