LC-MS/MS raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2025-08-17. Anything still debated is marked as such rather than presented as settled.
Clinical development stopped after rodent studies showed tumors at multiple sites. Whether those findings predict human cancer risk remains an open question, but they led sponsors to discontinue programs. Human safety data are limited to small, short-term studies that were not designed to assess cancer risk. Reported effects in those studies included changes in blood lipids, but the evidence is insufficient for medical use. Long-term consequences of nonmedical use are not well characterized. Questions about dose, duration, and individual susceptibility remain unresolved.
Cardarine is a common name for GW501516, an investigational compound developed in the 1990s for metabolic conditions. It acts as an agonist at peroxisome proliferator-activated receptor delta, a nuclear receptor involved in lipid and energy metabolism. The compound is frequently mislabeled as a selective androgen receptor modulator, or SARM, but its molecular target is different. GW501516 reached early clinical testing before development was discontinued. It has no approved therapeutic use in any country. The name cardarine is not a formal international nonproprietary name.
Handling and quality assessment of cardarine reference material follow general laboratory practices for poorly characterized compounds. It typically appears as a white to off-white powder and is sparingly soluble in water but soluble in organic solvents such as dimethyl sulfoxide and ethanol. Storage recommendations usually specify a cool, dry, dark place, with long-term storage at low temperature and desiccation. Purity may be checked by high-performance liquid chromatography with ultraviolet detection, while identity is confirmed by mass spectrometry and nuclear magnetic resonance. No pharmacopeial monograph exists, so reported purity and stability depend on the supplier’s 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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | GW501516; GW-1516; endurobol | GW501516 is the research code |
| Drug class | PPARδ agonist | Not a selective androgen receptor modulator |
| Molecular formula | C21H18F3NO3S2 | Established chemical formula |
| Molar mass | 453.5 g/mol | Calculated from the formula |
| Regulatory status | Prohibited in sport; not approved as medicine | Status varies by country |
In the fitness and bodybuilding literature, cardarine is frequently discussed as an endurance agent or fat-loss compound, although such claims are not supported by robust clinical evidence. Online descriptions often mix animal data, user anecdotes, and marketing language. Researchers who study PPARδ agonists distinguish between receptor activation in controlled experiments and unsupervised use of unverified products. The latter introduces unknown purity, dose, and interactions, making reported experiences difficult to interpret scientifically.
GW501516 acts as an agonist at peroxisome proliferator-activated receptor delta, a nuclear receptor involved in transcription of genes related to lipid handling and energy use. Activation of PPARδ can shift skeletal muscle toward greater fatty acid oxidation in animal models, which is one reason it drew interest for metabolic disease and exercise research. The exact downstream effects depend on tissue, species, dose, and duration. Human data are sparse, so many proposed benefits remain hypotheses rather than established clinical outcomes.
Laboratory studies have examined GW501516 in cell cultures and rodents for conditions such as dyslipidemia, insulin resistance, and obesity. Some trials in humans were initiated, but development was discontinued after preclinical findings raised concerns about cancer in certain models. Those findings do not prove that the compound causes cancer in people, but they contributed to regulatory caution. Later reviews often describe the evidence as preliminary and insufficient for assessing long-term safety.
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.
Cardarine has no approved therapeutic indication and is not marketed as a medicine. The World Anti-Doping Agency lists GW501516 as a prohibited substance at all times, covering both in-competition and out-of-competition periods. National laws vary: some countries treat it as an unapproved drug subject to import controls, while others have specific restrictions on sale for human consumption. It is often sold as a research chemical, a label that does not imply safety or legality. Enforcement actions have targeted online vendors and shipments.
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.
A persistent misconception is that cardarine is a fat-burning drug or a safe alternative to anabolic steroids. No approved therapeutic product exists, and human safety data are limited. The tumor findings in rodents remain a central concern in scientific reviews. Products sold online may contain inaccurate labels, impurities, or different compounds entirely, which complicates any assessment of effects. Independent testing of such products has reported frequent mislabeling. For these reasons, discussions in the literature emphasize risks and unknowns rather than benefits.
Cardarine is not approved for human therapeutic use in any major jurisdiction. It appears on the World Anti-Doping Agency Prohibited List as a PPARδ agonist within the hormone and metabolic modulators category. Sports organizations test for it because it has been detected in athlete samples and seized products. Regulatory actions against marketed research chemical versions have occurred in several countries, though enforcement varies. Availability through unregulated channels complicates oversight.
Analytical laboratories typically identify cardarine and its metabolites using liquid chromatography-tandem mass spectrometry. Urine is a common matrix in anti-doping testing, while blood and tissue may be used in research settings. Detection windows depend on the assay, the sample matrix, and the compound's metabolism. Because cardarine is extensively metabolized, laboratories often target specific metabolites to improve sensitivity and confirmation. Reference standards are required for reliable quantification. Method validation includes checks for selectivity, linearity, and carryover.
Inherited – hereditary motor neuropathies, Charcot–Marie–Tooth disease, and hereditary neuropathy with liability to pressure palsy Acquired – diabetes mellitus, vascular neuropathy, alcohol use disorder, vitamin E deficiency, and vitamin B12 deficiency
=== Prosecution in Panama === Noriega was tried in absentia in Panama for crimes committed during his rule. In October 1993 Noriega and two others were convicted of the murder of Spadafora by the court of the Third Judicial District, and sentenced to 20 years in prison. Panama's Supreme Court confirmed the sentence on December 20, 1995. In 1994, Noriega and Heráclides Sucre, an agent of his secret police, were convicted by a jury of the murder of Giroldi, who had led the 1989 coup attempt against Noriega. Though Noriega was tried in absentia, a judge traveled to the U.S. to question him in December 1993. Noriega and Sucre both received a 20-year sentence, the maximum penalty sought by the prosecutor. Finally, Noriega received a third 20-year sentence in 1996 for his role in the death of nine military officers supporting Giroldi; the group had been executed in a hangar at the Albrook air base after the coup attempt, in an incident that came to be known as the massacre of Albrook. Noriega was also prosecuted over the 1968 disappearances of Luis Antonio Quirós and Everett Clayton Kimble Guerra in Chiriquí, and the 1971 death of Heliodoro Portugal. These cases had not reached a conclusion at the time of his death in 2017.
== Mechanism of action == Golodirsen has been provisionally approved for approximately 8% of all people with Duchenne muscular dystrophy amenable to exon 53 skipping. It works by inducing exon skipping in the dystrophin gene and thereby increasing the amount of dystrophin protein available to muscle fibers.
=== Mechanism of action === Fialuridine (FIAU) is thymidine-like nucleoside analogue that was investigated as an antiviral against hepatitis B virus (HBV). HBV replication depends on its viral polymerase, which acts as reverse transcriptase and makes viral DNA. Because FIAU-TP resembles the normal nucleotide TTP, the viral polymerase can use FIAU-TP as an alternative substrate during DNA synthesis. This disrupts replication in two related ways. Fist, FIAU-TP can directly inhibit hepatitis virus DNA polymerase activity (shown in the duck hepatitis B virus model). Second, FIAU-TP interferes with the early protein-priming stage of reverse transcription. In an in-vitro priming system, FIAU-TP caused premature termination of the short starter DNA, which prevents proper extension into full-length viral DNA. Importantly, FIAU is not a classic obligate chain terminator, because it still has an intact 3’-OH group. However, once FIAU is incorporated into the growing DNA strand, extension becomes strongly slowed or blocked after a short step, so it behaves as a ‘de facto’ chain terminator. So FIAU's antiviral action can be summarized as follows: after FIAU is converted inside the cell into the active triphosphate form FIAU-TP, it can be used by the viral polymerase during BHV reverse transcription. This interaction disrupts the priming step and subsequent DNA chain synthesis, which eventually reduces the formation of complete viral DNA genomes.
=== Discovery === Meitnerium was first synthesized on August 29, 1982, by a German research team led by Peter Armbruster and Gottfried Münzenberg at the Institute for Heavy Ion Research (Gesellschaft für Schwerionenforschung) in Darmstadt. The team bombarded a target of bismuth-209 with accelerated nuclei of iron-58 and detected a single atom of the isotope meitnerium-266:
Sources: en.wikipedia.org
GLP1 poly-agonist peptides are a class of drugs that activate multiple peptide hormone receptors including the glucagon-like peptide-1 (GLP-1) receptor. These drugs are developed for the same indications as GLP-1 receptor agonists—especially obesity, type 2 diabetes, and non-alcoholic fatty liver disease. Unlike GLP-1 mono-agonists, which target only the GLP-1 receptor, poly-agonists activate two or more incretin receptors, such as the gastric inhibitory polypeptide (GIP) receptor, which have distinct features but work together in metabolic regulation. GIP and GLP-1 are both naturally released from the gastrointestinal tract after eating, but act on different receptor distributions across tissues. GLP-1 receptors are concentrated in the pancreas, brain, and gastrointestinal tract, while GIP receptors are found primarily in the pancreas, brain, and adipose tissue. In healthy people, the combined incretin effect of GIP and GLP-1 accounts for around 50–70% of post-meal insulin secretion. This effect is substantially reduced in people with type 2 diabetes, providing evidence for therapies that activate both hormones. Poly-agonists are expected to provide superior efficacy with fewer adverse effects compared to GLP-1 mono-agonists, which are dose-limited by gastrointestinal disturbances. The effectiveness of multi-receptor agonists could possibly equal or exceed that of bariatric surgery. The first such drug to receive approval is tirzepatide, a dual agonist of GLP-1 and GIP receptors.
In cladistics, a homoplasy is a trait shared by two or more taxa for any reason other than that they share a common ancestry. Taxa which do share ancestry are part of the same clade; cladistics seeks to arrange them according to their degree of relatedness to describe their phylogeny. Homoplastic traits caused by convergence are therefore, from the point of view of cladistics, confounding factors which could lead to an incorrect analysis.
Sweden's Flygvapnet first recuperated four of the P-51s (two P-51Bs and two early P-51Ds) that had been diverted to Sweden during missions over Europe. In February 1945, Sweden purchased 50 P-51Ds designated J 26, which were delivered by American pilots in April and assigned to the Uppland Wing (F 16) at Uppsala as interceptors. In early 1946, the Jämtland Wing (F 4) at Östersund was equipped with a second batch of 90 P-51Ds. A final batch of 21 Mustangs was purchased in 1948. In all, 161 J 26s served in the Swedish Air Force during the late 1940s. About 12 were modified for photo reconnaissance and redesignated S 26. Some of these aircraft participated in the secret Swedish mapping of new Soviet military installations at the Baltic coast in 1946–47 (Operation Falun), an endeavor that entailed many intentional violations of Soviet airspace. However, the Mustang could outdive any Soviet fighter of that era, so no S 26s were lost in these missions. The J 26s were replaced by De Havilland Vampires around 1950. The S 26s were replaced by S 29Cs in the early 1950s. Switzerland
Michael Andrew Fischbach (born November 3, 1980) is an American chemist, microbiologist, and geneticist. He is an associate professor of Bioengineering and ChEM-H Faculty Fellow at Stanford University and a Chan Zuckerberg Biohub Investigator.
=== Specific activity === The specific activity of an enzyme is another common unit. This is the activity of an enzyme per milligram of total protein (expressed in μmol min−1 mg−1). Specific activity gives a measurement of enzyme purity in the mixture. It is the micro moles of product formed by an enzyme in a given amount of time (minutes) under given conditions per milligram of total proteins. Specific activity is equal to the rate of reaction multiplied by the volume of reaction divided by the mass of total protein. The SI unit is katal/kg, but a more practical unit is μmol/(mg*min). Specific activity is a measure of enzyme processivity (the capability of enzyme to be processed), at a specific (usually saturating) substrate concentration, and is usually constant for a pure enzyme. An active site titration process can be done for the elimination of errors arising from differences in cultivation batches and/or misfolded enzyme and similar issues. This is a measure of the amount of active enzyme, calculated by e.g. titrating the amount of active sites present by employing an irreversible inhibitor. The specific activity should then be expressed as μmol min−1 mg−1 active enzyme. If the molecular weight of the enzyme is known, the turnover number, or μmol product per second per μmol of active enzyme, can be calculated from the specific activity. The turnover number can be visualized as the number of times each enzyme molecule carries out its catalytic cycle per second.
Sources: en.wikipedia.org
=== Metabolism === Cholesterol is recycled in the body. The liver excretes cholesterol into biliary fluids, which are then stored in the gallbladder from where they are excreted in a non-esterified form (via bile) into the digestive tract. Typically, about 50% of the excreted cholesterol is reabsorbed by the small intestine back into the bloodstream.
=== Main === Callum McGowan as Vikram Chamberlain, the active Librarian of 1847 who is released from a timeless imprisonment in 2025 and takes up work as the head Librarian of the Belgrade Annex. He is renowned as one of the greatest swordfighters in the world and carries a sword sheathed in a cane, while his first name is non-Anglophone due to his being born in India. Olivia Morris as: Dr. Lysa Pascal, a mathematician, engineer, and physicist who inherits a castle in Belgrade which hosts an Annex to the Library. She is initially skeptical of the existence of magic but comes to accept it as real while still perceiving it as an untapped branch of science. Anya, General Bogdan Gregor's fiancée and Vikram's lover, who is also Lysa's direct ancestor Bluey Robinson as Connor Green, an expert historian and disgraced university professor-turned-Internet video-streaming conspiracy theorist with a large following, who discovers the Library out of his determination to prove that it exists Jessica Green as Charlie Cornwall, a U.S. military veteran and Guardian candidate who is given a second chance by Jacob Stone and charged with protecting Vikram, Lysa, and Connor
=== Microscopy === Culture techniques will often use a microscopic examination to help in the identification of the microbe. Instruments such as compound light microscopes can be used to assess critical aspects of the organism. This can be performed immediately after the sample is taken from the patient and is used in conjunction with biochemical staining techniques, allowing for resolution of cellular features. Electron microscopes and fluorescence microscopes are also used for observing microbes in greater detail for research. The two main types of electron microscopy are scanning electron microscopy and transmission electron microscopy. Transmission electron microscopy passes electrons through a thin cross-section of the cell of interest, and it then redirects the electrons onto a fluorescent screen. This method is useful for looking at the inside of cells, and the structures within, especially cell walls and membranes. Scanning electron microscopy reads the electrons that are reflected off the surface of the cells. A 3-dimensional image is then made which shows the size and exterior structure of the cells. Both techniques help give more detailed information about the structure of microbes. This makes it useful in many medical fields, such as diagnostics and biopsies of many body parts, hygiene, and virology. They provide critical information about the structure of pathogens, which allow physicians to treat them with more knowledge.
Opioid switching, also called opioid rotation, is the replacement of the current opioid with another pharmacological agent such as morphine or methadone. It was effective in some studies, but can increase sensitivity to pain, requiring higher doses of the opioid-sparing drug. Opioid rotation is a safe and effective alternative to completely stopping opioid therapy. Methadone is also believed to show some efficacy in OIH, presumably due to its weak NMDA antagonist activity. Ketamine, an NMDA antagonist, has been shown to prevent the extended use of opioid in post-operative hyperalgesia when it is infused in a small amount perioperatively along with the opioid but there are also studies that show ketamine being ineffective in modulating hyperalgesia. The use of an NSAID, especially some COX-2 inhibitors, or acetaminophen either as monotherapy or combination therapy is also suggested as a possible treatment option.
=== Crash === Soon after the big boom, the first problems started to appear. There were problems getting products approved by the FDA and if they got approved there were often difficulties in getting insurance providers to pay for the products and getting it accepted by health care providers. For example, organogenesis ran into problems marketing its product and integrating its product in the health system. This partially due to the difficulties of handling living cells and the increased difficulties faced by physicians in using these products over conventional methods. Another example would be Advanced Tissue Sciences Dermagraft skin product which could not create a high enough demand without reimbursements from insurance providers. Reasons for this were $4000 price-tag and the circumstance that Additionally Advanced Tissue Sciences struggled to get their product known by physicians. The above examples demonstrate how companies struggled to make profit. This, in turn, lead investors to lose patience and stopping further funding. In consequence, several Tissue Engineering companies such as Organogenesis and Advanced Tissue Sciences filed for bankruptcy in the early 2000s. At this time, these were the only ones having commercial skin products on the market.
Sources: en.wikipedia.org
No. Cardarine is GW501516, a PPARδ agonist, while SARMs act on androgen receptors. The two classes are often grouped in informal discussions despite different mechanisms.
No. It has no approved medical indication in any country. Regulatory agencies have not cleared it for treatment or prevention of any condition.
Early clinical work stopped after rodent carcinogenicity findings. Those animal results raised concerns about long-term human risk, although direct human evidence is lacking. The human relevance of the tumors remains an open scientific question.
Cardarine targets PPARδ, a nuclear receptor involved in lipid and energy metabolism. It does not bind the androgen receptor in the way SARMs do.