# Melanotan II: Research Overview > Melanotan II: Research Overview — Pussy Peptide — A cited literature summary of Melanotan II — the non-selective melanocortin agonist and PT-141's structural ancestor. Mechanism, findings, and the most serious documented safety signal of the three peptides covered here. **03 / SEXUAL & REPRODUCTIVE RESEARCH** PT-141's structural ancestor and a non-selective melanocortin agonist — the compound on this desk with the most serious documented safety record. ## The short version Melanotan II (often shortened to MT-2) is a synthetic peptide built on the same alpha-MSH backbone as PT-141, but where PT-141 was refined to act mainly on two central melanocortin receptors, Melanotan II activates all five known melanocortin receptors without much selectivity. That non-selectivity is why it darkens skin (through MC1R on pigment cells) at the same time it affects appetite and sexual arousal (through MC3R and MC4R in the brain) — three unrelated effects from one compound. It has never been approved by the FDA or any other regulator for any use. It is sold online as an unregulated tanning research chemical, and the published case-report literature documents serious harms — including new or changing moles, melanoma, kidney injury, and priapism — that are not reported at the same frequency for PT-141, its more receptor-selective, FDA-approved relative [16][15]. Nothing here is a recommendation to use it; the point of this page is to summarize what has been documented, plainly. ## What it is Melanotan II is a cyclic, lactam-bridged heptapeptide analogue of alpha-melanocyte-stimulating hormone, designed at the University of Arizona in the late 1980s for superpotent, enzyme-resistant melanotropic activity. Its sequence differs from bremelanotide's by a single terminal group — an amide in place of a carboxylic acid — which is a small structural change with a large consequence: Melanotan II keeps activity at every melanocortin receptor, while its bremelanotide derivative was selected specifically for its action at MC4R and MC3R [16]. Melanotan II is the middle link in a documented lineage: the linear analogue Melanotan I (afamelanotide) went on to FDA approval for a rare light-sensitivity condition, and a further Melanotan-II-derived analogue became bremelanotide, approved for HSDD. Melanotan II itself never advanced past small Phase 1 studies and carries no approval of its own [16]. ## How it works Melanotan II is a non-selective agonist across MC1R through MC5R. Activating MC1R on melanocytes raises intracellular cAMP and drives a signaling cascade that shifts pigment production toward eumelanin — the darker pigment — which is why it produces skin and hair darkening without sun exposure. Separately, activating central MC4R (and MC3R) in the hypothalamus and mesolimbic system is what produces the appetite-suppressing and sexual-arousal effects documented in early studies. Because one compound is engaging pigment cells, appetite circuits, and sexual-arousal circuits simultaneously, its effects are broader and less predictable than a receptor-selective compound like bremelanotide — which is the direct mechanistic reason its side-effect profile is wider. ## What the research shows A 2026 case report documented reversible oral-mucosal pigmentation in a man who self-administered Melanotan II over 64 days: brown pigmentation appeared on the gums and inner cheeks, with buccal pigmentation beginning to fade about four weeks after stopping while gum pigmentation persisted, at reduced intensity, three months out [13]. Preclinical work in mice found that Melanotan II microinjected directly into a brain reward region reduced food intake and food-seeking behavior without changing metabolic rate or producing aversion — a mechanistic look at its appetite effect [14]. On the harm side, a 2020 nephrology case report and literature review described renal infarction attributed to Melanotan II use, proposing that clot formation or a direct toxic effect on kidney tissue could explain the injury, and noting that MT-II-associated rhabdomyolysis and kidney failure had been reported previously [15]. On the effectiveness side, an early double-blind, placebo-controlled crossover study in 10 men with psychogenic erectile dysfunction found subcutaneous Melanotan II produced clinically apparent erections in 8 of 10 men, with a mean duration of significant rigidity more than twelve times longer than placebo (P=.0045); transient nausea and yawning were the accompanying side effects, requiring no treatment [17]. A historical review situates all of this within the melanocortin peptide family's development, tracing the line from Melanotan I through Melanotan II to bremelanotide and noting how differently each was ultimately used [16]. ## Reported effects, cautions & safety The reports below are anecdotal, not clinical evidence, drawn from peptide-user forums and dermatology and harm-reduction commentary rather than controlled trials, and no dose is attached to any of them. The reason most people describe seeking it out is a rapid, deep tan achieved with far less sun exposure than usual — reported as the whole point of using it. That tan comes with tradeoffs people describe often: patchy or blotchy color, an orange or grey cast rather than a natural tone, and a color that can linger for weeks to months after stopping. Reduced appetite and some weight loss are very commonly reported, sometimes from the first dose, and users are split on whether they welcome or dislike this. Men frequently describe a sudden increase in libido and spontaneous, sometimes inconveniently timed erections; women report heightened arousal as well. Nausea is one of the most consistent complaints, usually within the first hour and typically easing over the following days of use. Facial flushing, a run-down flu-like fatigue some call "melanotan flu," and an urge to stretch and yawn shortly after dosing are all frequently described. The skin effects extend well beyond the intended tan: existing moles and freckles darkening — often the first visible sign anything is happening — and, more concerning, the appearance of entirely new moles, sometimes prompting a visit to a dermatologist. Darkening has also been reported on lips, scars, and other skin areas, and injection-site irritation is common with repeated use. The published safety literature is the most serious of the three compounds on this desk. Case reports link Melanotan II use to new, changing, or dysplastic moles and, in multiple reports, to melanoma itself, attributed to its broad melanocyte-stimulating activity — any new or changing mole during or after use warrants prompt dermatological evaluation. Separate case reports describe rhabdomyolysis and acute kidney injury, and renal infarction specifically, associated with its use [15]. Priapism, a prolonged and painful erection requiring urgent treatment, has been reported in several cases, as has posterior reversible encephalopathy syndrome, a serious neurological condition involving brain swelling. Because it is sold as an unregulated research chemical, analytical testing of online and seized products has repeatedly found mislabeling and inconsistent content, which compounds every other risk. It has never been approved by any regulator and has not completed a Phase 2 or Phase 3 trial, so its long-term human safety profile remains unknown [16]. It should not be confused with the separately approved compounds descended from the same peptide family — afamelanotide (Melanotan I) and bremelanotide — whose approvals and safety data do not extend to it. ## Where it fits in sexual & reproductive research Melanotan II belongs on this desk as the cautionary counterpoint to [PT-141](/pt-141): the same alpha-MSH-derived chemistry, but without the receptor selectivity that let bremelanotide clear a regulatory review, and with a case-report safety record no other compound here approaches. It shares no receptor with [kisspeptin](/kisspeptin), which acts several steps earlier in the reproductive cascade rather than on the melanocortin system at all. Reading the three together is a way to see how much receptor selectivity and evidence maturity change the picture, even within one structurally related peptide family. See the [comparison page](/compare) for the side-by-side. --- A literature index, not a clinic and not a supplier — every claim here traces to a citation, never to us.