Everything below concerns cyclic heptapeptide. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-03-24. Numbers and descriptions here follow the published literature rather than marketing material.
Melanotan-2, also written Melanotan II, is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, and the lactam bridge between the aspartate and lysine side chains constrains the peptide into a ring. This structural change increases receptor affinity and metabolic stability relative to the native hormone. The compound was created in the 1980s as a research tool for studying pigmentation biology.
Melanocytes are the pigment-producing cells of the skin, and they carry melanocortin-1 receptors on their surface. When the receptor is activated, cyclic adenosine monophosphate rises inside the cell and raises the activity of enzymes such as tyrosinase, which increases melanin output. Melanotan-2 binds melanocortin-1 receptors in vitro and in animal models, and this binding is generally described as the basis for the tanning effect. Other receptors account for different effects: melanocortin-4 receptors contribute to appetite and erectile signalling, while melanocortin-3 and melanocortin-5 receptors contribute to energy balance and exocrine function.
Early published reports described melanotan-2 as a tanning agent without sun protection, which means darkening is not the same as protection against ultraviolet radiation. Later studies explored the peptide in erectile dysfunction, hemorrhagic shock, and some skin conditions. No regulator in the United States or Europe has approved it for clinical use. Many products labelled melanotan-2 are sold without approval and their identity and purity are unverified. Its long-term safety in humans remains an open question.
Receptor studies place melanotan-2 among non-selective melanocortin agonists, binding MC1R, MC3R, MC4R and MC5R rather than a single subtype. Activation of MC1R on cutaneous melanocytes raises tyrosinase activity and shifts pigment synthesis toward eumelanin, which is darker and more photostable than pheomelanin. Central receptors, particularly MC4R, are associated with appetite suppression and with reported effects on sexual function. Because subtype selectivity is low, the same molecule engages pigment, metabolic and vascular pathways at once, and this breadth is a common explanation offered for the range of adverse events described in user reports.
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
Melanotan-2 is a synthetic cyclic heptapeptide designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous tridecapeptide that regulates pigment production. Two modifications distinguish it from the natural hormone: norleucine replaces methionine at the N-terminus, which limits oxidation, and a D-phenylalanine substitution raises receptor affinity. The ring is closed through an aspartate-lysine lactam bridge, giving the molecule a constrained conformation. The free base has a molecular mass near 1024 daltons, and commercial material is usually supplied as an acetate salt. It appears in the literature as a research peptide rather than an approved therapeutic agent.
| Property | Value | Notes |
|---|---|---|
| Compound class | Synthetic cyclic heptapeptide | Alpha-MSH analogue containing a D-phenylalanine residue |
| Molecular formula | C50H69N15O9 | Average molecular mass approximately 1024.2 g/mol |
| Appearance | White to off-white lyophilised powder | Normally supplied as a freeze-dried solid in a sealed vial |
| Solubility | Freely soluble in water and polar solvents | Dissolves readily in aqueous buffers and in alcohol-water mixtures |
| Receptor targets | MC1R, MC3R, MC4R, MC5R | Acts as a non-selective melanocortin receptor agonist |
Published pharmacokinetic information is limited and comes mainly from small studies rather than registrational trials. Plasma half-life is usually described as short, on the order of tens of minutes, followed by rapid tissue distribution and clearance of the intact peptide. Metabolites and low concentrations of parent compound have been reported in urine, a detail relevant to anti-doping and forensic testing. Whether repeated exposure changes receptor sensitivity or clearance over time remains an open question. Values differ noticeably between analytical assays, so published numbers should be read as approximate rather than definitive.
Melanotan II is a synthetic cyclic heptapeptide with the sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, corresponding to a molecular formula of C50H69N15O9 and a monoisotopic mass near 1024 daltons. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, a peptide hormone produced by cleavage of proopiomelanocortin. A lactam bridge between the aspartate and lysine side chains closes the ring, and the C-terminal amide removes a free carboxyl group. Both modifications increase resistance to enzymatic degradation compared with the linear parent hormone. Four substitutions distinguish it from afamelanotide, the linear analogue studied under the name melanotan I.
Receptor-binding studies classify melanotan II as a non-selective melanocortin agonist. It interacts with MC1R, MC3R, MC4R and MC5R, with reported affinities in the low nanomolar range and no strong subtype preference. Activation of MC1R on dermal melanocytes shifts pigment synthesis toward eumelanin, the dark polymer deposited in melanosomes and transferred to keratinocytes. Because the same peptide engages MC4R in the hypothalamus, it also appears in animal work on food intake and erectile response, which is why it is discussed in both pigment and metabolic research. Which receptor populations dominate after systemic exposure in humans is not fully established.
The compound emerged from research programs in the 1980s that examined analogues of alpha-melanocyte-stimulating hormone for pigmentation and photoprotection. Investigators modified the native sequence to extend activity duration and potency. A related analogue, afamelanotide, was developed within the same broad line of inquiry and eventually gained approval in certain jurisdictions for a rare light-sensitivity condition. Melanotan-2 itself did not progress through the same regulatory route and has no approved therapeutic indication.
Melanocortin receptors comprise five subtypes with distinct tissue distributions and functions. Melanotan-2 is described in the literature as a non-selective agonist that engages several of these subtypes, including MC1R, MC3R, MC4R, and MC5R. MC1R is the subtype most directly linked to melanin production in skin cells. Because the compound is not subtype-selective, its observed effects in experimental settings are generally attributed to activity across multiple receptor pathways rather than to a single target.
The average 70 kg (150 lb) adult human body contains approximately 7×1027 atoms and contains at least detectable traces of 60 chemical elements. About 29 of these elements are thought to play an active positive role in life and health in humans. The relative amounts of each element vary by individual, mainly due to differences in the proportion of fat, muscle and bone in their body. Persons with more fat will have a higher proportion of carbon and a lower proportion of most other elements (the proportion of hydrogen will be about the same). The numbers in the table are averages of different numbers reported by different references. The adult human body averages ~53% water. This varies substantially by age, sex, and adiposity. In a large sample of adults of all ages and both sexes, the figure for water fraction by weight was found to be 48 ±6% for females and 58 ±8% water for males. Water is ~11% hydrogen by mass but ~67% hydrogen by atomic percent, and these numbers along with the complementary % numbers for oxygen in water, are the largest contributors to overall mass and atomic composition figures. Because of water content, the human body contains more oxygen by mass than any other element, but more hydrogen by atom-fraction than any other element.
== Role in bone decomposition == Diagenesis alters the proportions of organic collagen and inorganic components (hydroxyapatite, calcium, magnesium) of bone exposed to environmental conditions, especially moisture. This is accomplished by the exchange of natural bone constituents, deposition in voids or defects, adsorption onto the bone surface and leaching from the bone.
Cone snails are prized for their brightly colored and patterned shells, which may tempt people to pick them up. This is risky, as the snail often fires its harpoon in self defense when disturbed. The harpoons of some of the larger species of cone snail can penetrate gloves or wetsuits. The sting of many of the smallest cone species may be no worse than a bee or hornet sting, but the sting of a few of the larger tropical fish-eating species, such as Conus geographus (geography cone), Conus tulipa and Conus striatus, can be fatal. Other dangerous species are Conus pennaceus, Conus textile, Conus aulicus, Conus magus and Conus marmoreus. According to Goldfrank's Toxicologic Emergencies, about 27 human deaths can be confidently attributed to cone snail envenomation, though the actual number is almost certainly much higher; some three dozen people are estimated to have died from geography cone envenomation alone. Most of the cone snails that hunt worms are not a risk to humans, with the exception of larger species. One of the fish-eating species, the geography cone, is also known colloquially as the "cigarette snail", a gallows humor exaggeration implying that, when stung by this creature, the victim will have only enough time to smoke a cigarette before dying. Symptoms of a more serious cone snail sting include severe, localized pain, swelling, numbness and tingling, and vomiting. Symptoms can start immediately or can be delayed for days. Severe cases involve muscle paralysis, changes in vision and respiratory failure that can lead to death.
=== Marketing === Remicade is marketed by Janssen Biotech, Inc. (formerly Centocor Biotech, Inc.) in the United States, Mitsubishi Tanabe Pharma in Japan, Xian Janssen in China, and Schering-Plough (now part of Merck & Co) elsewhere.
Sources: en.wikipedia.org
γ is the ratio of the specific heats of the fluid g is the acceleration due to gravity z is the elevation of the point above a reference plane In many applications of compressible flow, changes in elevation are negligible compared to the other terms, so the term gz can be omitted. A very useful form of the equation is then:
Calcitriol is a hormone and the active form of vitamin D3, normally made in the kidney. It is also known as or 1,25-dihydroxycholecalciferol (1,25-(OH)2D3). It binds to and activates the vitamin D receptor in the nucleus of the cell, which then increases the expression of many genes. Calcitriol increases blood calcium mainly by increasing the uptake of calcium from the intestines. Calcitriol can be given as a medication for the treatment of osteoporosis, osteomalacia, familial hypophosphatemia, low blood calcium due to hypoparathyroidism, and low blood calcium and hyperparathyroidism due to kidney disease. It can be taken by mouth or by injection into a vein. Excessive amounts or intake can result in weakness, headache, nausea, constipation, urinary tract infections, and abdominal pain. Serious side effects may include high blood calcium and anaphylaxis. Calcitriol was identified as the active form of vitamin D3 in 1971 and the drug was approved for medical use in the United States in 1978. It is available as a generic medication. In 2023, it was the 249th most commonly prescribed medication in the United States, with more than 1 million prescriptions. It is on the World Health Organization's List of Essential Medicines.
Lipid-based nanoparticles are very small spherical particles composed of lipids. They are a novel pharmaceutical drug delivery system (part of nanoparticle drug delivery), and a novel pharmaceutical formulation. There are many subclasses of lipid-based nanoparticles such as: lipid nanoparticles (LNPs), solid lipid nanoparticles (SLNs), and nanostructured lipid carriers (NLCs). Sometimes the term "LNP" describes all lipid-based nanoparticles. In specific applications, LNPs describe a specific type of lipid-based nanoparticle, such as the LNPs used for the mRNA vaccine. Using LNPs for drug delivery was first approved in 2018 for the siRNA drug Onpattro. LNPs became more widely known late in 2020, as some COVID-19 vaccines that use RNA vaccine technology coat the fragile mRNA strands with PEGylated lipid nanoparticles as their delivery vehicle (including both the Moderna and the Pfizer–BioNTech COVID-19 vaccines).
The nucleoside cytosine has a half-life in isolation of 19 days at 100 °C (212 °F) and 17,000 years in freezing water, which some argue is too short on the geologic time scale for accumulation. Others have questioned whether ribose and other backbone sugars could be stable enough to be found in the original genetic material, and have raised the issue that all ribose molecules would have had to be the same enantiomer, as any nucleotide of the wrong chirality acts as a chain terminator. Pyrimidine ribonucleosides and their respective nucleotides have been prebiotically synthesised by a sequence of reactions that by-pass free sugars and assemble in a stepwise fashion by including nitrogenous and oxygenous chemistries. In a series of publications, John Sutherland and his team at the School of Chemistry, University of Manchester, have demonstrated high yielding routes to cytidine and uridine ribonucleotides built from small 2- and 3-carbon fragments such as glycolaldehyde, glyceraldehyde or glyceraldehyde-3-phosphate, cyanamide, and cyanoacetylene. One of the steps in this sequence allows the isolation of enantiopure ribose aminooxazoline if the enantiomeric excess of glyceraldehyde is 60% or greater, of possible interest toward biological homochirality. This can be viewed as a prebiotic purification step, where the said compound spontaneously crystallised out from a mixture of the other pentose aminooxazolines. Aminooxazolines can react with cyanoacetylene in a mild and highly efficient manner, controlled by inorganic phosphate, to give the cytidine ribonucleotides.
== Side effects == In September 2020, the US Food and Drug Administration (FDA) required the boxed warning be updated for all benzodiazepine medicines to describe the risks of abuse, misuse, addiction, physical dependence, and withdrawal reactions consistently across all the medicines in the class.
Sources: en.wikipedia.org
Metofoline (INN), also known as methofoline (USAN), is an opioid analgesic drug discovered in the 1950s by a team of Swiss researchers at Hoffmann-La Roche. Methopholine is an isoquinoline derivative which is not structurally related to most other opioids. However, its structural similarity to the non-opioid alkaloid papaverine is notable. Metofoline has around the same efficacy as an analgesic as codeine, and was evaluated for the treatment of postoperative pain. Metofoline tablets were marketed in the United States under the brand name of Versidyne, but the drug was withdrawn from the market in 1965 due to the occurrence of ophthalmic side-effects alongside the discovery that the drug could produce cataracts in dogs. Metofoline has two enantiomers, with the levo (R) enantiomer being the active form, around 3x the potency of codeine, and the (S) enantiomer being inactive. Analogs where the 4'-chloro group has been replaced by other electron withdrawing groups have also been tested, the fluoro derivative being slightly more potent than chloro, and the nitro derivative being most potent of all, with the racemic 4'-nitromethopholine being around 20x the potency of codeine. Later research was carried out by Bristol-Myer in the 1960s and animal studies suggested derivatives with significantly increased analgesic activity of over x50 codeine.
== Corporate Social Responsibility == As part of their Corporate Social Responsibility commitment, Hetero Group founded Sindhu Hospitals, a not-for-profit yet premium healthcare facility dedicated to providing world class healthcare underserved communities.
Chelation therapy is a medical procedure that involves the administration of chelating agents to remove or deactivate heavy metals from the body. Chelating agents are molecules that form particularly stable coordination complexes with metal ions. Complexation prevents the metal ions from reacting with molecules in the body, and enable them to be dissolved in blood and eliminated in urine.
=== Comparison of AAS === AAS differ in a variety of ways including in their capacities to be metabolized by steroidogenic enzymes such as 5α-reductase, 3-hydroxysteroid dehydrogenases, and aromatase, in whether their potency as AR agonists is potentiated or diminished by 5α-reduction, in their ratios of anabolic/myotrophic to androgenic effect, in their estrogenic, progestogenic, and neurosteroid activities, in their oral activity, and in their capacity to produce hepatotoxicity.
Sources: en.wikipedia.org
No. It is a laboratory-made peptide, while the natural hormone is alpha-melanocyte-stimulating hormone, a longer peptide produced by the pituitary gland and by skin cells. Melanotan-2 mimics only a short active region of that hormone and contains non-natural residues such as D-phenylalanine.
No approved regulatory indication exists in major markets. An approval exists for a different peptide, afamelanotide, which is used for a rare photosensitivity disorder called erythropoietic protoporphyria. Melanotan-2 itself remains a research compound with no cleared clinical role.
Melanocortin-1 receptors on melanocytes are the receptor most closely linked to pigment production. The peptide is not selective, however, and also activates melanocortin-3, melanocortin-4, and melanocortin-5 receptors. That lack of selectivity is the usual explanation offered for both its range of observed effects and its off-target effects.
No regulatory agency has authorised melanotan-2 as a medicine for any indication. It circulates mainly as a research chemical or through unregulated channels. As a result, identity, purity and content are not independently guaranteed.