Is PT-141 the same as bremelanotide?

PT-141 is an older designation used in research and preclinical contexts for the compound that later entered clinical development as bremelanotide. FDA-approved bremelanotide is marketed as Vyleesi by Palatin Technologies and AMAG Pharmaceuticals. Research chemicals sold under the PT-141 label are not the same as the FDA-approved pharmaceutical product and are intended for laboratory use only.

Is Melanotan II the same as the tanning injections marketed online?

Melanotan II is the compound found in many unlicensed tanning injections sold online. It is not an approved medication in any country. Regulatory agencies including the UK Medicines and Healthcare products Regulatory Agency and the Australian Therapeutic Goods Administration have issued public warnings against its use, citing unknown purity and the lack of safety data from controlled clinical trials.

Has bremelanotide been tested in men?

The FDA approval for bremelanotide covers premenopausal women with hypoactive sexual desire disorder. Early trials in men for erectile dysfunction did not produce results sufficient for approval in that population. Research into melanocortin pathways in male sexual function continues in published literature, but bremelanotide is not currently approved for men.

Are melanocortin peptides banned by WADA?

Yes. The World Anti-Doping Agency lists melanocortin peptides and their analogs as prohibited at all times under section S2 of its Prohibited List. This applies to Melanotan II, bremelanotide, and related analogs. Athletes subject to WADA rules face anti-doping consequences for use regardless of whether the compound is from a prescription or research source.

What is the difference between afamelanotide and Melanotan II?

Afamelanotide is an MC1R-selective alpha-MSH analog approved by the FDA in 2019 as Scenesse for erythropoietic protoporphyria. Melanotan II is a non-selective cyclic analog that activates MC1R, MC3R, MC4R, and MC5R and has no regulatory approval. They share a common origin in research on alpha-MSH analogs but have different receptor selectivity, clinical evidence bases, and legal status.

Melanocortin Peptides: Melanotan II, PT-141, and the MC Receptor System

Published: April 19, 2026•Updated: April 19, 2026

Research use only. This article discusses compounds that include approved medications, investigational drugs, and research peptides. Material sold for research is not cleared for human administration and is not a substitute for medical advice.

Melanocortin peptides are a class of signaling molecules derived from a precursor protein called pro-opiomelanocortin, or POMC. They act on a family of five receptors that govern pigmentation, appetite, sexual function, inflammation, and energy expenditure. Two members of this class, Melanotan II and PT-141, are widely discussed in men's health and research communities. This article walks through how the melanocortin system actually works, what the published research shows about each compound, and how their regulatory status differs sharply from one another.

The melanocortin system in brief

Pro-opiomelanocortin is a large precursor protein produced primarily in the pituitary gland and in neurons of the hypothalamus. It is cleaved by proteases into several smaller active peptides, including adrenocorticotropin (ACTH), beta-endorphin, and the melanocyte-stimulating hormones. Alpha-MSH, the 13 amino acid fragment most relevant to this discussion, is one of the naturally occurring melanocortin ligands.

These peptides act on a family of five G protein-coupled receptors designated MC1R through MC5R. The receptors have distinct tissue distributions and physiologic roles. MC1R is expressed on melanocytes and governs skin and hair pigmentation in response to ultraviolet light. MC3R and MC4R are expressed in the brain and play central roles in energy balance and appetite regulation. MC4R is also critical for sexual arousal signaling in the central nervous system. MC5R is found in exocrine glands and has roles that are less well characterized in humans.

Where Melanotan II comes from

Melanotan II was synthesized in the 1980s and 1990s by researchers in Victor Hruby's laboratory at the University of Arizona. The goal was to create a more potent and metabolically stable analog of alpha-MSH that could be studied as a potential tanning agent or photoprotective drug. Native alpha-MSH degrades rapidly in circulation, so the Hruby group developed a cyclic analog that resists enzymatic breakdown.

Unlike alpha-MSH, which has some selectivity, Melanotan II binds MC1R, MC3R, MC4R, and MC5R with meaningful potency. This broad receptor profile means that administering it triggers multiple melanocortin pathways at once. The drug was never advanced past early clinical testing. No regulatory agency has approved Melanotan II for any indication, and it remains available only as an unlicensed research chemical.

Not to be confused with afamelanotide

Afamelanotide is a different melanocortin compound, an analog of alpha-MSH with a single amino acid substitution that makes it highly MC1R-selective and slow-releasing. It was approved by the FDA in 2019 under the name Scenesse for the prevention of phototoxic reactions in adults with erythropoietic protoporphyria, a rare metabolic disorder affecting heme synthesis. Afamelanotide and Melanotan II are pharmacologically distinct molecules with different receptor selectivity profiles and different regulatory histories.

How PT-141 differs from Melanotan II

PT-141, also known by its generic drug name bremelanotide, was derived from Melanotan II by Palatin Technologies. Researchers at Palatin identified that a ring-opened, acyclic version of the Melanotan II structure retained MC4R activity while shifting its selectivity profile. Because sexual arousal effects observed in Melanotan II research were traced primarily to MC4R activation in the central nervous system, the decision was made to develop PT-141 specifically as a treatment for sexual dysfunction.

The pharmacological profile of bremelanotide differs from Melanotan II in two meaningful ways. It is more selective at MC4R relative to MC1R, which means less potent stimulation of melanocytes. And unlike Melanotan II, bremelanotide was taken all the way through phase 3 clinical development and earned FDA approval. The drug is sold as Vyleesi.

Melanotan II

Non-selective agonist at MC1R, MC3R, MC4R, and MC5R. Developed at the University of Arizona in the 1990s. Never advanced to regulatory approval. Sold as a research chemical. Activates pigmentation, appetite, and sexual arousal pathways simultaneously.

Bremelanotide (PT-141 / Vyleesi)

Developed by Palatin Technologies from Melanotan II as a more MC4R-selective analog. FDA approved in June 2019 as Vyleesi for hypoactive sexual desire disorder in premenopausal women. Administered by subcutaneous self-injection before anticipated sexual activity. The research-chemical form sold as PT-141 is distinct from the FDA-approved drug.

Clinical trial evidence

The clinical evidence base for bremelanotide is substantially larger than for Melanotan II, because bremelanotide went through the full FDA approval process while Melanotan II did not.

Bremelanotide phase 3 trials (RECONNECT program)

Two phase 3 randomized controlled trials, called RECONNECT, studied bremelanotide in premenopausal women with hypoactive sexual desire disorder. Results published in Obstetrics and Gynecology in 2019 showed statistically significant improvements in the number of satisfying sexual events and in measures of sexual desire and distress compared with placebo, supporting the June 2019 FDA approval. The approval covered premenopausal women only.

For Melanotan II, published clinical data is limited to small early trials. Researchers at the University of Arizona published early human data in the 1990s reporting effects on pigmentation and erection in small numbers of male subjects. These studies are not the kind of large, placebo-controlled trials that establish safety and efficacy for regulatory purposes. No phase 3 program has been conducted, and no regulatory submission has been made.

Safety, side effects, and open questions

The most consistently reported adverse effects across both compounds are nausea, flushing, and headache, all effects consistent with broad melanocortin receptor activation. For approved bremelanotide, the prescribing information for Vyleesi includes a transient blood pressure increase as a notable safety signal, typically peaking around 12 minutes after injection and resolving within 12 hours, which led the FDA to recommend against use in patients with cardiovascular disease.

For Melanotan II, safety data comes largely from case reports and self-reported experiences published in the medical literature rather than from controlled clinical trials. Published reports have described spontaneous erections, darkening of existing nevi, and nausea as common occurrences. There are case reports of more serious dermatologic events, including melanoma arising in areas of unusual mole darkening in people who used Melanotan II, though establishing a causal relationship from case reports is not possible.

•Nausea is among the most commonly reported effects of both compounds across published literature
•Bremelanotide causes a transient blood pressure increase that resolves within hours per the Vyleesi prescribing information
•Melanotan II activates MC1R and may stimulate melanocyte activity, raising questions about effects on pigmented skin lesions
•Neither compound has established long-term safety data in controlled human trials beyond the approved indication for bremelanotide
•Research chemical forms of either peptide carry additional uncertainty about identity and purity without independent analytical testing

Regulatory and legal context

The regulatory positions of Melanotan II and bremelanotide diverge sharply. Bremelanotide is an FDA-approved prescription medication indicated for a specific population with a specific diagnosis. Prescribing it for other populations or indications is off-label, but the drug itself is a legitimate pharmaceutical product with a manufacturing standard and approved labeling.

Melanotan II has no approved use anywhere. Regulatory agencies in the United Kingdom, Australia, and other jurisdictions have issued warnings against its use, citing lack of safety data and concerns about melanocyte stimulation. In the United States it is not approved by the FDA for any purpose. Material sold under the Melanotan II name is sold as a research chemical for laboratory use only, and its purity and identity cannot be assumed without independent testing.

From an anti-doping standpoint, the World Anti-Doping Agency lists melanocortin peptides and their analogs as prohibited substances under its S2 category at all times. This prohibition applies to both Melanotan II and bremelanotide for athletes subject to WADA rules.