MC4R 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.
Updated 2025-08-13. Numbers and descriptions here follow the published literature rather than marketing material.
Approved use is narrow and jurisdiction-specific. In the United States, the injectable product is authorised for premenopausal women with acquired, generalised hypoactive sexual desire disorder, a diagnosis that requires documented distress. It is not approved for men, for postmenopausal women, or for use alongside hormonal contraceptives under the approved labelling. Outside regulated markets, the same peptide is frequently sold as a research chemical, where identity, purity, and sterility are not independently verified.
Bremelanotide is a synthetic cyclic heptapeptide developed as an analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation and appetite signalling. Its structure contains seven amino acid residues joined by a lactam bridge that closes the ring between two side chains. The molecular formula is C50H68N14O10 and the nominal molecular mass is near 1025 daltons. Much of the early laboratory literature refers to the same molecule by the development code PT-141.
The compound emerged from a research programme examining melanocortin analogues for effects on skin pigmentation. During early human studies, participants reported spontaneous erections as an unexpected side effect, which redirected development toward sexual function rather than tanning. An intranasal formulation was investigated in clinical trials but did not reach market approval. A subcutaneous injectable version later completed the regulatory process, and the nasal route does not appear in approved labelling.
Bremelanotide is a cyclic heptapeptide that binds several melanocortin receptors rather than one. In vitro assays report agonist activity at MC1R, MC3R, MC4R and MC5R, with MC4R generally treated as the subtype most relevant to sexual effects. MC4R is expressed in hypothalamic nuclei involved in appetite, energy balance and motivated behaviour, which provides a plausible route for central action. Selective MC4R agonists studied in animals produce comparable behavioural changes, supporting that interpretation.
How receptor activation translates into a change in desire is not established in detail. Proposed steps include modulation of dopaminergic signalling in reward circuits and downstream effects on autonomic tone. Human data consist mainly of clinical trials measuring self-reported outcomes rather than direct measurements of brain activity or transmitter release. The transient rise in blood pressure sometimes observed after administration is likewise reported consistently but explained only partly by known melanocortin pathways.
Melanocortin receptors form a family of five G-protein-coupled proteins, labelled MC1R through MC5R, that respond to peptides derived from pro-opiomelanocortin. Alpha-melanocyte-stimulating hormone and adrenocorticotropic hormone are the best-known endogenous ligands. The receptors are distributed differently across tissues, so a single agonist can produce effects in the brain, skin, adrenal gland and vasculature. This distribution explains why one peptide can influence both pigmentation and motivated behaviour.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H68N14O10 | Cyclic heptapeptide backbone |
| Molecular mass | Approximately 1025 Da | Nominal mass of the free peptide |
| Appearance | White to off-white lyophilised powder | Typical for purified synthetic peptides |
| Solubility class | Freely soluble in water | Organic solubility is limited |
| Typical storage temperature | −20 °C or below | Protect from moisture and light |
From a pharmacokinetic standpoint, the peptide is usually delivered by injection because oral bioavailability is very low; proteases in the digestive tract degrade it rapidly. After subcutaneous administration, plasma concentrations reach a peak within roughly one hour. Its elimination half-life is relatively short, with most reports placing it in the range of a few hours. Nasal formulations have also been examined, though absorption varies widely between individuals. Metabolism proceeds mainly through peptidase cleavage, and the resulting products are excreted by the kidneys.
PT-141 initiates cellular signaling by binding to specific subtypes within the melanocortin receptor family. These receptors belong to the G protein-coupled receptor superfamily, and activation raises intracellular cyclic adenosine monophosphate levels. This cascade ultimately influences neuronal circuits in the central nervous system that are associated with sexual desire and arousal. Research indicates the compound's action concentrates in hypothalamic regions rather than peripheral tissues, which helps explain some observed pharmacological features. The selectivity of receptor binding underlies its functional differences.
==== Distribution ==== The volume of distribution of THC is large and is approximately 10 L/kg (range 4–14 L/kg), which is due to its high lipid solubility. The plasma protein binding of THC and its metabolites is approximately 95 to 99%, with THC bound mainly to lipoproteins and to a lesser extent albumin. THC is rapidly distributed into well-vascularized organs such as lung, heart, brain, and liver, and is subsequently equilibrated into less vascularized tissue. It is extensively distributed into and sequestered by fat tissue due to its high lipid solubility, from which it is slowly released. THC is able to cross the placenta and is excreted in human breast milk.
== E == EBIC – Electron beam induced current (see IBIC: ion beam induced charge) EBS – Elastic (non-Rutherford) backscattering spectrometry (see RBS) EBSD – Electron backscatter diffraction ECOSY – Exclusive correlation spectroscopy ECT – Electrical capacitance tomography EDAX – Energy-dispersive analysis of x-rays EDMR – Electrically detected magnetic resonance, see ESR or EPR EDS or EDX – Energy dispersive X-ray spectroscopy EELS – Electron energy loss spectroscopy EFTEM – Energy filtered transmission electron microscopy EID – Electron induced desorption EIT and ERT – Electrical impedance tomography and electrical resistivity tomography EL – Electroluminescence Electron crystallography ELS – Electrophoretic light scattering ENDOR – Electron nuclear double resonance, see ESR or EPR EPMA – Electron probe microanalysis EPR – Electron paramagnetic resonance spectroscopy ERD or ERDA – Elastic recoil detection or elastic recoil detection analysis ESCA – Electron spectroscopy for chemical analysis see XPS ESD – Electron stimulated desorption ESEM – Environmental scanning electron microscopy ESI-MS or ES-MS – Electrospray ionization mass spectrometry or electrospray mass spectrometry ESR – Electron spin resonance spectroscopy ESTM – Electrochemical scanning tunneling microscopy EXAFS – Extended X-ray absorption fine structure EXSY – Exchange spectroscopy
== Metabolism == The exact metabolic pathways of dimethocaine have not been researched, but the different metabolites have been examined in Wistar rats. After administration of dimethocaine, different metabolites have been found and identified in their urine. Due to these metabolites, different metabolic pathways could have been postulated. The main phase I reactions are ester hydrolysis, deethylation, hydroxylation of the aromatic system, or a combination of these three. The main phase II reactions are N-acetylation, glucuronidation and a combination of both. Different cytochrome P450 isozymes are involved in the initial steps of human metabolism. The N-acetylation is catalyzed by the NAT2 isozyme.
14 April GNz7q, a distant starburst galaxy, is reported as being a "missing link" between supermassive black holes and the evolution of quasars. A study describes the impact of climate change on the survival of cacti. It finds that 60% of species will experience a reduction in favourable climate by 2050–2070, with epiphytes having the greatest exposure to increased warming. A preprint demonstrates how backdoors can be placed undetectably into classifying (e.g. posts as "spam" or well-visible "not spam") machine learning models which are often developed and/or trained by third parties. Parties can change the classification of any input, including in cases with types of data/software transparency, possibly including white-box access.
Sources: en.wikipedia.org
According to historian Asif Siddiqi, Korolev's accomplishments marked "the absolute zenith of the Soviet space program, one never, ever attained since." There was a two-year pause in Soviet piloted space flights while Voskhod's replacement, the Soyuz spacecraft, was designed and developed.
=== Dried flour === In South-west Nigeria, unripe plantains are also dried and ground into flour which is referred to as Elubo Ogede. it is considered as a healthy and nutritious food among the Yoruba. In southern India, dried plantain powder is mixed with a little bit of fennel seed powder and boiled in milk or water to make baby food to feed babies until they are one year old.
In addition, the amino acid tyrosine becomes essential in people with phenylalanine hydroxylase deficiency. Thus, in addition to the careful reduction of Phe in the diet, Tyr must be supplemented to ensure that nutritional needs are met. Different people can tolerate different amounts of Phe in their diet. Regular blood tests are used to determine the effects of dietary Phe intake on blood Phe level.
==== Type distribution ==== Individual muscles tend to be a mixture of various fiber types, whose proportions vary depending on the actions of that muscle. For instance, in humans, the quadriceps muscles contain ~52% type I fibers, while the soleus is ~80% type I. The orbicularis oculi muscle of the eye is only ~15% type I. Motor units within the muscle, however, have minimal variation between the fibers of that unit. It is this fact that makes the size principle of motor unit recruitment viable. The total number of skeletal muscle fibers has traditionally been thought not to change. It is believed there are no sex or age differences in fiber distribution; however, proportions of fiber types vary considerably from muscle to muscle and person to person. Among different species there is much variation in the proportions of muscle fiber types. Sedentary men and women (as well as young children) have 45% type II and 55% type I fibers. People at the higher end of any sport tend to demonstrate patterns of fiber distribution e.g. endurance athletes show a higher level of type I fibers. Sprint athletes, on the other hand, require large numbers of type IIX fibers. Middle-distance event athletes show approximately equal distribution of the two types. This is also often the case for power athletes such as throwers and jumpers. It has been suggested that various types of exercise can induce changes in the fibers of a skeletal muscle. It is thought that by performing endurance type events for a sustained period of time, some of the type IIX fibers transform into type IIA fibers.
== Distribution among organ systems == Glucokinase has been discovered in specific cells in four types of mammalian tissue: liver, pancreas, small intestine, and brain. All play crucial roles in responding to rising or falling levels of blood glucose.
Sources: en.wikipedia.org
Varian, Inc. was one of the largest manufacturers of scientific instruments for the scientific industry. They had offerings over a broad range of chemical analysis equipment, with a particular focus on Information Rich Detection and Vacuum technology. Varian was spun off from Varian Associates in 1999 and was purchased by Agilent Technologies in May 2010 for $1.5 billion, or $52 per share. Varian Inc. had its corporate headquarters in Palo Alto, California, and offices in Australia, the Benelux countries, Brazil, Canada, China, Germany, France, Italy, Japan, Korea, Russia, Sweden, Taiwan, the United Kingdom, and the United States.
The reduced sensations can lead to injuries for either partner and their absence can make it impossible to have sexual pleasure through stimulation of the penis. Since the problems are caused by permanent nerve damage, preventive treatment through good control of the diabetes is the primary treatment. Some limited recovery may be possible through improved diabetes control. Erectile dysfunction is the inability to develop and maintain an erection sufficiently firm for satisfactory sexual performance. Diabetes is a leading cause, as is natural aging. A variety of treatments exist, most notably including the phosphodiesterase type 5 inhibitor drugs (such as sildenafil citrate, marketed as Viagra), which work by vasodilation. Priapism, a form of persistent genital arousal disorder, is a painful and potentially harmful medical condition in which the erect penis does not return to its flaccid state. Priapism lasting over four hours is a medical emergency. The causative mechanisms are poorly understood but involve complex neurological and vascular factors. Potential complications include ischaemia, thrombosis, and impotence. In serious cases the condition may result in gangrene, which may result in amputation. However, that is usually only the case if the organ is broke out and injured because of it. The condition has been associated with a variety of drugs including prostaglandin. Contrary to common knowledge, sildenafil (Viagra) will not cause it. Lymphangiosclerosis is a hardened lymph vessel, although it can feel like a hardened, almost calcified or fibrous, vein.
14 October – David Lammy becomes the first UK Foreign Secretary to attend a meeting of EU foreign ministers since Brexit as part of Labour's wish to "reset" the UK's relationship with the EU. Monarchists in Australia have criticised a decision by the country's state premieres to be absent from a reception held by Charles III when he visits the country later in the month, describing it as a snub. 16 October – The Assisted Dying Bill is introduced into Parliament, criticised by Archbishop of Canterbury Justin Welby as "dangerous" and a "slippery slope". 17 October – Former Conservative MP Craig Mackinlay is formally introduced into the House of Lords as Lord Mackinlay of Richborough. Now affectionately known as the 'bionic lord', he is the first quadruple amputee to sit in the Lords. 2024 Conservative Party leadership election: Conservative Party leadership candidates Robert Jenrick and Kemi Badenoch take part in a leadership debate on GB News, but Badenoch has turned down an invitation to take part in a Question Time special on BBC One, and a planned online debate organised by The Sun. 18 October – King Charles III and Queen Camilla arrive in Australia for their royal tour, Charles's first visit to the country since becoming King. 10 Downing Street says there will be no apology for the UK's role in the transatlantic slave trade when Charles III and Starmer attend the Commonwealth summit in Samoa. Former Daily Record editor Murray Foote announces he is standing down as chief executive of the SNP after 14 months in the post.
June 13 – 23: 2019 Men's Softball World Championship in Prague-Havlíčkův Brod Argentina defeated Japan, 3–2, to win their first Men's Softball World Championship title. Canada took third place. July 23 – 27: Europe/Africa Softball 2020 Olympic Qualifier in Utrecht Italy defeated Great Britain, 5–0, to book their team and compete at the 2020 Summer Olympics. July 26 – 30: 2019 Women's U12 Softball World Cup in Tainan (debut event) Chinese Taipei defeated Peru, 3–2, to win the inaugural Women's U12 Softball World Cup title. The Czech Republic took third place. Indonesia took fourth place. August 10 – 17: 2019 Women's U19 Softball World Cup in Irvine The United States defeated Japan, 4–3, to win their third consecutive and seventh overall Women's U19 Softball World Cup title. Canada took third place. August 25 – September 1: Americas Softball 2020 Olympic Qualifier in Surrey Champions: Mexico; Second: Canada; Third: Puerto Rico Note: Both Mexico and Canada have qualified to compete at the 2020 Summer Olympics. September 24 –28: Asia/Oceania Softball 2020 Olympic Qualifier in Shanghai Champions: Australia; Second: Chinese Taipei; Third: China Note: Australia has qualified to compete at the 2020 Summer Olympics.
Sources: en.wikipedia.org
It is a synthetic cyclic peptide that acts as an agonist at melanocortin receptors. It is not a hormone replacement therapy and not a vasodilator in the usual clinical sense, although it does affect vascular tone. Chemically it belongs to the melanocortin analogue family.
PT-141 was the internal development code used during early research and it persists in older publications, conference abstracts, and informal listings. The code and the approved name refer to the same molecule. Its continued use reflects habit in the literature rather than any difference in substance.
No. The intranasal form was studied in trials but was never approved, and absorption through the nasal route varies considerably between individuals. Approved labelling covers a subcutaneous injection only. Any nasal product sold outside regulated channels falls outside verified manufacturing.
Bremelanotide binds several melanocortin receptors, and MC4R is the subtype most often cited as responsible for its behavioural effects. Activity at MC1R, MC3R and MC5R is also reported. Selectivity is therefore described as limited rather than precise.