This is a working overview of LC-MS/MS, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-12-21. Anything still debated is marked as such rather than presented as settled.
PPARδ is a nuclear receptor that influences transcription of genes involved in fatty acid oxidation, lipid transport, and energy homeostasis. GW501516 binds and activates this receptor with high selectivity relative to PPARα and PPARγ in laboratory assays. Activation alters expression of target genes in skeletal muscle, liver, and adipose tissue in animal models. The exact clinical consequences of these changes in humans remain incompletely characterized, and observed effects in animals do not establish therapeutic benefit or safety.
Published studies have examined GW501516 in animal models of obesity, insulin resistance, and exercise endurance. Early human trials reportedly ended, and development was discontinued after preclinical findings raised concerns about cancer in some rodent studies. Regulatory agencies have not approved cardarine for any medical use. Its availability through non-pharmaceutical channels raises questions about identity, purity, and legal status that are separate from its laboratory pharmacology. Those questions are often addressed through analytical testing rather than assumptions about product labels.
Cardarine is a common name for GW501516, also GW-1516, a synthetic compound developed as a peroxisome proliferator-activated receptor delta (PPARδ) agonist. It belongs to a class of agents that modulate gene transcription related to lipid and energy metabolism. The compound was studied in preclinical and early clinical research for metabolic and cardiovascular conditions, but it did not progress to approved therapeutic use. Its name appears in fitness and sports contexts despite not being approved as a drug.
Cardarine can be detected in biological samples and product materials using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The method separates compounds by chromatography and identifies them by mass-to-charge transitions, allowing low-level detection in urine or blood. Sample preparation often involves enzymatic hydrolysis, solid-phase extraction, or protein precipitation. Certified reference materials and isotope-labeled internal standards improve quantification. Detection windows depend on metabolism, matrix, and assay sensitivity, so no single universal window applies.
Regulatory treatment of cardarine differs by context and jurisdiction. In competitive sport, the World Anti-Doping Agency lists PPARδ agonists, including GW501516, as prohibited at all times. Outside sport, it lacks approval as a prescription medicine in major drug markets, and products sold for human consumption may be treated as unapproved drugs. Some countries also restrict importation or sale through general consumer protection and medicines laws. These classifications affect availability, testing, and legal risk without establishing therapeutic value.
Because cardarine is not an approved medicine, no pharmacopeial monograph defines its identity, purity, or storage requirements. Laboratories typically rely on in-house methods and reference standards when testing materials labeled as GW501516. Certificates of analysis may report purity and identity for a specific batch, but their scope varies and they do not guarantee safety or legal status. Independent verification can include high-performance liquid chromatography, mass spectrometry, nuclear magnetic resonance, and elemental analysis. The distinction between research chemical labeling and human use is significant because quality standards and oversight differ.
| Property | Value | Notes |
|---|---|---|
| Chemical class | PPARδ agonist | Not an anabolic steroid. |
| Common synonyms | GW501516, GW-1516 | Cardarine is an informal name. |
| Appearance | White to off-white powder | Typical for research-grade solid. |
| Solubility class | Poorly soluble in water; soluble in some organic solvents | Such as DMSO or ethanol in laboratory settings. |
| Typical storage temperature | Cool, dry, protected from light | Specific conditions vary by supplier and form. |
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.
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.
Activation of PPARδ changes transcription of genes involved in fatty acid transport, mitochondrial function, and skeletal muscle fuel preference. In rodent studies, pharmacological PPARδ activation was associated with increased endurance and altered body composition. These findings generated interest in performance enhancement, but species differences and study designs limit direct extrapolation to humans. Small human trials were conducted in the 2000s and later discontinued. The extent to which cardarine produces similar metabolic or performance effects in people remains an open question.
The compound is typically described as a laboratory compound rather than a therapeutic product. Published reports have explored its role in lipid disorders, insulin sensitivity, and exercise metabolism, yet no major drug regulator has approved it for medical use. Commercial samples sold under the cardarine name may vary in purity and identity. Analytical confirmation is therefore necessary when the material is discussed in scientific or regulatory contexts. Its classification as a prohibited substance in sport further shapes how it is studied and reported.
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.
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.
== Later research == Reichelt published a number of papers concluding that autistic children excrete higher levels of peptides in their urine, as well as that such peptides may cause autistic gaze aversion; specifically, by interfering with corticothalamocortical processing of visual stimuli. As a result of this theory, others, particularly Panksepp, have speculated that opioid antagonists such as naloxone and naltrexone may be useful in the treatment of autism. In addition, Christopher Gillberg of the University of Gothenburg has published some studies showing that animals treated with opiates exhibit less clinging, in line with the behavior of autistic children, who, his research has also shown, "do not seem concerned when their parents are not near" and "exhibit less crying than infants without autism", and has also linked an excess of endogenous opioids to stereotypic (i.e. repetitive) behavior. However, more recently, two studies were published which failed to find a difference in levels of peptides in the urine of autistic children as opposed to those without autism. A 2009 review found that no evidence exists that urinary peptide levels are correlated with gut permeability.
An analysis of Global Burden of Disease Study data estimated that about 163 million people worldwide were living with a substance use disorder in 2021, comprising roughly 111 million cases of alcohol use disorder and about 53 million of drug use disorders. Although these totals rose as the world population grew, the age-standardized prevalence rate fell by about 17% between 1990 and 2021. Prevalence peaks in young adults, at roughly 25 to 29 years, and is consistently higher among males. Age-standardized prevalence was highest in high-income North America and lowest in western sub-Saharan Africa and in north Africa and the Middle East; rates fell in most regions, but drug use disorders rose in several high-income settings. Measured as a risk factor rather than as a disorder, alcohol use was responsible for an estimated 2.6 million deaths worldwide in 2019, or 4.7% of all deaths, and psychoactive drug use for a further 0.6 million; about 2 million of the alcohol-attributable and 0.4 million of the drug-attributable deaths were among men. Alcohol-attributable burden was heaviest in countries with a low Socio-demographic Index, whereas drug-attributable burden increased with higher socio-demographic development. Between 2010 and 2023, drug use was one of only three risk factors worldwide whose age-standardized attributable DALY rate rose.
This variation resulted in some patients in slower glutathione conjugation and consequently, to a 45% increase in combined exposure to thiotepa and tepa. The volume of distribution has been reported to range from 40,8 L/m2 to 75,0 L/m2. This high value is due to the highly lipophilic character of thiotepa and can therefore easily cross cell membranes and distribute into fatty tissues. In addition, thiotepa can easily cross the blood brain barrier and can rapidly penetrate the central nervous system. In plasma, 70 to 90% of the compound remains unbound to proteins, while the remaining 10–30% is primarily bound to gamma globulin, with minimal binding to albumin. Gamma globulin primarily functions as antibodies for the immune system, while albumin serves as a transport protein. All metabolites are excreted in the urine, which is nearly complete in 6 to 8 hours, with tepa and thiotepa-mercapturate each accounting for approximately 11.1% of the excretion. In contrast, the excretion of monochloride tepa and thiotepa is significantly lower, at only 0.5% each. The total clearance of thiotepa ranged from 11,4 to 23,2 L/h/m2. The total excretion of thiotepa and its identified metabolites accounts for 54 to 100% of the total alkylating activity, suggesting the existence of other alkylating metabolites. During the conversion of glutathione conjugates into N-acetylcysteine conjugates, intermediates such as glutathione, cysteinyl glycine, and cysteine conjugates are formed.
Sources: en.wikipedia.org
However, according to Ken Gillman, the dose of cyproheptadine recommended to ensure blockade of the 5-HT2 receptors for serotonin syndrome is 20 to 30 mg based on the PET findings. Blockade of the serotonin 5-HT2B receptor may be specifically involved in the antimigraine effects of cyproheptadine. The drug has been found to prevent pergolide-induced cardiac valvulopathy, which can be assumed to be due to its serotonin 5-HT2B receptor antagonism. Cyproheptadine has been found to partially block the discriminative stimulus properties of the psychedelic drug LSD in rodent drug discrimination tests. It also antagonizes the discriminative stimulus properties of various other serotonergic agents, like 5-MeO-DMT, quipazine, fenfluramine, and 5-hydroxytryptophan (5-HTP). In addition, cyproheptadine blocks the head-twitch response induced by LSD, 5-MeO-DMT, quipazine, and 5-HTP in rodents. However, high doses of cyproheptadine have been reported to produce partial LSD-like discriminative stimulus effects in rodents. Possibly in relation to this, cyproheptadine has been said to sometimes be associated with hallucinations in humans. As an alternative possibility however, the partial generalization may instead be related to the highly non-selective nature of cyproheptadine and interactions at other neurotransmitter sites.
18 November – Researchers theorize that in many disciplines, larger scientific productivity or success by elite universities can be explained by their larger pool of available funded laborers. A commentary notes that academic rankings don't consider where (country and institute) the respective researchers were trained (1 Dec). 19 November – Researchers report determinants of alertness after waking up. 21 November Scientists in Papua New Guinea record the black-naped pheasant pigeon for the first time in 140 years. A GBD study reports the first global estimates of death rates from (33) bacterial pathogens, finding such infections are contributing to one in 8 deaths (or ~7.7 million deaths), which could make it the second largest cause of death globally in 2019. A pulsed electric field-based shark and ray bycatch mitigation device is reported, SharkGuard. 22 November The International Bureau of Weights and Measures announces it will phase out the leap second by 2035. Photochemistry is confirmed on an exoplanet for the first time, as the James Webb Space Telescope detects a range of signatures including sulfur dioxide in the atmosphere of WASP-39b. A cohort study indicates dietary intakes of total flavonols – and at least kaempferol- and quercetin-containing foods in specific – may substantially decrease decline in multiple cognitive abilities with older age, showing a difference of "0.4 units per decade" between 5 mg and 15 mg intakes.
==== Iron export ==== Iron export occurs in a variety of cell types, including neurons, red blood cells, hepatocytes, macrophages and enterocytes. The latter two are especially important since systemic iron levels depend upon them. There is only one known iron exporter, ferroportin. It transports ferrous iron out of the cell, generally aided by ceruloplasmin and/or hephaestin (mostly in enterocytes), which oxidize iron to its ferric state so it can bind ferritin in the extracellular medium. Hepcidin causes the internalization of ferroportin, decreasing iron export. Besides, hepcidin seems to downregulate both TFR1 and DMT1 through an unknown mechanism. Another player assisting ferroportin in effecting cellular iron export is GAPDH. A specific post translationally modified isoform of GAPDH is recruited to the surface of iron loaded cells where it recruits apo-transferrin in close proximity to ferroportin so as to rapidly chelate the iron extruded.
Sources: en.wikipedia.org
Cardarine is commonly known as GW501516 or GW-1516. These names refer to the same synthetic compound. It is not a brand-name approved medicine.
No, cardarine is not a steroid. It is classified as a PPARδ agonist. Its structure and receptor target differ from anabolic steroids.
No regulatory agency has approved cardarine as a medicine. It was investigated in early research but development was discontinued. It is not available as a prescription drug.
Anti-doping laboratories typically use LC-MS/MS to detect GW501516 and its metabolites in urine. The method is sensitive and can identify the compound at low concentrations. Detection depends on sample timing, metabolism, and the specific assay.