Melanotan II

Overview

Melanotan II (also written Melanotan 2, MT-II, or MT-2) is a synthetic cyclic heptapeptide designed as an analogue of the body's natural hormone alpha-melanocyte-stimulating hormone (α-MSH). It was first synthesised at the University of Arizona in the late 1980s as part of research into peptides that could stimulate skin pigmentation (a so-called "sunless tan"). Pharmacologically it is a non-selective melanocortin receptor agonist: it activates several melanocortin receptor subtypes at once, which is the reason it produces effects on skin colour, sexual function, appetite, and the cardiovascular system rather than a single targeted action.

Melanotan II is best known today not from medicine but from its non-medical use as a tanning agent and, secondarily, for its effects on erection. Only small, early human studies were ever conducted, and the original development programme did not progress to a marketed product. Despite this, the peptide is widely sold online and through informal channels as an unregulated injectable, and its use has been documented in case reports describing serious adverse events. Multiple drug regulators have issued public warnings against using it.

Chemistry and structure

Melanotan II is a small cyclic peptide of seven amino acid residues. Unlike a simple linear peptide, it contains a ring (a lactam bridge between aspartate and lysine side chains, positions 2–7) and an acetylated N-terminus and amidated C-terminus, modifications that increase its potency and metabolic stability relative to natural α-MSH. It also incorporates a D-phenylalanine residue, a non-natural amino acid stereochemistry that further resists enzymatic breakdown.

The active His-D-Phe-Arg-Trp core derives from the conserved His-Phe-Arg-Trp sequence shared by the natural melanocortins, which is the part of the molecule recognised by melanocortin receptors. Commercial research material is usually supplied as the acetate salt.

Mechanism of action

Melanotan II works by binding to and activating melanocortin receptors (MCRs), a family of G-protein-coupled receptors that signal mainly through increased intracellular cyclic AMP (cAMP). Because Melanotan II is non-selective, it activates multiple subtypes, and its mix of effects reflects where those receptors are located in the body.

• MC1R (skin). Found on melanocytes in the skin. Activation drives synthesis of eumelanin (brown/black pigment), producing skin darkening that can occur with reduced ultraviolet (UV) exposure. This is the basis of its use as a tanning agent. The same receptor is the principal target of the approved drug afamelanotide.
• MC3R and MC4R (central nervous system). Located in the hypothalamus and spinal cord, these receptors influence sexual arousal and erection, appetite and energy balance, and autonomic (sympathetic) tone. MC4R activation in particular is linked to the spontaneous erections reported with Melanotan II.
• MC5R (exocrine and other tissues). Involved in exocrine gland function and other peripheral effects.

This broad, non-selective activation is also why the compound's side-effect profile is wide-ranging: the same receptor signalling that darkens skin also affects the brain, blood vessels, and gut. Effects such as nausea, flushing, yawning, stretching, spontaneous erections, and blood-pressure changes are direct consequences of activating melanocortin pathways that were never the intended target of a cosmetic tan.

Research and evidence

The human evidence base for Melanotan II is small, old, and limited to a few endpoints (tanning and erection). There are no large, modern, randomised controlled trials, and no completed programme led to approval. The table labels evidence type explicitly.

Skin tanning — small human studies

A pilot phase-I clinical study published in Life Sciences in 1996 (Dorr et al.) gave subcutaneous Melanotan II to three healthy male volunteers on alternating days. Two subjects developed increased pigmentation of the face, upper body, and other areas measured by quantitative reflectance, demonstrating that the peptide has genuine tanning activity in humans after only a few low doses. The same study also recorded somnolence, fatigue, and a stretching-and-yawning complex that coincided with spontaneous penile erections lasting 1–5 hours, an early signal of the compound's off-target effects. These were very small studies and were not followed by larger pigmentation trials of Melanotan II.

Erectile function — small human studies

Two studies from the University of Arizona group (Wessells et al., 2000) examined Melanotan II in men with erectile dysfunction. In a double-blind, placebo-controlled crossover design, Melanotan II initiated penile erection in the absence of sexual stimulation in a majority of men and increased self-reported sexual desire compared with placebo. Nausea and yawning were common, and severe nausea occurred in a meaningful minority at the studied dose. These results helped motivate development of a related but distinct melanocortin agonist, bremelanotide (PT-141), which was later approved for a specific form of female sexual dysfunction. Melanotan II itself was not developed into an approved erectile-dysfunction drug.

Safety and risks

This is the most important section. Melanotan II's safety profile is defined both by the intrinsic pharmacology of broad melanocortin activation and by the fact that it is almost always obtained as an unregulated, unverified product.

Common, expected effects

• Nausea and vomiting, sometimes severe; among the most frequently reported effects in both clinical studies and real-world use.
• Facial flushing.
• Loss of appetite.
• Spontaneous penile erection, yawning, and stretching shortly after dosing.
• Darkening of skin generally, plus freckles, and increased pigmentation in unexpected areas.

Priapism (prolonged, painful erection)

Beyond ordinary spontaneous erections, Melanotan II has caused priapism, a prolonged, painful erection that is a urological emergency and can cause permanent erectile damage if not treated. A case in Clinical Toxicology (Devlin et al., 2013) documented Melanotan II overdose associated with priapism, and other reports describe ischaemic priapism requiring intracavernosal medication and surgical shunting to resolve.

Moles, new nevi, and melanoma concern

Dermatologists' central worry is the compound's effect on pigmented skin lesions:

• Darkening and change of existing moles and rapid appearance of new moles, including atypical/dysplastic nevi, have been documented. One report (Actas Dermo-Sifiliográficas, 2012) described a young man who developed more than 100 melanocytic nevi, many atypical, after a four-week course.
• Melanoma has been reported in temporal association with use. A correspondence in the British Journal of Dermatology (Paurobally et al., 2011) described a melanoma arising after subcutaneous Melanotan II injections.
• The mechanistic concern is that broad melanocortin stimulation may accelerate changes in pre-existing melanocytic lesions and complicate the visual monitoring of moles, even if a direct causal role in initiating melanoma is not proven. Risk is plausibly higher in people with many moles or a family history of melanoma (for example, FAMMM syndrome).

Rare but serious systemic events

• Rhabdomyolysis and systemic toxicity. A Clinical Toxicology case (Nelson et al., 2012) described a man who injected Melanotan II purchased online and developed a sympathomimetic toxidrome with rhabdomyolysis (muscle breakdown) and renal dysfunction, requiring intensive-care management.
• Renal infarction. A CEN Case Reports paper (Peters et al., 2020) documented renal infarction in a Melanotan II user, raising concern about thrombotic and/or direct toxic effects on the kidney.
• Reversible encephalopathy. A single published case report (Kaski et al., Annals of Internal Medicine, 2013) described posterior reversible encephalopathy syndrome (PRES) associated with subcutaneous Melanotan II, and regulator summaries (e.g. the TGA) list "swelling of the brain" among possible harms. This is a rare, low-level signal, an association from isolated reports rather than an established or common effect, and tends to occur alongside hypertension.

Unregulated, contaminated, and mislabelled product

Because Melanotan II is sold outside any pharmaceutical quality system, the actual contents of a vial are uncertain. An analytical study (Breindahl et al., 2015) purchased online "10 mg" Melanotan II vials and found that every vial contained less than the labelled amount (roughly 4–9 mg), with unidentified impurities present in products from some sellers. Unsterile preparation, incorrect reconstitution, and shared or non-sterile needles add infection and dosing risks that are independent of the molecule itself.

Regulatory status and warnings

No regulator has approved Melanotan II for any use, and several have issued direct public warnings:

• United Kingdom (MHRA). The Medicines and Healthcare products Regulatory Agency has repeatedly warned against unlicensed melanotan tanning injections and nasal sprays, stating that no such product is licensed in the UK, that they may be unsafe, and that selling them is illegal. The MHRA has reported receiving suspected adverse-reaction reports and has acted against websites supplying the products.
• Australia (TGA). The Therapeutic Goods Administration warns that it is illegal to supply melanotan-containing tanning products (in any form) without a prescription, citing nausea, vomiting, facial flushing, increased moles and freckles, kidney dysfunction, brain swelling, and the risk of serious skin cancers.
• United States (FDA). Melanotan II is not an approved drug and is not a lawful dietary supplement. The FDA has long acted against unapproved injectable "tanning" products, and material is typically sold labelled "for research use only, not for human consumption."
• Other countries. National agencies in several other jurisdictions have issued comparable consumer warnings.

How it compares

These compounds are frequently confused, including in marketing, but they are not the same thing. The table compares Melanotan II with its approved relative Melanotan I (afamelanotide); the approved erectile/sexual-function melanocortin bremelanotide (PT-141) is discussed below it.

Afamelanotide (brand name Scenesse), formerly called Melanotan I, is a genuine, approved pharmaceutical. It was approved by the European Medicines Agency in 2014 and the U.S. FDA in October 2019 for a narrow indication: preventing phototoxic skin reactions in adults with erythropoietic protoporphyria (EPP), a rare inherited disorder of extreme light sensitivity. It is administered as a controlled-release implant placed by a healthcare professional, under medical supervision.

Melanotan II is different on every count: it is a smaller cyclic peptide, it is non-selective (hence the sexual and systemic effects), it has no approved medical use, and it is obtained as an unregulated injectable. The fact that an approved relative exists does not make Melanotan II safe, legitimate, or medically sanctioned.

Legal status

• United States. Not an approved drug and not a lawful dietary supplement. Unapproved injectable tanning products are subject to FDA enforcement. Commonly sold labelled "for research use only, not for human consumption."
• United Kingdom. Selling melanotan for human use is illegal; the MHRA has taken action against suppliers, and no licensed product exists.
• Australia. Supplying melanotan-containing tanning products without a prescription is illegal, per the TGA.
• Elsewhere. Generally unapproved as a medicine; national rules on import, possession, and sale of unapproved peptides vary, and several countries have issued warnings or restrictions.

This entry is educational and does not constitute legal or medical advice.

Common misconceptions

• "Melanotan II is the same as the approved Melanotan I / Scenesse." No. They are different molecules with different receptor selectivity and opposite regulatory status: afamelanotide is approved for a rare disease; Melanotan II is not approved anywhere.
• "It's a safe, natural way to tan." It is a synthetic drug that broadly activates melanocortin receptors throughout the body, with documented harms including priapism, severe nausea, mole changes, and rare serious systemic events.
• "A tan from Melanotan II protects against sun damage." Melanocortin-driven pigmentation is not a substitute for sun protection, and the compound has not been shown to safely reduce skin-cancer risk — if anything, the dermatological concern runs the other way (moles and melanoma).
• "Small clinical studies prove it's effective and fine to use." The human studies were tiny, dated, limited to narrow endpoints, and themselves reported significant side effects. They do not establish broad safety or justify unsupervised use.
• "It's regulated/quality-controlled because it's sold widely online." Analyses of online products have found underdosing and impurities; vials are not manufactured to pharmaceutical standards.

Community claims & recent evidence

These points address claims circulating in the peptide community — including popular video "masterclasses" — checked against primary sources. As with any research reagent, none of the following establishes that Melanotan II is safe or effective to use.

Verified additions

• The pro-erectile effect is a central MC4R action. [Animal] Beyond the small human ED studies above, the erection response traces to central melanocortin-4 receptor (MC4R) signalling: a selective MC4R agonist augmented erectile activity in wild-type but not Mc4r-null mice, and MC4R is expressed in penile tissue, spinal cord, and hypothalamus (Van der Ploeg et al., PNAS 2002). This is the mechanistic basis for the erections seen in humans — not evidence of a cure.
• Melanotan II suppresses appetite through the melanocortin system. [Animal] Centrally administered Melanotan II reduces food intake in rodents, an effect blocked by the MC4R antagonist SHU9119, establishing the melanocortin pathway's role in feeding and energy balance (Fan et al., Nature 1997). This explains the loss of appetite users report; it is animal pharmacology, not a human weight-loss indication.
• "Melanocortins and inflammation" is a genuine research field. [Animal] [In vitro] α-MSH and melanocortin-receptor agonists suppress pro-inflammatory signalling (e.g. NF-κB and TNF-α) and improve survival in animal models of sepsis and endotoxaemia (Catania et al., Pharmacological Reviews 2004). This is the real science the masterclass borrows from — but it concerns α-MSH and melanocortin agonists broadly, in animal and cell models, not Melanotan II as a treatment for human disease.

Claims that don't hold up

• "MT-2 treats or reverses MS, Alzheimer's, Parkinson's, type 2 diabetes, kidney disease and heart disease." [Hypothesis] No published human trial of Melanotan II exists for any of these conditions. The only human data are the small tanning and erectile-function studies already cited above. Every disease claim is an extrapolation from animal and in-vitro melanocortin-system biology onto one specific, unapproved compound — pinning a whole research field's findings onto a single product.
• "Studies show a 22% higher metabolic rate / 47% more erections / 57% better kidney filtration / 70% less brain inflammation." These precise figures, each attributed to a named university and year (Duke 2015; Amsterdam 2007; American Journal of Nephrology 2014; Journal of Neuroinflammation 2012), do not resolve to identifiable primary papers on Melanotan II. Unresolvable "a study showed X%" citations with no retrievable authors should be treated as unverified.
• "A peptide can only tell your body to do what it's designed to do — it can't force anything, and peptide deaths are precisely zero." [Human] Melanotan II has documented serious harms: priapism requiring surgical intervention, rhabdomyolysis with renal dysfunction requiring intensive care, renal infarction, and posterior reversible encephalopathy (see the Safety section). The "peptides cannot cause harm" framing directly contradicts the published case record.
• "It cures erectile dysfunction, with durable improvement long after you stop." [Hypothesis] Melanocortin agonists act on-demand; the approved relative bremelanotide (PT-141) is dosed before each occasion precisely because the effect is not durable or curative. No controlled data show lasting reversal of erectile dysfunction after discontinuing Melanotan II.
• "It readily crosses the blood–brain barrier because it's lipophilic." [Hypothesis] Melanotan II is a charged cyclic peptide; meaningful CNS penetration after peripheral dosing in humans is not established, and the sweeping neurological claims built on this premise are unverified.