Melanotan II
melanotan-2, MT-II, MT-2, melanotan 2, Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2
Melanotan II is a non-selective synthetic melanocortin agonist that darkens skin and produces erections and appetite suppression. It was abandoned in development, has never been approved anywhere, and is sold online for cosmetic tanning. The entire controlled human record consists of three tiny studies from the 1990s totalling 23 participants; the published literature since is dominated by reports of harm, including melanoma, rhabdomyolysis and priapism.
Mechanism
Melanotan II is a cyclic, lactam-bridged truncation of alpha-MSH. Bremelanotide, the approved sexual desire drug, is its C-terminal deamidated analogue - which is why the two share a sexual-response profile. Melanotan II is a broadly non-selective agonist at MC1R, MC3R, MC4R and MC5R.
Each receptor accounts for part of what users experience, and the important point is that they cannot be separated. MC1R agonism on epidermal melanocytes raises cAMP, induces MITF and drives eumelanin synthesis - the tanning effect. MC4R agonism in the hypothalamus produces the erectile response and increased sexual desire, but the same receptor mediates appetite suppression, nausea and increased sympathetic outflow. MC3R and MC5R contribute effects on energy balance and exocrine gland function that are poorly characterised in people. There is no dose that produces pigmentation while leaving central MC4R alone. That is why nausea, flushing, spontaneous erections, loss of appetite and blood pressure changes accompany the tan rather than appearing only at higher doses - they are not side effects of an impurity or of overdosing, they are the drug working as designed.
What the research shows
The entire controlled human record for melanotan II is three small studies, together enrolling 23 people. Dorr and colleagues ran an uncontrolled pilot phase I evaluation in 1996 in three healthy male volunteers, giving escalating subcutaneous doses of 0.01-0.03 mg/kg over two weeks; two of the three showed skin darkening on the face, upper body and buttocks, alongside mild nausea, grade II somnolence and fatigue, and spontaneous erections lasting one to five hours preceded by stretching and yawning. Wessells and colleagues then ran two placebo-controlled double-blind crossover trials, each in ten men - one in psychogenic erectile dysfunction in 1998, one in organic erectile dysfunction in 2000. The 1998 study reported clinically observable erections in 8 of 10 men, with mean tip rigidity above 80% lasting 38.0 minutes on melanotan II versus 3.0 minutes on placebo. The 2000 study reported erections after 12 of 19 active injections versus 1 of 21 placebo doses, and increased self-reported sexual desire, but severe nausea after 4 of 19 injections. All three studies were single-centre, tiny, and short. No phase 3 programme followed; development was abandoned and the compound was never submitted to any regulator. Critically, there has never been a randomised placebo-controlled trial of melanotan II for cosmetic tanning, none with skin-cancer or photoprotection endpoints, and none running long enough to characterise safety over the months or years for which people actually use it.
What has accumulated instead is a case-report literature on harms. Published reports describe melanoma arising in users, eruptive new naevi and rapid darkening or enlargement of existing ones, rhabdomyolysis with sympathomimetic toxicity and renal dysfunction after injection, priapism requiring intervention, and renal infarction. Case reports cannot establish causation and are subject to reporting bias - but there is no counterbalancing body of controlled safety data to weigh them against, and the pattern is consistent with the known pharmacology of a non-selective melanocortin agonist that stimulates melanocyte activity and raises sympathetic tone. A further hazard is rarely discussed: the material is not manufactured to pharmaceutical standards, so identity, purity, endotoxin content and sterility are unverified, and users are typically reconstituting and injecting it themselves.
Evidence assessment
Limited evidence
Human data amount to an uncontrolled pilot phase I study in three subjects and two placebo-controlled crossover trials of ten men each in erectile dysfunction from the late 1990s - 23 people in total. There has never been any controlled trial of melanotan II for the tanning use for which it is actually sold.
Tiers are applied consistently across the library and re-checked when new trials read out. Read the grading method.
Key studies
Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study Limited evidence
Two of three subjects showed skin darkening on the face, upper body and buttocks, with mild nausea, somnolence and fatigue, and spontaneous erections lasting 1-5 hours; the study was uncontrolled and involved only three participants.
Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study Limited evidence
Clinically observable erections occurred in 8 of 10 men; mean duration of tip rigidity above 80% was 38.0 minutes with melanotan II versus 3.0 minutes with placebo (p=0.0045), with transient nausea, yawning, stretching and reduced appetite.
Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction Limited evidence
Erections followed 12 of 19 melanotan II injections versus 1 of 21 placebo doses, with increased self-reported sexual desire; 4 of 19 active injections caused severe nausea. Development was subsequently abandoned in favour of bremelanotide.
Melanotan II injection resulting in systemic toxicity and rhabdomyolysis Limited evidence
Sympathomimetic toxicity with tachycardia, hypertension, mydriasis and diaphoresis, followed by rhabdomyolysis (CPK peak 17,773 IU/L) and renal dysfunction requiring three days of intensive care; mass spectrometry confirmed the injected substance was melanotan II.
Melanoma associated with the use of melanotan-II Limited evidence
Melanoma was confirmed histologically in a 20-year-old woman with Fitzpatrick skin type II who presented with a suspicious gluteal lesion and generalised hyperpigmentation, three months after a 3-4 week course of self-injected melanotan II used alongside sunbed tanning.
Melanotan-associated melanoma Limited evidence
A 42-year-old woman developed suspicious changes in an abdominal melanocytic naevus over three months following subcutaneous melanotan II injections.
Safety
Very common effects include nausea and vomiting (often severe on the first doses), facial flushing, spontaneous and sometimes unwanted erections, yawning and drowsiness, appetite suppression, injection-site pain, and transient rises in blood pressure. Pigmentary effects extend well beyond a tan: darkening of moles, freckles, lips, gums, scars and existing naevi, and the appearance of new ones. Serious events reported in the literature include melanoma, rhabdomyolysis with renal dysfunction, priapism and renal infarction.
The most important thing to say about melanotan II's safety is not a list of risks but the absence of data. There has never been a controlled long-term safety study of any size, and the entire controlled human exposure amounts to 23 people over a few weeks. The compound is supplied by unregulated sellers, self-administered without medical oversight, and its known biology plausibly stimulates melanocyte proliferation in people who are often using it precisely because they have fair skin that tans poorly - the phenotype at highest baseline melanoma risk. It also darkens and changes existing moles, degrading the visual asymmetry, border and colour criteria dermatologists rely on to catch melanoma early. That interaction between the drug's effect and the diagnostic pathway is an under-appreciated harm in its own right.
Regulatory status
| Jurisdiction | Status |
|---|---|
| United Kingdom | Not licensed by the MHRA for any indication. The MHRA has issued repeated public warnings against melanotan I and II injections since 2008 and has taken enforcement action against suppliers, including seizures from beauty and tanning premises. Supply for human use is unlawful. It nonetheless remains readily available online and through some salons. |
| United States | Not FDA-approved for any indication and never submitted for approval. It is not a lawful dietary supplement ingredient, and the FDA has issued warning letters to companies marketing melanotan products. It is sold online under a 'for research use only' designation, which functions as a legal shield permitting sale of an unapproved compound to consumers rather than as any statement about its safety, purity or suitability for human use. |
| WADA (sport) | Not specifically named on the WADA Prohibited List. Athletes should note separately that an unregulated product of unverified composition carries an obvious risk of containing prohibited substances. |
Questions
This cannot be answered with the evidence that exists, and anyone who tells you it definitely does or definitely does not is going beyond the data. Several published case reports describe melanoma in users, and the compound stimulates melanocyte activity, which is a biologically plausible route to harm. But no controlled study has ever measured cancer incidence in users. The honest position is that the risk is unquantified, no one has looked properly, and the people most likely to use it are the fair-skinned phenotype already at highest baseline risk.
Legally, it is what allows an unapproved compound to be sold to consumers without going through drug regulation. It is not a manufacturing standard, not a purity guarantee, and not a statement that the product is suitable for anything. In practice most of what is sold under that label is bought by individuals who inject it, which the sellers know. Treat the phrase as a disclaimer written for a lawyer, not information about the product.
Because it does not distinguish between melanocortin receptors. The MC1 receptor in skin gives the tan; the MC4 receptor in the hypothalamus gives the erections, the appetite suppression and the nausea. They are engaged at the same time by the same molecule. There is no dose at which you get one without the others - this is intrinsic pharmacology, not a contaminant or a dosing error.
Twenty-three, in three studies, all completed by 2000. Three healthy volunteers in an uncontrolled pilot, then two crossover trials of ten men each in erectile dysfunction. None of those studies was about tanning, none lasted more than a few weeks, and none was designed to detect harm. Every claim made for melanotan II as a cosmetic product rests on a human evidence base smaller than a single GP surgery's morning list.
Melanotan I (afamelanotide) is a longer, linear peptide with relative selectivity for MC1R, and it is an approved medicine in Europe and the US for a rare light-sensitivity disorder. Melanotan II is a shorter cyclic peptide that hits MC1R, MC3R, MC4R and MC5R indiscriminately, was abandoned in development, and has never been approved anywhere. The central side effects that dominate melanotan II are much less prominent with melanotan I.