melanocortin receptor 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 2026-05-06. Where a claim depends on a specific study, the study is described rather than over-claimed.
Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its structure substitutes a lactam bridge between side chains to increase stability relative to the native hormone. The compound is also known by the shorthand MT-II and by several non-proprietary synonyms used in research catalogues. It is not an approved therapeutic product in any major jurisdiction; material sold under this name is typically offered as a laboratory reagent rather than as a medicine.
Activity is attributed to agonism at melanocortin receptors, particularly MC1R and MC4R. Activation of MC1R on melanocytes increases melanin synthesis, which underlies the reported tanning effect. MC4R engagement in the central nervous system is linked to appetite suppression and to effects on sexual arousal reported in early clinical studies. Those studies were small and were not designed to establish efficacy or long-term safety. Receptor selectivity among the melanocortin subtypes is not absolute, which complicates attribution of any effect to a single pathway.
Regulatory treatment varies between countries. Several national medicines agencies have classified the peptide as unapproved, and customs authorities in some jurisdictions seize shipments on that basis. A few jurisdictions channel supply through prescription-only frameworks that do not list the substance by name. Because the material circulates mainly through online vendors, composition and purity are rarely verified before sale. Surveys of unapproved peptide products have reported labels that did not match measured content in a substantial fraction of samples.
Lyophilised melanotan-2 is supplied as a solid, which is more stable than a solution. The material is hygroscopic, so weighing is done quickly, in low humidity, with the container kept sealed. Reconstitution usually uses water for injection or bacteriostatic water, added down the wall of the vial to limit foaming. A reconstituted solution is held at 2 to 8 °C and kept away from light. Repeated freezing and thawing of the same vial is avoided because ice crystal formation and concentration effects degrade the peptide.
Reversed-phase high-performance liquid chromatography is the routine method for purity assessment. Peptides absorb near 214 nm because of the peptide bond, and a gradient of acetonitrile in water separates the intact peptide from deletion sequences, oxidised products, and earlier-eluting fragments at neutral pH. Electrospray ionisation mass spectrometry provides an orthogonal check: the measured mass must agree with the theoretical value. Amino acid analysis and peptide mapping confirm structure but are used less often. Reference standards remain scarce because the peptide is not described in any pharmacopoeia.
Regulatory treatment varies by country. In the United States the peptide is not approved as a medicine, and products offered for human use may be treated as unapproved new drugs; some states also restrict sale. Australia, the United Kingdom, and European Union member states apply comparable restrictions to unapproved peptide products. Border agencies have seized shipments labelled as research chemicals. Classification may change over time, and the legal position for personal importation is not clearly settled in most published guidance.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Analogue of alpha-melanocyte-stimulating hormone |
| Common synonyms | MT-II; melanotan 2 | No internationally accepted non-proprietary name |
| Typical presentation | Lyophilised powder in a sealed vial | Often supplied alongside a separate diluent |
| Regulatory status | Unapproved therapeutic substance | Customs seizure reported in several jurisdictions |
| Reported route in use | Subcutaneous injection | Self-administered outside clinical settings |
Melanotan-2 is a synthetic linear peptide built from seven amino acids arranged in a short chain. Its sequence is commonly written as Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2, which includes a modified N-terminus and an amidated C-terminus. The molecule belongs to the melanocortin family and acts as a receptor agonist. Structural features such as the D-phenylalanine residue and the Nle substitution are associated with increased stability against enzymatic degradation relative to the natural parent peptide.
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.
Lyophilized peptide powder is generally stored frozen, protected from light and moisture. Tryptophan residues are susceptible to oxidation, and the lactam bridge can hydrolyze under strongly acidic or basic conditions. Solutions prepared for laboratory work degrade faster than dry powder, and repeated freeze-thaw cycles accelerate loss. Common practice is to aliquot solutions before freezing and to avoid alkaline buffers. Reported stability windows vary with concentration, buffer, and temperature, so exact shelf lives are method-specific rather than universal.
Regulatory status differs by country, and in many places supplying the compound for human consumption is unlawful. Vendors frequently label material as intended for research use only, a designation that shifts stated purpose but does not create a legal pathway for personal use. Certificates of analysis accompanying such products vary widely in detail and provenance. Third-party testing exists but is voluntary, and results are rarely linked to a specific lot in a publicly verifiable way.
== Sweetness properties == On a weight basis, brazzein is 500 to 2000 times sweeter than sucrose, compared to 10% sucrose and 2% sucrose solution respectively. Its sweet perception is more similar to sucrose than that of thaumatin, with a clean sweet taste, lingering aftertaste, and slight delay (longer than aspartame) in an equi-sweet solution. Brazzein is stable over a broad pH range from 2.5 to 8, and is heat stable at 98 °C (208 °F) for 2 hours.
== Protein == The human collagen alpha-1(XXI) chain is a 957-amino acid protein. As a FACIT collagen, it has a domain organization consisting of an N-terminal signal peptide followed by a single von Willebrand factor A (VWA) domain, a thrombospondin N-terminal (TSPN) domain, and a collagen triple-helical region that is interrupted by short non-collagenous segments. This interrupted triple-helical structure is the defining feature of the FACIT subfamily, whose members associate with the surfaces of major fibril-forming collagens rather than forming fibrils on their own. The mature protein is secreted into the extracellular space and localizes to the extracellular matrix.
The epithelium of the ectocervix (the portion of the uterine cervix extending into the vagina) is an extension of, and shares a border with, the vaginal epithelium. The vaginal epithelium is made up of layers of cells, including the basal cells, the parabasal cells, the superficial squamous flat cells, and the intermediate cells. The basal layer of the epithelium is the most mitotically active and reproduces new cells. The superficial cells shed continuously and basal cells replace them. Estrogen induces the intermediate and superficial cells to fill with glycogen. Cells from the lower basal layer transition from active metabolic activity to death (apoptosis). In these mid-layers of the epithelia, the cells begin to lose their mitochondria and other organelles. The cells retain a usually high level of glycogen compared to other epithelial tissue in the body. Under the influence of maternal estrogen, the vagina of a newborn is lined by thick stratified squamous epithelium (or mucosa) for two to four weeks after birth. Between then to puberty, the epithelium remains thin with only a few layers of cuboidal cells without glycogen. The epithelium also has few rugae and is red in color before puberty. When puberty begins, the mucosa thickens and again becomes stratified squamous epithelium with glycogen-containing cells, under the influence of the girl's rising estrogen levels. Finally, the epithelium thins out from menopause onward and eventually ceases to contain glycogen, because of the lack of estrogen.
Sources: en.wikipedia.org
=== 20th-century use === Opium production in China and the rest of East Asia was nearly wiped out after WWII; however, sustained covert support by the United States Central Intelligence Agency for the Thai Northern Army and the Chinese Nationalist Kuomintang army invading Burma facilitated production and trafficking of the drug from Southeast Asia for decades, with the region becoming a major source of world supplies. During the Communist era in Eastern Europe, poppy stalks sold in bundles by farmers were processed by users with household chemicals to make kompot ("Polish heroin"), and poppy seeds were used to produce koknar, an opiate.
=== Interactions === If people are using sNRI drugs they should not take MAO inhibitors at the same time. That can increase the plasma concentration of NRIs in the body. Beware of taking atomoxetine in combination with:
=== New lethal injection protocols === The Ohio protocol, developed after the incomplete execution of Romell Broom, aims to ensure the rapid and painless onset of anesthesia by only using sodium thiopental and eliminating the use of Pavulon and potassium as the second and third drugs, respectively. It also provides for a secondary fail-safe measure using intramuscular injection of midazolam, followed by sufentanil or hydromorphone, in the event intravenous administration of the sodium thiopental proves problematic. The first state to switch to use midazolam as the first drug in a new three-drug protocol was Florida on October 15, 2013. Then on November 14, 2013, Ohio made the same move.
Sources: en.wikipedia.org
=== Targeted sanctions === In jurisdictions not subject to comprehensive sanctions, only transactions related to specific parties are prohibited. Jurisdictions that face targeted sanctions may continue to do business with the United States, with restrictions only placed on specific categories of individuals or entities, and anyone worldwide who materially supports or provides financial, logistical, or technological support for them. According to OFAC, there are approximately 12,000 names on the Specially Designated Nationals and Blocked Persons List (SDN list), which is the most restrictive category of targeted U.S. sanctions, targeting U.S.-designated terrorists, officials and beneficiaries of certain authoritarian regimes, and international criminals such as drug traffickers by blocking their U.S. assets and restricting U.S. persons from engaging in any transactions with them. The following jurisdictions have a specific OFAC sanctions program for SDN designations targeting individuals or entities engaging in sanctionable activities:
== Current use == Obsidian can be used to make extremely sharp knives, and obsidian blades are a type of glass knife made using naturally occurring obsidian instead of manufactured glass. Obsidian is used by some surgeons for scalpel blades, although this is not approved by the US Food and Drug Administration (FDA) for use on humans. Well-crafted obsidian blades, like any glass knife, can have a cutting edge many times sharper than high-quality steel surgical scalpels: the cutting edge of the blade is only about three nanometers thick. All metal knives have a jagged, irregular blade when viewed under a strong enough microscope; however, obsidian blades are still smooth, even when examined under an electron microscope. One study found that obsidian incisions produced fewer inflammatory cells and less granulation tissue in a group of rats after seven days but the differences disappeared after twenty-one days. Don Crabtree has produced surgical obsidian blades and written articles on the subject. Obsidian scalpels may be purchased for surgical use on research animals. The major disadvantage of obsidian blades is their brittleness compared to those made of metal, thus limiting the surgical applications for obsidian blades to a variety of specialized uses where this is not a concern.
Endoxifen, also known as 4-hydroxy-N-desmethyltamoxifen, is a nonsteroidal selective estrogen receptor modulator (SERM) of the triphenylethylene group as well as a protein kinase C (PKC) inhibitor. It is under development for the treatment of estrogen receptor-positive breast cancer and for the treatment of mania in bipolar disorder. It is taken by mouth. Endoxifen is an active metabolite of tamoxifen and has been found to be effective in patients that have failed previous hormonal therapies (tamoxifen, aromatase inhibitors, and fulvestrant). The prodrug tamoxifen is metabolized by the CYP2D6 enzyme to produce endoxifen and afimoxifene (4-hydroxytamoxifen). Currently, endoxifen is approved by Drugs Controller General of India for the acute treatment of manic episode with or without mixed features of Bipolar I disorder. It is manufactured and sold by Intas Pharmaceuticals under the brand name Zonalta.
=== 1974 === 16 April: Thérèse Siegenthaler (21). A sociology student at Greenwich Community College, Siegenthaler was abducted by the Wests as she hitchhiked from South London to Holyhead. Fred mistook her Swiss accent for Dutch and always referred to her as either "the Dutch girl" or "Tulip". She was reported missing to Scotland Yard by her family in Switzerland when communication from their daughter abruptly ceased. Fred later further concealed Siegenthaler's remains by building a false chimney breast on her grave. 15 November: Shirley Hubbard (15). A foster child abducted from a Droitwich bus stop close to the River Severn as she travelled home from a date. Aged 15 when murdered, Hubbard had been attending work experience in Worcester and was last seen by her boyfriend, having promised to meet him the next day. Her dismembered remains were found in a section of the cellar known to the family as the "Marilyn Monroe area". Hubbard's head had been completely covered in tape, with a one-eighth-inch (3.2 mm) diameter rubber tube inserted three inches (7.6 cm) into her nasal cavity to enable her to breathe.
Sources: en.wikipedia.org
No. No major regulatory agency has granted a marketing authorisation for melanotan II as a medicine. Products sold under this name are generally presented as laboratory reagents and are not subject to the batch-release testing applied to approved drugs.
It was developed in the 1980s by researchers investigating analogues of alpha-melanocyte-stimulating hormone for pigmentation and related endpoints. Early work included small human studies during the 1990s. Development did not progress to licensing, and the compound remained a research and grey-market item.
Peptides are prone to truncation, oxidation and aggregation during synthesis and handling. Without independent testing, a buyer cannot confirm the identity or the content of a vial. Analytical surveys of unapproved peptide products have repeatedly found discrepancies between label claims and measured composition.
Low temperature slows hydrolysis and oxidation, the two main routes by which the peptide backbone and side chains are modified. A lyophilised powder stored at −20 °C is more stable than one kept at room temperature, and once the material is dissolved the degradation rate rises, making refrigeration more important.