If you have been reading about MC4R and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-05-21. Numbers and descriptions here follow the published literature rather than marketing material.
Development began with intranasal formulations investigated for erectile dysfunction, but blood pressure elevation limited that route and prompted a switch to subcutaneous delivery. Clinical testing then shifted toward hypoactive sexual desire disorder in premenopausal women, and a subcutaneous product received United States approval in 2019. Later trials examined other populations with mixed results, and questions about effect size, durability and patient selection remain open in the peer-reviewed literature. Research interest continues in parallel with the broader melanocortin field, where several synthetic analogues are studied together.
PT-141 is the research code for bremelanotide, a cyclic heptapeptide derived from alpha-melanocyte-stimulating hormone. The molecule belongs to the melanocortin receptor agonist family and shows highest affinity for the MC4 receptor subtype, with weaker activity at MC1, MC3 and MC5. Its structure retains the core His-Phe-Arg-Trp sequence that defines melanocortin recognition, while cyclization and terminal modifications improve metabolic stability relative to the parent hormone. Early work classified the compound as a centrally acting agent rather than a peripherally acting vasodilator, which shaped subsequent development priorities.
Receptor activation in hypothalamic and limbic circuits is the mechanism most often cited for the observed effects on sexual desire. Signalling through MC4R couples to Gs proteins and raises intracellular cyclic AMP, which in turn modulates dopaminergic tone in reward-related pathways. Because the peptide reaches the central nervous system after subcutaneous administration, peripheral vascular changes are regarded as secondary rather than primary. The precise neural circuits that translate receptor occupancy into behavioural change remain incompletely mapped, and published accounts describe the pathway in general terms rather than as a fully resolved sequence.
Clinical research typically uses randomised, double-blind, placebo-controlled designs. The most common primary endpoint is the desire domain score of the Female Sexual Function Index, sometimes paired with a distress measure. Secondary outcomes include arousal, satisfaction, and event-based counts of satisfying sexual episodes. Across trials, average improvements are modest and individual responses vary widely. Whether benefits persist beyond a few months, and whether they depend on baseline hormone status, remain open questions rather than settled findings.
Melanocortin receptors form a family of five G-protein-coupled receptors designated MC1 through MC5. Bremelanotide binds most strongly at MC4R and MC1R, with weaker activity reported at MC3R and MC5R. MC4R is expressed in hypothalamic nuclei that coordinate energy balance and aspects of sexual behaviour. The prevailing interpretation is that central MC4R activation, rather than peripheral vascular effects alone, drives the reported changes in desire. This account remains partly inferential, since direct receptor-level measurement in living humans is not practical.
| Property | Value | Notes |
|---|---|---|
| Research code | PT-141 | Used in early literature before the generic name became common |
| Generic name | Bremelanotide | International nonproprietary name |
| Peptide class | Cyclic heptapeptide | Seven residues joined by a lactam bridge |
| Primary receptor | MC4R | Lower affinity reported at MC1R, MC3R and MC5R |
| Route studied clinically | Subcutaneous injection | Intranasal route was abandoned after pressor effects |
Bremelanotide is a moderately large peptide with a molecular mass near 1025 daltons. In lyophilised form it appears as a white to off-white powder and is freely soluble in water and other polar solvents. The intact lactam ring is essential for receptor affinity, while linearised fragments bind far more weakly. Solutions are sensitive to extremes of pH and to prolonged exposure to light and heat, so handling typically involves buffered conditions and cold storage. Its short plasma half-life reflects rapid distribution and clearance rather than chemical breakdown inside the vial.
Development of the peptide passed through several delivery formats, including an intranasal version tested in early trials and an injectable version that entered later clinical study. Regulatory approval for a subcutaneous product in the United States was granted in 2019 after review of controlled trials in premenopausal women. Outside the clinic, the compound circulates in research and non-pharmaceutical markets under its code name, where identity and purity vary considerably between suppliers. Synonyms appearing across technical literature include bremelanotide, PT-141, and Palatin 141.
PT-141 is the research designation for bremelanotide, a synthetic cyclic heptapeptide developed as a melanocortin receptor agonist. The peptide contains seven amino acids with an internal lactam bridge that constrains the backbone into a stable ring. Cyclisation of this kind improves resistance to enzymatic degradation relative to linear analogues. The compound was first explored for effects on melanin production, because several melanocortin receptors influence pigmentation. Its later association with sexual desire emerged from observations made during that early work, and the molecule became the subject of a separate development programme.
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.
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.
The party that were ordered last evening set out early this morning. the weather was fair and could wind N. W. about five o'clock this evening one of the wives of Charbono was delivered of a fine boy. It is worthy of remark that this was the first child which this woman had boarn and as is common in such cases her labour was tedious and the pain violent; Mr. Jessome informed me that he had freequently administered a small portion of the rattle of the rattle-snake, which he assured me had never failed to produce the desired effect, that of hastening the birth of the child; having the rattle of a snake by me I gave it to him and he administered two rings of it to the woman broken in small pieces with the fingers and added to a small quantity of water. Whether this medicine was truly the cause or not I shall not undertake to determine, but I was informed that she had not taken it more than ten minutes before she brought forth perhaps this remedy may be worthy of future experiments, but I must confess that I want faith as to it's efficacy.
Liu Wencai's administration was notorious for its corruption but effective in achieving Liu Wenhui's goals, collecting 30,000 silver dollars in its first year through the enforcement of various taxes. Liu Wencai also advised his brother to appoint loyalists as county magistrates in areas under their control, ensuring local revenue flowed directly to his forces. In Yibin, Liu Wenhui promoted modern education in both the military and civilian spheres. Also in 1922, Liu Xiang, who had become Sichuan governor, was defeated in a war against Xiong Kewu and Deng Xihou. Liu Wenhui moved his troops to Chongqing to support his nephew, but after Liu Xiang's defeat, he negotiated a withdrawal back to Yibin to avoid the loss of his army. Liu Xiang was subsequently forced to resign his position as governor. From 1922 to 1924, there was constant conflict in Sichuan. According to historian Robert Kapp, the region functioned as a politically isolated ecosystem for much of the early Republican period. Because it was insulated by geography from the rest of China, this allowed a highly fragmented and fluid balance of power to emerge against local warlords. Outside powers, including Wu Peifu of the Zhili Clique and Sun Yat-sen of the Kuomintang, also intervened intermittently in the Sichuan melee to support their chosen side in the larger context of the North-South conflict. Liu Wenhui was generally aligned with Liu Xiang and Liu Chengxun during this period, being promoted to commander of the Ninth Division in February 1923 by Liu Chengxun.
He also founded the Collective Investigation Record for the British Medical Association; this organization collected data from physicians practicing outside the hospital setting and was the precursor of modern collaborative clinical trials."
7.46 mg dihydrocodeine as co-dydramol 7.46/500 (e.g. in the branded product Paramol). 10 mg dihydrocodeine as co-dydramol 10/500, this is also the preparation to be dispensed if no strength is specified on a prescription. 20 mg dihydrocodeine as co-dydramol 20/500 (e.g. branded products Paracod 500/20 and Remedeine). 30 mg dihydrocodeine as co-dydramol 30/500 (e.g. branded products Paracod 500/30 and Remedeine Forte).
Compounding the concerns over massive pre-orders by wealthy countries, manufacturing capacity is also limited by the fact that most vaccines are patented by companies in those countries. India and South Africa proposed a waiver to the TRIPS Agreement which would remove exclusivity agreements as a barrier to setting up new facilities but the measure is being blocked by the G7.
Sources: en.wikipedia.org
=== Utopia === Comparisons are often made between the Culture and twentieth and twenty-first century Western civilisation and nation-states, particularly their interventions in less-developed societies. These are often confused with regard to the author's assumed politics. Ben Collier has said that the Culture is a utopia carrying significantly greater moral legitimacy than the West's, by comparison, proto-democracies. While Culture interventions can seem similar at first to Western interventions, especially when considered with their democratising rhetoric, the argument is that the Culture operates completely without material need, and therefore without the possibility of baser motives. This is not to say that the Culture's motives are purely altruistic; a peaceful, enlightened universe full of good neighbours lacking ethnic, religious, and sexual chauvinisms is in the Culture's interest as well. Furthermore, the Culture's ideals, in many ways similar to those of the liberal perspective today, are to a much larger extent realised internally in comparison to the West.
== Selected publications == Andrew E Clark; Erin J Kaleta; Amit Arora; Donna M Wolk (2013). "Matrix-assisted laser desorption ionization-time of flight mass spectrometry: a fundamental shift in the routine practice of clinical microbiology". Clinical Microbiology Reviews. 26 (3): 547–603. doi:10.1128/cmr.00072-12. PMC 3719498. PMID 23824373. Wikidata Q34653849. D M Wolk; M J Struelens; P Pancholi; et al. (2009). "Rapid detection of Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) in wound specimens and blood cultures: multicenter preclinical evaluation of the Cepheid Xpert MRSA/SA skin and soft tissue and blood culture assays". Journal of Clinical Microbiology. 47 (3): 823–826. doi:10.1128/jcm.01884-08. PMC 2650929. PMID 19144803. Wikidata Q41783624. Stephanie S Buehler; Bereneice Madison; Susan R Snyder; et al. (2016). "Effectiveness of Practices To Increase Timeliness of Providing Targeted Therapy for Inpatients with Bloodstream Infections: a Laboratory Medicine Best Practices Systematic Review and Meta-analysis". Clinical Microbiology Reviews. 29 (1): 59–103. doi:10.1128/cmr.00053-14. PMC 4771213. PMID 26598385. Wikidata Q26776404.
MIT.edu, OpenCourseWare: Organic Chemistry I Haverford.edu, Organic Chemistry Lectures, Videos and Text Organic-Chemistry.org, Organic Chemistry Portal – Recent Abstracts and (Name)Reactions Orgsyn.org, Organic Chemistry synthesis journal Pearson Channels, Organic Chemistry Video Lectures and Practice Problems Khanacademy.org, Khan Academy - Organic Chemistry Organic Chemistry: Structure, Function, and Practice by William Tucker Introductory Organic Chemistry by Carol Higginbotham
== History == Multiple epiphyseal dysplasia was described separately by Seved Ribbing and Harold Arthur Thomas Fairbank in the 1930s. In 1994, Ralph Oehlmann's group mapped MED to the peri-centromeric region of chromosome 19, using genetic linkage analysis. Michael Briggs' group mapped PSACH to the same area. COMP gene was firstly linked to MED and PSACH in 1995. In 1995, the group led by Knowlton did a "high-resolution genetic and physical mapping of multiple epiphyseal dysplasia and pseudoachondroplasia mutations at chromosome 19p13.1-p12." Research on COMP led to mouse models of the pathology of MED. In 2002, Svensson's group generated a COMP-null mouse to study the COMP protein in vivo. These mice showed no anatomical, histological, or even ultrastructural abnormalities and none of the clinical signs of PSACH or MED. Lack of COMP was not compensated for by any other protein in the thrombospondin family. This study confirmed that the disease is not caused by reduced expression of COMP. In 2007, Piròg-Garcia's group generated another mouse model carrying a mutation previously found in a human patient. With this new model, they were able to demonstrate that reduced cell proliferation and increased apoptosis are significant pathological mechanisms involved in MED and PSACH. In 2010, this mouse model allowed a new insight into myopathy and tendinopathy, which are often associated with PSACH and MED. These patients show increased skeletal muscle stress, as indicated by the increase in myofibers with central nuclei.
Sources: en.wikipedia.org
The code designates bremelanotide, a cyclic heptapeptide melanocortin receptor agonist. It served as an internal research identifier before the compound entered formal clinical development. The code and the generic name refer to the same molecule.
MC4R is generally described as the principal target, based on binding affinity and functional assays. Activity at MC1R, MC3R and MC5R is reported as weaker. Receptor selectivity is one reason the compound was pursued for central rather than vascular effects.
Both are synthetic melanocortin analogues built on a similar cyclic peptide scaffold. Bremelanotide is described in the literature as a metabolite-derived analogue of melanotan II rather than the same substance. The two differ in terminal modifications, which affect half-life and receptor profile.
Trial results generally show a small to moderate average improvement in desire scores relative to placebo. The distribution of responses is wide, and some participants show little measurable change. Group averages should not be read as a prediction for any single person.