Melanotan 2 (Melanotan II): Complete Research Guide and Documented Risks

The body has five melanocortin receptors. MC2R, the adrenal ACTH receptor, responds essentially only to ACTH; the other four — MC1R, MC3R, MC4R and MC5R — all recognise α-MSH and superpotent analogues such as melanotan II. MT-II is therefore a non-selective agonist, and the receptors it switches on serve very different systems, from pigmentation and energy balance to sexual function and exocrine gland secretion.^[8][3][7]

MC1R sits on melanocytes, where activation increases melanin production — the basis of MT-II's tanning effect. MC3R and MC4R are mainly expressed in the brain. In mice, MT-II delivered into the brain suppressed feeding in four different models of overeating, an effect completely blocked by SHU9119. Genetic, pharmacological and receptor-mapping work in mice, rats and human tissue shows that MC4R also modulates erectile function through spinal and penile nerve pathways.^{[12][8][10][11]}

The practical consequence is that MT-II cannot act on skin alone. The same molecule that darkens skin also reaches the receptors behind appetite, nausea and arousal — which is exactly the combination of effects the human studies recorded.^[4][5][3]

The first human study, published in 1996, was a single-blind pilot phase I trial in three healthy men, alternating MT-II and saline days over two weeks at low, weight-based doses. Mild nausea occurred at most dose levels, and one volunteer had grade II sleepiness and fatigue at the top dose. A stretching-and-yawning complex tracked with spontaneous erections lasting one to five hours, and two of the three men had measurably increased pigmentation of the face, upper body and buttocks a week after the last administration.^[4]

Two small placebo-controlled crossover trials in men with erectile dysfunction followed. In ten men with psychogenic ED, eight developed clinically apparent erections on MT-II, with a mean 38 minutes of more than 80% tip rigidity against 3 minutes on placebo. In ten men with organic risk factors, erections followed 12 of 19 MT-II administrations versus 1 of 21 on placebo and sexual desire rose — but 4 of the 19 caused severe nausea.^[5][6][7]

Across the combined 20 men, nausea and yawning were the characteristic side effects. These studies — around two dozen men, each exposed for a single session or up to two weeks, with no women and no long-term follow-up — form the core of MT-II's controlled human data. Development then moved to its derivative PT-141 rather than to larger MT-II trials, and clinicians reviewing later misuse describe the drug as unlicensed and incompletely tested.^[7][2][18]

Melanotan I, now called afamelanotide, is the linear 13-amino-acid analogue [Nle4, D-Phe7]-α-MSH — the programme's regulated success. The EMA authorised it in December 2014, under exceptional circumstances, as an implant (Scenesse) to prevent or reduce light-induced symptoms in erythropoietic protoporphyria, a rare disease of light intolerance.^[1][2][13]

Bremelanotide (PT-141) is MT-II's closest regulated relative: the same acetylated cyclic heptapeptide, but ending in a free carboxylic acid instead of an amide. The FDA approved it in 2019 (Vyleesi) for acquired, generalised hypoactive sexual desire disorder in premenopausal women. Its label documents the class effects under controlled conditions: nausea in 40% of patients, transient rises in blood pressure, and focal hyperpigmentation of the face, gums and breasts.^[12][4][2]

The contrast is the point. Afamelanotide and bremelanotide went through controlled development and regulatory review for one indication each; melanotan II did not. Their safety data describe those molecules, not MT-II, and a dermatology review draws the same line between thoroughly tested afamelanotide and unregulated 'melanotans'.^[13][12][17]

Outside trials, melanotan II circulates as an unregulated product bought online, in tanning salons and in gyms, so most adverse-event evidence comes from case reports. The frequent effects mirror the trials: nausea, flushing, yawning, reduced appetite and spontaneous erections. UK regulators have also warned about blood-borne virus transmission through shared needles and about product impurity.^[16][24][5]

The serious reports are rarer but specific. A 39-year-old man developed sympathomimetic toxicity and rhabdomyolysis after an overdose of internet-bought MT-II — identity confirmed by mass spectrometry — and spent three days in intensive care. A renal infarction was judged most likely attributable to MT-II. Ischaemic priapism has followed melanotan use, in one MT-II case needing surgical decompression and in another leaving erectile function unrecovered four weeks later. Posterior reversible encephalopathy syndrome (PRES) has also been reported.^{[23][24][25][26][27][15]}

Pigment changes go beyond a tan. Reports describe eruptive new moles and darkening of existing ones within 24 hours of a single MT-II administration, transverse bands of pigment in the nails with melanotan use, and pigmentation of the gums and cheeks, with the gum changes still visible three months after one user stopped.^[20][21][22]

The honest answer is that nobody knows. A 2017 dermatology review counted four case reports of melanoma emerging from existing moles during or shortly after melanotan use, alongside a larger set of reports of changing and newly appearing, sometimes dysplastic, moles — and concluded that conclusive evidence linking the two is lacking.^[17]

Individual cases show why the question is hard. A 20-year-old woman with fair, type II skin was diagnosed with melanoma three months after a three- to four-week course of MT-II self-injections combined with sunbed tanning; the peptide and the UV exposure cannot be separated. In a man with previous melanoma and dysplastic naevi, a self-administered α-MSH analogue produced crops of new atypical moles that faded after he stopped — evidence that these peptides can drive proliferation of susceptible melanocytes.^[18][19]

The counter-hypothesis — that a melanin tan from these peptides might protect against melanoma — remains unproven. Dermatologists add a practical problem: rapidly darkening moles in unexpectedly tanned patients complicate the clinical assessment of pigmented lesions.^[19][16]

No. Melanotan II has never been authorised as a medicine. EMA's published medicines data, checked on 22 September 2026, contain no product with melanotan II — afamelanotide does appear, as Scenesse — and case reports from 2014 to 2026 consistently describe MT-II as unlicensed.^[14][22][18]

In the United States, the FDA assessed melanotan II when it was nominated as a bulk substance for pharmacy compounding and placed it in category 2 — substances that may present significant safety risks — before the nomination was withdrawn. The agency's summary cites a potential immunogenicity risk from aggregation or peptide-related impurities, and published case reports of melanoma, PRES, sympathomimetic toxidrome and priapism.^[15]

Its regulated relatives are separate molecules with single-indication approvals of their own: afamelanotide for erythropoietic protoporphyria in the EU (2014) and bremelanotide for hypoactive sexual desire disorder in premenopausal women in the US (2019).^[13][12]

Peptyds supplies melanotan II strictly for in-vitro laboratory research, where it serves as a potent reference agonist in melanocortin receptor and signalling assays. It is not sold as a tanning product, a sexual-function aid or an appetite suppressant, and nothing on this page is guidance for human use.^[8][10]

The case literature doubles as a quality lesson. When researchers analysed melanotan II vials bought from three online shops using liquid chromatography with UV and tandem mass spectrometry, every vial held only 43–88% of the labelled amount, and vials from two of the shops carried 4.1–5.9% unidentified impurities.^[28]

That is why every Peptyds batch is documented with a certificate of analysis, and why a high-risk compound like MT-II gets the same documentation standard as the rest of the catalogue. Identity and purity have to be demonstrated per batch, not assumed from a label.