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Background And Regulatory Status — Worked Examples

By Editorial Desk · published 2026-03-23 · last reviewed 2026-04-09 · News

regulatory status is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.

Last reviewed on 2026-04-09. Where a claim depends on a specific study, the study is described rather than over-claimed.

Background and Regulatory Status

Legal status varies by country. In some places, cardarine is controlled under medicines or psychoactive substances laws; in others, it may be sold with minimal oversight as a research chemical. Customs agencies have intercepted shipments, and several national health agencies have issued warnings about products marketed for bodybuilding or performance enhancement. The lack of a standardized pharmaceutical supply means identity, purity, and contamination levels can differ widely between samples. These factors make cardarine a regulatory and public health concern rather than a conventional prescription drug.

Cardarine is a common name for GW501516, a synthetic compound first described in the 1990s as a selective agonist of the peroxisome proliferator-activated receptor delta. It was studied in preclinical models for metabolic and cardiovascular conditions, but it has not been approved as a medicine in the United States, Europe, or other major jurisdictions. Retail products labeled as cardarine are generally research chemicals or supplements, not pharmaceutical formulations. Because human safety and efficacy data remain limited, regulatory agencies treat it as an unapproved substance rather than a therapeutic product.

Sporting authorities added GW501516 to prohibited lists after it appeared in athlete samples and online markets. The World Anti-Doping Agency classifies it as a hormone and metabolic modulator, and its use can lead to an anti-doping rule violation. Some early laboratory work suggested effects on fatty acid oxidation and endurance-related metabolism in animals, but those findings do not establish safe or effective use in people. Reports of adverse events in humans are scarce and often anecdotal, which complicates risk assessment.

Regulation and Analytical Detection

Anti-doping laboratories detect GW501516 and its metabolites using liquid chromatography-tandem mass spectrometry. Urine is the most common matrix, though blood and dried blood spots may also be used in some programs. Detection depends on factors such as dose, timing, metabolism, and the sensitivity of the assay. Published methods describe limits of detection in the low nanogram per milliliter range for related compounds. Exact detection windows are not fixed for all situations and remain an area of ongoing study.

Products sold as cardarine have been found to contain incorrect compounds, variable amounts, or no active ingredient at all. Independent testing is required to verify identity and purity. Common analytical approaches include high-performance liquid chromatography, mass spectrometry, and nuclear magnetic resonance for structural confirmation. These methods can distinguish GW501516 from related PPAR agonists and from unrelated steroids. For regulators and researchers, such verification is central to interpreting both biological results and adverse event reports.

Cardarine is prohibited in competitive sport under the World Anti-Doping Agency code, where it is classified as a metabolic modulator. It is not approved as a prescription medicine in the United States, European Union, or other major markets. Regulatory action has focused on its presence in sports and in products marketed as research chemicals. Because it has no accepted medical indication, supply is often unregulated. This status creates legal and safety uncertainties for anyone who encounters the substance.

Cardarine at a glance

PropertyValueNotes
IUPAC name{4-[({4-methyl-2-[4-(trifluoromethyl)phenyl]-1,3-thiazol-5-yl}methyl)sulfanyl]phenoxy}acetic acidSystematic name for GW501516
CAS Registry Number317318-70-0Unique identifier for the parent compound
Molecular formulaC21H18F3NO3S2Includes carbon, hydrogen, fluorine, nitrogen, oxygen, and sulfur
Molecular weight453.5 g/molApproximate value for the neutral form
AppearanceWhite to off-white powderTypical description for purified laboratory material

Background and Research Context

In laboratory settings, cardarine is studied as a tool compound for probing PPARδ biology. Published experiments often use cell cultures, rodent models, or isolated tissues. Some investigations focus on metabolic effects, while others assess potential risks such as carcinogenicity observed in long-term animal studies. Because human trials are sparse, most knowledge comes from preclinical work and adverse event reports. Scientific literature frequently notes the gap between animal findings and human outcomes. The compound is not a dietary supplement and is not intended for human consumption.

Cardarine is a common name for GW501516, a synthetic compound developed in the 1990s through research collaborations involving GlaxoSmithKline. It belongs to a class of molecules known as peroxisome proliferator-activated receptor delta agonists. Early studies explored its effects on lipid metabolism and energy expenditure in animal models. The compound was never approved as a human medicine, and clinical development was discontinued. In the years since, it has appeared in fitness and bodybuilding communities as a performance-enhancing substance. Regulatory agencies classify it as an unapproved drug.

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Regulation and Detection

Anti-doping laboratories identify GW501516 and related metabolites using liquid chromatography coupled with tandem mass spectrometry. Urine is the most common matrix, though blood and dried blood spots may also be analyzed. The method targets the parent compound and phase I and phase II metabolites, which extend the detection window. Because the substance is prohibited at all times, athletes can be tested outside competition. Detection limits and windows depend on the assay, sample type, and individual metabolism.

Cardarine is frequently described as a fat-burning or endurance-enhancing supplement, but these claims exceed the available evidence. The compound is not a hormone, steroid, or selective androgen receptor modulator. Research articles discuss it as a tool compound for studying PPARδ biology, while anti-doping literature focuses on its abuse and detection. Quality of unapproved products is uncertain, and independent analyses have found impurities or incorrect labeling. Open questions include whether human cancer risk resembles that seen in rodents and how often non-athletes use the substance.

Mechanism and Detection Methods

GW501516 acts as a selective agonist at PPARδ, a nuclear receptor that regulates transcription of genes involved in lipid handling and energy metabolism. Activation of PPARδ in preclinical models increases fatty acid oxidation, mitochondrial biogenesis, and exercise endurance in rodents. These effects have made the compound a subject of metabolic research and also a target for sport anti-doping rules. In humans, however, controlled studies are limited, and whether similar endurance or metabolic changes occur at tolerated exposures remains an open question. The receptor’s broad tissue distribution also means downstream effects may vary by organ and condition.

Detection of GW501516 in biological samples generally relies on liquid chromatography coupled with tandem mass spectrometry. Urine is a common matrix in anti-doping analysis, while blood or plasma may be used in research settings. Sample preparation can involve enzymatic hydrolysis, protein precipitation, or solid-phase extraction before instrumental analysis. Because the compound undergoes metabolism, assays may target the parent molecule, one or more metabolites, or both. Detection windows are not fixed; they depend on factors such as dose, route, individual metabolism, and assay sensitivity. Reference standards are required for accurate identification and quantification.

Background and Regulatory History

Cardarine is a common name for the investigational chemical GW501516, also written GW-1516. It was developed as a peroxisome proliferator-activated receptor delta agonist for metabolic conditions such as dyslipidemia. Early research focused on lipid handling and energy use in skeletal muscle and other tissues. The compound was never approved as a medicine. In public discussion, it is often grouped with performance-enhancing substances, although its receptor target differs from that of anabolic steroids or selective androgen receptor modulators. Regulatory and health authorities have issued warnings about its use.

GW501516 acts on PPARδ, a nuclear receptor that helps regulate fatty acid oxidation and energy homeostasis. In animal studies, activation of this receptor was associated with increased endurance and changes in lipid metabolism. Human trials examined effects on blood lipids and other metabolic markers, but the compound did not advance to approval. Rodent studies later reported tumors in multiple tissues at doses used in those experiments. Whether those findings translate to human risk remains uncertain, and the clinical relevance of the animal data is still debated.

Regulatory bodies treat GW501516 as a prohibited substance in competitive sport. The World Anti-Doping Agency added it to the prohibited list, and it falls under classes covering metabolic modulators and hormone-related agents. It is not approved by drug regulators for human use, and it is not a lawful dietary supplement. Products sold under the cardarine name may contain unlisted ingredients or different compounds. Because no approved product exists, quality and identity are not guaranteed by pharmaceutical manufacturing standards.

Background from the literature

One weakness of these measures is that they are not good indicators of liver vitamin A stores as retinyl esters in hepatic stellate cells. The amount of vitamin A leaving the liver, bound to retinol binding protein (RBP), is under tight control as long as there are sufficient liver reserves. Only when liver content of vitamin A drops below approximately 20 μg/gram will concentration in the blood decline.

== Histological staining == In the clinical setting, amyloid diseases are typically identified by a change in the spectroscopic properties of planar aromatic dyes such as thioflavin T, congo red or NIAD-4. In general, this is attributed to the environmental change, as these dyes intercalate between β-strands to confine their structure. Congo Red positivity remains the gold standard for diagnosis of amyloidosis. In general, binding of Congo Red to amyloid plaques produces a typical apple-green birefringence when viewed under cross-polarized light. Recently, significant enhancement of fluorescence quantum yield of NIAD-4 was exploited to super-resolution fluorescence imaging of amyloid fibrils and oligomers. To avoid nonspecific staining, other histology stains, such as the hematoxylin and eosin stain, are used to quench the dyes' activity in other places such as the nucleus, where the dye might bind. Modern antibody technology and immunohistochemistry has made specific staining easier, but often this can cause trouble because epitopes can be concealed in the amyloid fold; in general, an amyloid protein structure is a different conformation from the one that the antibody recognizes.

== Ligand variations == Since the initial MPAA ligand report, many variations of bifunctional ligands derived from amino acids have been developed. Bidentate MPAQ (mono-protected amino quinoline) ligands were introduced in the application of β-methylene C–H bonds in aliphatic amides. The highly successful MPAO (mono-protected amino oxazoline) ligand allowed for C(sp3)–H functionalization via arylation of α-methyls, borylation of cyclobutyl carboxylic amides, and boronic cross coupling of alkyl amines. MPAAM (mono-protected aminoalkyl amine) ligands were used in enantioselective C(sp3)–H arylations of free aliphatic acids without the need for exogenous directing groups. Variations of the MPAAThio (mono-protected aminoalkyl thioether) ligands have been use in olefination of free carboxylic acids and arylation, carbonylation, and olefination of free aliphatic amines. Expanding the reaction substrate scope to non-directed C(sp2)–H bonds, pyridone ligands were developed to functionalize arenes and heteroarenes which proved to be particularly useful in late-state derivatization of bioactive compounds such as estrone, caffeine, and camptothecin. Many analogues of the pyridine-pyridone (azine-pyridone) ligands were developed and used in the C(sp2)–H hydroxylation of (hetero)arenes and the dehydrogenation of methylene C(sp3)–H bonds on alkyl free acids.

== Genetics == HCP is caused by mutations in CPOX, which codes for the enzyme coproporphyrinogen oxidase. This enzyme is responsible for the sixth step in the heme biosynthetic pathway, converting coproporphyrinogen III to protoporphyrinogen IX. CPOX is located at 3q11.2-q12.1, has 6 introns and 7 exons and produces an mRNA strand that is 2675 bases in length. It is inherited in an autosomal dominant fashion, meaning that a deficiency of 50% of the normal enzyme activity is enough to cause symptoms. As reproductive fitness is not impacted, homozygous affected individuals have been reported. Along with other acute porphyrias HCP demonstrates reduced penetrance, meaning not all individuals who carry a disease-causing mutation will express symptoms. Individuals who are homozygous for a specific mutation (K404E) or compound heterozygous with a null allele in CPOX have a more severe erythropoietic porphyria, harderoporphyria, characterized by neonatal jaundice, hyperbilirubinemia, hepatosplenomegaly and skin lesions upon exposure to ultraviolet light. HCP is a rare disease, but the exact incidence is difficult to determine due to the reduced penetrance of the acute porphyrias. Overall, the incidence of all porphyrias is estimated at 1:20,000 in the United States. The incidence of harderoporphyria is even lower, with less than 10 cases reported worldwide.

Sources: en.wikipedia.org

Reference notes

2010: Law concerning "violence against women," within couples, with consequences for children, creating the offense of psychological domestic violence. 2011: Council of Europe Convention on preventing and combating violence against women and domestic violence. 2013: The ban on women wearing trousers is officially repealed. Wearing trousers had become common from the 1960s onward. 2014: Law for real equality between women and men. 2017: Starting January 1, 2017, a 40% quota on boards of directors or supervisory boards must be respected (for companies with a minimum number of employees or board members).

== Structures involved in clinical attachment loss == Clinical attachment loss refers to the apical migration and destruction of the tissues that secure the tooth within the periodontium. This process involves the coordinated breakdown of epithelial, connective tissue, and osseous components that collectively form the periodontal attachment apparatus.

=== Transfer RNAs === Other genes (MT-TH, MT-TL1, and MT-TV) encode mitochondrial specific transfer RNAs (tRNAs). Mutations in the mitochondrial MT-TL1 gene cause more than 80 percent of all cases of MELAS. This gene encodes a tRNA specific to the amino acid Leucine. These mutations impair the ability of mitochondria to make proteins, use oxygen, and produce energy. Researchers have not determined how changes in mitochondrial DNA lead to the specific signs and symptoms of MELAS. They continue to investigate the effects of mitochondrial gene mutations in different tissues, particularly in the brain.

From 1978 to 1984, the Philippine parliament was called the Batasang Pambansa (National Assembly), and its elected members were called Mambabatas Pambansa (National Assemblyman), often shortened to "MP".

Cells in the body function because of DNA. DNA sits within the nucleus of a cell. Here, parts of DNA are copied and sent to the body of the cell via RNA. The RNA is then used to create proteins, which form the basis for cells, their activity, and their products. Proteins dictate cell function and gene expression, a cell is able to self-regulate by the amount of proteins produced. However, not all cells have DNA; some cells such as mature red blood cells lose their nucleus as they mature.

Sources: en.wikipedia.org

Notes from published material

==== COX inhibitors/NSAIDs ==== Celecoxib (DFN-15; Elyxyb) – COX inhibitor/NSAID – migraine [117] Dexibuprofen (Daxfen; DexOptifen; Movone; (S)-(+)-ibuprofen; Seractil; Ultraprofen) – COX inhibitor/NSAID – headache [118]

A recent theory explores the trade-off between the relative specificity (i.e., ability to favour CO2 fixation over O2 incorporation, which leads to the energy-wasteful process of photorespiration) and the rate at which product is formed. The authors conclude that RuBisCO may actually have evolved to reach a point of 'near-perfection' in many plants (with widely varying substrate availabilities and environmental conditions), reaching a compromise between specificity and reaction rate. It has been also suggested that the oxygenase reaction of RuBisCO prevents CO2 depletion near its active sites and provides the maintenance of the chloroplast redox state. Since photosynthesis is the single most effective natural regulator of carbon dioxide in the Earth's atmosphere, a biochemical model of RuBisCO reaction is used as the core module of climate change models. Thus, a correct model of this reaction is essential to the basic understanding of the relations and interactions of environmental models.

=== 20 March === The European Union announced that it will be sending a million rounds of shells to Ukraine over the next 12 months. The United States approved a $350 million military aid package for Ukraine. The package includes ammunition for HIMARS rocket launchers, ammunition for Bradley Fighting Vehicles, HARM missiles, anti-tank weapons, riverine boats, and other equipment.

GlcNAc/NS(6S)-GlcA-GlcNS(3S,6S)-IdoA(2S)-GlcNS(6S) The conformational change in AT on heparin-binding mediates its inhibition of factor Xa. For thrombin inhibition, however, thrombin must also bind to the heparin polymer at a site proximal to the pentasaccharide. The highly negative charge density of heparin contributes to its very strong electrostatic interaction with thrombin. The formation of a ternary complex between AT, thrombin, and heparin results in the inactivation of thrombin. For this reason, heparin's activity against thrombin is size-dependent, with the ternary complex requiring at least 18 saccharide units for efficient formation. In contrast, antifactor Xa activity via AT requires only the pentasaccharide-binding site. This size difference has led to the development of low-molecular-weight heparins (LMWHs) and fondaparinux as anticoagulants. Fondaparinux targets anti-factor Xa activity rather than inhibiting thrombin activity, to facilitate a more subtle regulation of coagulation and an improved therapeutic index. It is a synthetic pentasaccharide, whose chemical structure is almost identical to the AT binding pentasaccharide sequence that can be found within polymeric heparin and heparan sulfate. With LMWH and fondaparinux, the risk of osteoporosis and heparin-induced thrombocytopenia (HIT) is reduced. Monitoring of the activated partial thromboplastin time is also not required and does not reflect the anticoagulant effect, as APTT is insensitive to alterations in factor Xa.

Sources: en.wikipedia.org

Frequently asked questions

Is cardarine approved for human use?

No. Major drug regulators have not approved GW501516 for treating any medical condition. Products sold as cardarine are typically unapproved research chemicals or supplements, so their contents and safety are not assured.

Why is cardarine banned in sport?

It is prohibited by the World Anti-Doping Agency as a hormone and metabolic modulator. Athletes who test positive for GW501516 can face sanctions, including suspensions and loss of results.

What is the difference between cardarine and GW501516?

Cardarine is a common or trade-style name, while GW501516 is the research code for the same chemical entity. Some sources also use Endurobol or GSK-516. The names refer to the same compound, not distinct drugs.

Is cardarine legal to buy?

Legal status varies by country, but cardarine is not approved as a medicine in major jurisdictions. It is often sold as a research chemical, a category that may not be lawful for human use. Buyers should check local laws and product labels carefully.

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