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 2026-08-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Visual description for typical solid reference material. |
| Solubility | Poorly soluble in water; soluble in DMSO | Solubility depends on solvent, purity, and form. |
| Storage | Cool, dry, protected from light | Long-term storage often uses low temperature and desiccant. |
| Common analytical method | LC-MS/MS | Used for detection and quantification in biological matrices. |
| Common synonyms | GW-501516; GW501516; endurobol | Naming varies among literature, vendors, and databases. |
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.
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.
=== 5S-GlcNAc === Ac45S-GlcNAc is converted intracellularly into UDP-5S-GlcNAc, a substrate analogue inhibitor of OGT. UDP-5S-GlcNAc is not efficiently utilized as a donor sugar by OGT, possibly due to distortion of the pyranose ring by replacement of oxygen with sulfur. As other glycosyltransferases utilize UDP-GlcNAc as a donor sugar, UDP-5S-GlcNAc has some non-specific effects on cell-surface glycosylation.
=== Myocardial excitability === Calcium (calcium chloride or calcium gluconate) reduces the cardiac toxicity of hyperkalemia by restoring normal conduction velocity. The traditional explanation held that calcium raises the threshold potential, restoring the gradient between threshold potential and resting membrane potential, which is elevated in hyperkalemia. However, a 2024 experimental study found that calcium restored cardiac conduction velocity and normalized the QRS complex without restoring resting membrane potential, suggesting the mechanism involves L-type calcium channel-dependent propagation rather than membrane potential stabilization. These findings provide a mechanistic basis for the clinical observation that calcium is most effective when ECG changes reflect conduction abnormalities (QRS widening) rather than repolarization changes alone (peaked T waves). A standard ampule of 10% calcium chloride is 10 mL and contains 6.8 mmol of calcium. A standard ampule of 10% calcium gluconate is also 10 mL but has only 2.26 mmol of calcium. Clinical practice guidelines recommend giving 6.8 mmol for typical ECG findings of hyperkalemia. This is 10 mL of 10% calcium chloride or 30 mL of 10% calcium gluconate. Though calcium chloride is more concentrated, it is caustic to veins and should generally be administered through a central line; calcium gluconate is preferred for peripheral venous access in stable patients.
=== Hormones === Estrogens are indirect anti-androgens and can be used to treat androgenetic hair loss in women with oral contraceptives. Systemic estrogen increases SHBG, which binds androgens, including testosterone and DHT, in turn reducing their bioavailability. Topical formulations are available in Europe. Hair follicles have estrogen receptors and it is theorized that topical compounds act on them directly to promote hair growth and antagonize androgen action. Large clinical studies showing effectiveness are absent. Topical treatment is also usually unavailable in North America. There is tentative evidence for cyproterone acetate in women.
Sources: en.wikipedia.org
=== Eyes === Isotretinoin and other retinoids are well known to affect the eyes. Dry eyes are very common during treatment and is caused by isotretinoin's apoptotic effect on the meibomian glands. Some people develop contact lens intolerance as a result. In some people, these changes are long-lasting or irreversible and represent Meibomian Gland Dysfunction (MGD). Other common effects on the eyes include inflammation of the eyelid (blepharitis), red eye caused by conjunctivitis and irritation of the eye. More rare ocular side effects include blurred vision, decreased night vision (which may be permanent), colour blindness, development of corneal opacities, inflammation of the cornea (keratitis), swelling of the optic disk (papilloedema, associated with IIH), photophobia and other visual disturbances.
Elaunin (Greek verb ἐλαύνω "I steer") is a component of elastic fibers formed from deposition of elastin between oxytalan fibers. It is found in the periodontal ligament and the connective tissue of the dermis, particularly in association with sweat glands.
Hepcidin is a protein that in humans is encoded by the HAMP gene. Hepcidin is a key regulator of the entry of iron into the circulation in mammals. During conditions in which the hepcidin level is abnormally high, such as inflammation, serum iron falls due to iron trapping within macrophages and liver cells and decreased gut iron absorption. This typically leads to anemia due to an inadequate amount of blood serum iron being available for developing red blood cells. When the hepcidin level is abnormally low, such as in hemochromatosis, iron overload occurs due to increased ferroportin mediated iron efflux from storage and increased gut iron absorption.
Sources: en.wikipedia.org
The reduction and subsequent reoxidation of vitamin K coupled with carboxylation of Glu is called the vitamin K cycle. Humans are rarely deficient in vitamin K because, in part, vitamin K2 is continuously recycled in cells. Warfarin and other 4-hydroxycoumarins block the action of VKOR. This results in decreased concentrations of vitamin K and vitamin K hydroquinone in tissues, such that the carboxylation reaction catalyzed by the glutamyl carboxylase is inefficient. This results in the production of clotting factors with inadequate Gla. Without Gla on the amino termini of these factors, they no longer bind stably to the blood vessel endothelium and cannot activate clotting to allow formation of a clot during tissue injury. As it is impossible to predict what dose of warfarin will give the desired degree of clotting suppression, warfarin treatment must be carefully monitored to avoid underdose and overdose.
=== Immunodeficiency === In individuals lacking functional HLA-DM molecules, improper antigen presentation occurs, resulting in unwanted immune responses or lack of a response when danger is present. This has been shown experimentally through mouse knockout models. There will be an increase of CLIP, instead of peptide, presentation on APC surfaces. This can result in autoimmunity, if a T cell receptors recognize CLIP as a harmful antigen. There could also be no protein presentation at all, resulting in a lack of immune response.
The climate of mainland Portugal and Madeira, together with their surrounding waters, is Mediterranean, whereas the Azores and its adjacent waters mainly have a temperate oceanic climate. Portugal's terrain has a diverse variety of regional climates for its size. The average temperature in Portugal varies from 4–20 °C (39.2–68.0 °F) in the mainland, around 18 °C (64.4 °F) in the Azores, and 9–19 °C (48.2–66.2 °F) in Madeira. The Iberian Peninsula is located at the southern margin of the temperate zone and at the northern margin of the subtropical high-pressure zone. Additionally, Portugal's climate is influenced by the seasonal latitudinal shift of the jet stream, which directly impacts the trajectory of the polar front. Typically in the winter, the jet stream moves southwards and Portugal comes under the influence of the polar front, producing colder temperatures. When the polar front moves northward, Portugal comes under the influence of the Azores High bringing atmospheric stability during the summer. Upwelling occurs at the coast creating the Nortada, a summer wind along the coast. Wildfires are a serious challenge in Portugal, with nearly 30% of those recorded in 2024 having an undetermined origin and arson accounting for almost five-sixths of the total burned area. Between 2014 and 2024, Portugal recorded an annual average of 12,496 fires and 112,455 ha (434 sq mi) burned, making it the European Union country with both the highest average number of wildfires and the greatest average burned area over that period.
Sources: en.wikipedia.org
Cardarine targets PPARδ, a nuclear receptor involved in lipid and energy metabolism. It does not bind the androgen receptor in the way SARMs do.
Most methods use liquid chromatography with tandem mass spectrometry. Urine is common in anti-doping testing, and blood or plasma may be used in research.
Typical guidance is cool, dry, dark storage, often at low temperature and with desiccant. Stability data are limited, so storage conditions should be verified for each batch or supplier.
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.