# Melanotan II: Research Overview — Peptide Renewal Serum > A literature summary of Melanotan II, an unapproved melanocortin receptor agonist studied for pigmentation and erectile function. Covers mechanism, trial history, and cited case reports of serious harm. A melanocortin receptor agonist studied for pigmentation and libido — unapproved anywhere, and tied to a growing case-report record of serious harm. ## The short version Melanotan II is a lab-made peptide that mimics a natural hormone, alpha-MSH, which the body uses to darken skin and hair. It was designed in the late 1980s to be a stronger, longer-lasting version of that hormone. Melanotan II activates melanocortin receptors — proteins on the surface of skin cells and in the brain. In skin cells, this switches on pigment production. In the brain, it can suppress appetite and increase sexual arousal. It has never been approved as a medicine anywhere. It reached small human trials for tanning and for erectile dysfunction decades ago and stalled there. Since then, published case reports have linked unsupervised use to new and changing moles, kidney injury, and a painful, prolonged erection called priapism. This page separates what controlled studies found from what case reports and community accounts describe — and states plainly where the serious risks lie. ## What it is Melanotan II is a cyclic, seven-amino-acid peptide: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, molecular formula C50H69N15O9. It was designed at the University of Arizona in the late 1980s as a shortened, chemically locked (cyclic) version of alpha-melanocyte-stimulating hormone (alpha-MSH), the natural pituitary hormone that governs skin and hair pigmentation. The cyclic structure and one non-standard amino-acid substitution (D-Phe in place of L-Phe) make it far more resistant to breakdown by the body's enzymes than the natural hormone, and far more potent at the receptors it binds. That resistance to breakdown is also what makes its effects — pigmentation especially — slow to fade once use stops. ## How it works Melanotan II is a non-selective agonist — it activates all five known melanocortin receptors (MC1R through MC5R) rather than just one. Activating MC1R on melanocytes, the pigment-producing cells in skin, raises a signaling molecule called cAMP inside the cell, which switches on a cascade (PKA, then CREB, then MITF) that turns up an enzyme called tyrosinase. Tyrosinase converts a precursor molecule into eumelanin, the dark skin pigment, without requiring any UV exposure to trigger it. The same non-selective activity reaches receptors outside the skin. MC4R (and MC3R) in the hypothalamus — a brain region that governs appetite and arousal — mediate the appetite-suppressing and pro-sexual effects documented in animal and early human studies [12][15]. Because one molecule activates receptors across skin, brain, and other tissue simultaneously, effects on pigmentation, appetite, and sexual function tend to appear together rather than in isolation, which is central to why its side-effect profile is broad. ## What the research shows *Oral-mucosal pigmentation, a 2026 case.* A man who self-administered Melanotan II (documented at 400 micrograms every other day for 64 days, roughly 12.8 milligrams cumulative) developed brown pigmentation on the gum tissue of both jaws and inside the cheeks. The cheek pigmentation began fading 28 days after he stopped; the gum pigmentation was still present, though lighter, at three months [11]. *Appetite suppression, mouse model.* In male mice, injecting Melanotan II directly into the nucleus accumbens — a brain region tied to reward and motivation — reduced food intake and reduced how hard the animals worked to obtain food, without triggering taste aversion or changing their metabolic rate. The effect held in both simple feeding and effort-based tests [12]. *Renal injury, a case report and review.* A published case report and literature review describes a renal infarction — a blockage of blood flow to the kidney — most likely attributable to Melanotan II use. The authors note that rhabdomyolysis (muscle breakdown) and kidney failure had previously been described with the compound, and propose that clot formation and a possible direct toxic effect on kidney tissue both need to be considered as mechanisms [13]. *Historical and regulatory lineage.* A 2006 review traces the melanocortin peptide family: Melanotan I (the linear analog) and Melanotan II (the cyclic analog covered here) were both patented and tested clinically — Melanotan I for skin tanning, Melanotan II for erectile dysfunction. A further analog derived from Melanotan II, bremelanotide, advanced through later trials and was eventually developed as a distinct, separately approved therapy for a different indication [14]. *Erectile function, a controlled human trial.* In a double-blind, placebo-controlled crossover study of 10 men with psychogenic erectile dysfunction, a subcutaneous dose of 0.025 milligrams per kilogram of body weight used in the trial produced clinically apparent erections in 8 of 10 men, with an average of 38.0 minutes of strong rigidity versus 3.0 minutes on placebo (p=0.0045). Side effects were transient nausea, stretching, and yawning that required no treatment [15]. ## Reported effects, cautions & safety *Reported effects (anecdotal, not clinical evidence):* People using Melanotan II describe a rapid, deep tan developing within days, with far less sun exposure than usual — the main reason people seek it out. Reduced appetite and some weight loss are very commonly described, often from the first dose, though people differ on whether they welcome or dislike this. Increased libido and, in men, spontaneous erections are commonly reported, sometimes at inconvenient times. The adverse side is extensive. Nausea is one of the most consistent complaints, typically worst in the first hour after a dose and in the early days of use. Facial flushing and a run-down, flu-like tiredness — nicknamed 'melanotan flu' — are commonly described early on. Spontaneous stretching and yawning after a dose is a distinctive, frequently mentioned sensation. Pigment-related reports are the most concerning cluster. Existing moles and freckles darkening is very commonly described, often the first visible sign the peptide is active. New moles appearing during use — sometimes several at once — is a frequent and alarming report among longer-term users, and is often what prompts people to see a doctor. Selective darkening of the lips, gums, scars, and genital skin is also described. The tan itself is frequently reported as uneven or blotchy, with a color that can persist for months after stopping, fading unevenly. *Cited cautions:* Because Melanotan II activates pigment-producing cells throughout the skin, published case reports describe new and changing moles, and multiple case reports document melanoma arising in people who used it — any new or changing mole during or after use warrants prompt dermatological evaluation. Renal infarction has been reported and linked to the compound's use [13]. Priapism — a prolonged, painful erection requiring emergency treatment — has been reported in multiple cases, including after apparent overdose. A case of posterior reversible encephalopathy syndrome, a brain-swelling condition, has also been reported in association with use. Because Melanotan II is unregulated, product-testing studies repeatedly find inaccurate labeling and impure content in what is sold online, compounding every other risk. It has never received regulatory approval anywhere, and its long-term safety in humans remains uncharacterized [14]. ## Where it fits in Skin & Aesthetics Melanotan II sits apart from the other two compounds on this desk. Where [GHK-Cu](/ghk-cu) and [GLOW](/glow) work on skin matrix and tissue repair, Melanotan II works on pigment production and central appetite/arousal circuits — a completely different mechanism reached through a completely different receptor family. It also carries the heaviest case-report record of harm of the three, and the least regulatory standing: no approval anywhere, versus GHK-Cu's cosmetic-ingredient status. Anyone comparing all three compounds should weigh mechanism and evidence quality separately — see the [comparison page](/compare) for that comparison side by side. ![Melanotan II research illustration — abstract dermal matrix and copper-ion motifs in emerald](/images/melanotan-2.webp) --- A citation-anchored digest on renewal-serum peptides. Not a serum. Not a clinic. Not advice.