Mass spectrometry raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2025-12-21. Anything still debated is marked as such rather than presented as settled.
Stability of GW501516 depends on form, temperature, light exposure, and moisture. Solid reference material is typically stored frozen or refrigerated in a desiccator and protected from light. Solutions in organic solvents such as dimethyl sulfoxide are often kept frozen in aliquots to reduce freeze-thaw cycling. Aqueous solubility is low, so aqueous stock solutions can be difficult to prepare without cosolvents. Degradation may appear as changes in chromatographic purity or mass spectral signal. Stability studies are needed to establish shelf life for any specific preparation.
Quality assessment for cardarine samples usually combines identity, purity, and impurity testing. Nuclear magnetic resonance spectroscopy and mass spectrometry can confirm molecular structure, while high-performance liquid chromatography estimates purity. Certificates of analysis from testing laboratories may list these results, but they do not establish safety or legality. In the absence of approved manufacturing, products sold online may contain the wrong compound, variable amounts, or unlisted contaminants. Independent verification is therefore central to analytical work and to interpreting any reported biological activity.
Laboratory detection of GW501516 commonly uses liquid chromatography coupled with tandem mass spectrometry. The method can identify the parent compound or its metabolites in urine and blood after sample cleanup. Protein precipitation, solid-phase extraction, or enzymatic hydrolysis may precede analysis, depending on the matrix. Reference standards are required for accurate quantification and confirmation. Because the compound is not approved, testing often occurs in anti-doping, forensic, or research settings rather than routine clinical care. Results are reported with limits of detection and quantification.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Common for reference-grade material. |
| Solubility | Low in water | Dissolves in DMSO and some organic solvents. |
| Typical storage | -20 °C, desiccated | Protect from light and moisture. |
| Analytical method | LC-MS/MS | Used for trace detection in biological matrices. |
| Purity assessment | HPLC with UV detection | Often combined with NMR and mass spectrometry. |
Literature on cardarine often separates receptor pharmacology from toxicology. Mechanistic papers describe PPARδ activation and gene expression changes, while safety assessments focus on carcinogenicity and species differences. Questions remain about whether rodent tumors arise through PPARδ-dependent or off-target mechanisms. Another open area is how human metabolism and exposure compare with those in animal studies. Analytical methods such as liquid chromatography–mass spectrometry are used to confirm identity in biological and product samples.
GW501516 acts as an agonist at the peroxisome proliferator-activated receptor delta, a nuclear receptor that regulates gene expression. Activation shifts transcription toward genes involved in fatty acid uptake, oxidation, and energy expenditure. The compound does not bind the androgen receptor and therefore differs from anabolic steroids and SARMs. In rodent models, this metabolic shift has been linked to increased running endurance and reduced fat accumulation. The exact downstream pathways in humans remain incompletely characterized.
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.
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.
Regulatory treatment varies, but cardarine is not approved as a medicine. Sports authorities list GW501516 as a prohibited substance, and it is banned at all times under the World Anti-Doping Agency code. Many countries restrict sales for human consumption, while online vendors market it as a research chemical. Such products may lack purity data, and their actual contents can differ from the label. Purchasing or possessing cardarine may carry legal consequences depending on jurisdiction. The compound is not a dietary supplement ingredient in regulated markets.
Anti-doping laboratories identify GW501516 and its metabolites using liquid chromatography-tandem mass spectrometry. Urine is the usual matrix, and detection can occur after the parent compound has cleared from blood. The exact detection window depends on dose, formulation, individual metabolism, and assay sensitivity. Because the compound is prohibited at all times, athletes are subject to testing in and out of competition. Analytical methods continue to improve as new metabolites and designer analogs are characterized.
GW501516 acts as a ligand for PPAR delta, a nuclear receptor that regulates transcription of genes involved in fatty acid oxidation and energy use. Activation of this receptor in skeletal muscle shifts metabolism toward fat burning in animal models. The compound does not burn fat directly; it changes gene expression over hours to days. Researchers study it to understand metabolic flexibility and exercise adaptation. Effects observed in rodents are not automatically expected in humans.
Preclinical research reported that GW501516 increased running endurance in mice and improved lipid profiles in some animal species. Early human trials explored effects on high-density lipoprotein cholesterol, triglycerides, and glucose handling, but the program was discontinued. Published human data are sparse and do not establish efficacy for any condition. Studies also examined PPAR delta in cancer biology, with conflicting findings across models. The relationship between receptor activation, tissue context, and disease risk remains an active area of investigation.
Over 2000 compounds were tested randomly in a guinea pig ileum test and succinyl-L-proline was found to have the properties of a specific ACE inhibitor. It showed inhibitory effect of angiotensin I and bradykinin without having any effects on angiotensin II. Then researchers started to search for a model that would explain inhibition on the basis of specific drug interactions of compounds with the active site of ACE. Previous studies with substrates and inhibitors of ACE suggested that it was a zinc-containing metalloprotein and a carboxypeptidase similar to pancreatic carboxypeptidase A. However ACE releases dipeptides rather than single amino acids from the C-terminus of the peptide substrates. And it was assumed that both their mechanism of action and their active site might be similar. A positively charged Arg145 at the active site was thought to bind with the negatively charged C-terminal carboxyl group of the peptide substrate. It was also proposed that ACE binds by hydrogen bonding to the terminal, non scissile, peptide bond of the substrate. But since ACE is a dipeptide carboxypeptidase, unlike carboxypeptidase A, the distance between the cationic carboxyl-binding site and the zinc atom should be greater, by approximately the length of one amino acid residue. Proline was chosen as the amino acid moiety because of its presence as the carboxy terminal amino acid residue in teprotide and other ACE inhibitors found in snake venoms. Eleven other amino acids were tested but none of them were more inhibitory.
== History == In the 1940s Craig invented the first apparatus to conduct countercurrent partitioning; he called this the countercurrent distribution Craig apparatus. The apparatus consists of a series of glass tubes that are designed and arranged such that the lighter liquid phase is transferred from one tube to the next. The next major milestone was droplet countercurrent chromatography (DCCC). It uses only gravity to move the mobile phase through the stationary phase which is held in long vertical tubes connected in series. The modern era of CCC began with the development of the planetary centrifuge by Ito which was first introduced in 1966 as a closed helical tube which was rotated on a "planetary" axis as is turned on a "sun" axis. Centrifugal partition chromatography was introduced in Japan in 1982; the first instrument was built at Sanki Eng. Ltd. in Kyoto. The first instrument consisted of twelve cartridges arranged around the rotor of a centrifuge; the inner volume of each cartridge was about 15 mL for 50 channels. In 1999 Kromaton developed the first FCPC with radial cells. During cell development, the Z cell was completed in 2005 and the twin cell in 2009. In 2017 RotaChrom designed its top performing CPC cells through computed fluid dynamic simulation software by László Németh and László Lorántfy. After thousands of simulations, this tool revealed the drawbacks of conventional CPC cell designs and highlighted the unparallel load capacity and scalable cell design of RotaChrom. Both researchers left RotaChrom in Sept 1 2019.
=== Related books === In 1991, Pryor published his first book about Flag Fen, entitled Flag Fen: Prehistoric Fenland Centre, as one of a series co-produced by English Heritage and B.T. Batsford. The final monograph on the site – entitled The Flag Fen Basin: Archaeology and environment of a Fenland Landscape – was published in 2001 as an English Heritage Archaeological Report. The report is now available online through the Archaeology Data Service. Pryor has followed this with a third book on the site, published by Tempus in 2005. Entitled Flag Fen: Life and Death of a Prehistoric Landscape, it is what he has described as a "major revision" of his 1991 work, for instance repudiating his earlier "lake village" concept.
=== Lifestyle === Weight management and a healthy lifestyle are first-line treatments for PMOS. Weight management includes the prevention of weight gain, losing some weight, or maintaining weight loss. Limited weight loss of 5% shows metabolic benefits, and possibly benefits for reproductive health. There is little evidence that one type of healthy diet is better than another in PMOS. In terms of exercise, the general population guidance of 150 minutes of moderate-intensity exercise per week is recommended to prevent weight gain. For weight loss, 250 minutes of moderate exercise is recommended. Lifestyle changes for people with PMOS have been proven to be difficult due to various factors. Some studies indicate that women with PMOS might have problems with feeling sated after eating, making weight loss more challenging. Sleep disorders, more prevalent in women with PMOS, cause fatigue, which further makes a healthy lifestyle more difficult. Finally, issues with body image, eating disorders, depression, or lack of intrinsic motivation (not enjoying exercise) may make lifestyle interventions more difficult. Lifestyle interventions for women with PMOS may include strategies such as setting goals, tracking progress, learning assertiveness, and relapse prevention. These approaches aim to support weight control, a healthy lifestyle, and emotional well-being. Support may also involve using SMART goals (specific, measurable, achievable, realistic, and timely).
== Units and unit conversions == The serum concentration of prolactin can be given in mass concentration (μg/L or ng/mL), molar concentration (nmol/L or pmol/L), or international units (typically mIU/L). The current IU is calibrated against the third International Standard for Prolactin, IS 84/500. Reference ampoules of IS 84/500 contain "approximately" 2.5 μg of lyophilized human prolactin and have been assigned an activity of 0.053 International Units by calibrating against the previous standard. Measurements can be converted into mass units using this ratio of grams to IUs to obtain an equivalent in relationship to the contents of IS 84/500; prolactin concentrations expressed in mIU/L can be converted to μg/L of IS 84/500 equivalent by dividing by 21.2. Previous standards had other ratios in relation to their potency on the assay measurement. For example, the previous IS (83/562) had a potency of 27.0 mIU per μg. The first International Reference Preparation (or IRP) of human Prolactin for Immunoassay was established in 1978 (75/504 1st IRP for human prolactin) at a time when purified human prolactin was in short supply. Previous standards relied on prolactin from animal sources. Purified human prolactin was scarce, heterogeneous, unstable, and difficult to characterize. A preparation labeled 81/541 was distributed by the WHO Expert Committee on Biological Standardization without official status and given the assigned value of 50 mIU/ampoule based on an earlier collaborative study.
Sources: en.wikipedia.org
== Platforms == Current nanoparticle drug delivery systems can be cataloged based on their platform composition into several groups: polymeric nanoparticles, inorganic nanoparticles, viral nanoparticles, lipid-based nanoparticles, and nanoparticle albumin-bound (nab) technology. Each family has its unique characteristics.
where Vatom = Vcell/n and n is the number of atoms per unit cell of volume Vcell. The unit cell of silicon has a cubic packing arrangement of 8 atoms, and the unit cell volume may be measured by determining a single unit cell parameter, the length a of one of the sides of the cube. The CODATA value of a for silicon is 5.431020511(89)×10−10 m. In practice, X-ray crystallography measurements are carried out on a distance known as d220(Si), which is the distance between the planes denoted by the Miller indices {220}, and is equal to a/√8. The isotope proportional composition of the sample used must be measured and taken into account. Silicon occurs in three stable isotopes (28Si, 29Si, 30Si), and the natural variation in their proportions is greater than other uncertainties in the measurements. The atomic weight Ar for the sample crystal can be calculated, as the standard atomic weights of the three nuclides are known with great accuracy. This, together with the measured density ρ of the sample, allows the molar volume Vm to be determined:
==== Distribution ==== Following a 600 mg oral dose, peak plasma concentrations (Cmax) are achieved in approximately 2 hours under fasting conditions and 4 hours under non-fasting conditions. The presence of food alters absorption; the bioavailability of the tablet formulation decreases by 21–23% under moderate to high-fat conditions relative to fasting conditions. Ritonavir is highly bound (98–99%) to human serum proteins, primarily binding to serum albumin and α1-acid glycoprotein over a concentration range of 0.01 to 30 µg/mL. This extensive protein binding attenuates its free antiviral activity in vitro by approximately 20-fold. The drug exhibits a volume of distribution (Vd) of 0.41 ± 0.25 L/kg.
== Consumer products == There have been cases of severe contact dermatitis which was likely related to a dimethyl fumarate contact allergy of newly acquired sofas and chairs. Dimethyl fumarate has been found to be an allergic sensitizer at very low concentrations, producing eczema by contact allergy that is difficult to treat. Concentrations as low as 1 ppm (parts-per-million) may produce allergic reactions in the most severe cases. There are only a handful of equally potent sensitisers. The sensitizing risk was brought to public attention by the "poison chair" incident, where Chinese manufacturer Linkwise produced two-seater sofas with dimethyl fumarate sachets inside to inhibit mould while they were in storage or transport. In Finland where the chairs were sold from 2006 to 2007, 60 users sustained serious rashes. The cause was identified as dimethyl fumarate-induced allergic reaction by Tapio Rantanen from Finland and his original article became the cover story in the July 2008 issue of the British Journal of Dermatology. In the United Kingdom, sofas sold by Argos, Land of Leather and Walmsley Furnishing containing the chemical caused over a hundred injuries. Argos withdrew the sofas from stores and contacted buyers to collect those that had been sold — with Land of Leather withdrawing the sofas without notifying buyers and Walmsley saying they had removed the sachets from sofas they sold after the danger came to light. The danger came to public attention in 2008 when the BBC Watchdog programme alerted consumers to the sofas.
Various theories exist as to whether people who sustain carotid and vertebral artery dissection, even if they do not have a connective tissue disorder, have an underlying vulnerability. Biopsy samples of skin and other arteries has indicated that this might be a possibility, but no genetic defect in collagen or elastin genes has been convincingly proven. Other studies have indicated inflammation of the blood vessels, as measured by highly sensitive C-reactive protein (hsCRP, a marker of inflammation) in the blood. Once dissection has occurred, two mechanisms contribute to the development of stroke symptoms. Firstly, the flow through the blood vessel may be disrupted due to the accumulation of blood under the vessel wall, leading to ischemia (insufficient blood supply). Secondly, irregularities in the vessel wall and turbulence increase the risk of thrombosis (the formation of blood clots) and embolism (migration) of these clots of the brain. From various lines of evidence, it appears that thrombosis and embolism is the predominant problem. Subarachnoid hemorrhage due to arterial rupture typically occurs if the dissection extends into the V4 section of the artery. This may be explained by the fact that the arterial wall is thinner and lacks a number of structural supports in this section.
Sources: en.wikipedia.org
LC-MS/MS is common, often after sample cleanup. The assay targets GW501516 or its metabolites.
Reference material is usually kept cold, dry, and protected from light. Frozen aliquots reduce repeated freeze-thaw cycles.
No approved pharmaceutical product exists, so manufacturing and quality controls are not standardized. Products may contain different compounds or impurities.
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.