Melanotan II

Melanotan II (MT-II) is a laboratory-made peptide based on alpha-melanocyte-stimulating hormone (alpha-MSH), the hormone that signals skin cells to produce melanin. Chemists at the University of Arizona designed a family of cyclic “lactam-bridged” fragments of alpha-MSH in the late 1980s to make a molecule that was more potent and longer lasting than the natural hormone; one of those compounds became melanotan II ^[1]. The same group had already made a linear analogue, melanotan I, and they described both as candidate tanning agents that might reduce reliance on ultraviolet exposure ^[2].

Melanotan II is seven amino acids long (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2) ^[3]. It is closely related to bremelanotide (PT-141), which was developed from melanotan II and is the only compound in this family approved for a sexual-health indication. Melanotan I, under the name afamelanotide, has been approved as a medicine for a limited number of indications, and it is a separate product from the melanotan sold online ^[6].

Today melanotan II is mainly encountered as an unlicensed injectable or nasal spray sold for tanning, often marketed through social media. It is also sold by research peptide vendors labelled “not for human consumption”.

Melanotan II is a non-selective agonist at several melanocortin receptors. Activation of the MC1 receptor on melanocytes increases production of eumelanin, the darker pigment, which is the basis of the tanning effect seen in early human studies ^[3]. Activation of MC3 and MC4 receptors in the brain and spinal cord is linked to effects on sexual function and appetite; studies from the Arizona group showed that melanotan II triggers erections through brain and spinal pathways rather than acting directly on the penis ^[2].

Because it does not target one receptor, the same dose that darkens skin also produces yawning, nausea, flushing, reduced appetite and spontaneous erections. That lack of selectivity is one reason developers moved on to more targeted compounds.

The first human study of melanotan II was a small single-blind pilot phase 1 study in three healthy men published in 1996. Subcutaneous injections on alternate days over two weeks produced measurable darkening of the face, upper body and buttocks in two of the subjects, confirmed by reflectance measurements a week after dosing ended ^[3]. The same study recorded nausea at most dose levels, a stretching and yawning complex, and spontaneous erections lasting one to five hours.

No larger controlled trials of melanotan II for tanning or skin cancer prevention were published. Later clinical development of tanning peptides in this group focused on melanotan I rather than melanotan II ^[2]. There is therefore no controlled evidence that melanotan II protects against sunburn or skin cancer, and some reviewers have argued the opposite concern: that stimulating pigment cells may change existing moles ^[6].

In a 1998 double-blind, placebo-controlled crossover study, ten men with erectile dysfunction of no known physical cause received melanotan II or placebo. Clinically apparent erections developed in eight of the ten men after melanotan II, and rigidity measured by RigiScan lasted much longer than after placebo (38 versus 3 minutes of tip rigidity above 80%) ^[4]. Nausea, stretching and yawning, and reduced appetite were more common with the peptide.

A follow-up crossover study in ten men with erectile dysfunction and physical risk factors found that melanotan II initiated erections after 12 of 19 injections compared with 1 of 21 placebo doses, and that self-reported sexual desire was higher after the peptide ^[5]. Four of the 19 injections were followed by severe nausea. These results led to the development of bremelanotide, a melanotan II derivative, which was taken forward instead of melanotan II itself ^[2].

All published controlled human data on melanotan II come from a handful of small studies by the University of Arizona group in the 1990s, involving roughly two dozen participants in total ^[3][4][5]. There are no phase 2 dose-finding trials for tanning, no phase 3 trials for any use, and no long-term safety follow-up.

Most of what is now known about melanotan II in people comes from case reports of unsupervised use, where the product’s identity, purity and dose are usually unknown. Those reports are summarised under safety below.

In the 1996 pilot study, subcutaneous doses started at 0.01 mg/kg and were increased in 0.005 mg/kg steps to 0.025 to 0.03 mg/kg; the 0.03 mg/kg dose caused moderate (grade II) sleepiness and fatigue in one of two subjects, and the authors proposed 0.025 mg/kg as the single dose for future studies ^[3]. The two erectile dysfunction studies both used 0.025 mg/kg by subcutaneous injection ^[4][5].

These figures describe what small, supervised research studies used. They are not a recommended or established dose, no dose has been shown to be safe for repeated cosmetic use, and the amount of peptide in unlicensed products has been found to vary. Figures quoted in online “protocols” do not come from controlled trials.

In the early studies, the most common effects were nausea, flushing, yawning and stretching, reduced appetite, sleepiness and spontaneous erections ^[3][4][5]. These occurred at the doses used in supervised settings, in small numbers of healthy volunteers.

Case reports from unsupervised use raise more serious concerns. Dermatologists have described new moles appearing, existing moles darkening or changing, and atypical (dysplastic) naevi after melanotan injections; a 2009 report in the BMJ linked mole changes to an unlicensed “sun tan jab” ^[7]. A 2017 review found four published cases of melanoma arising in existing moles during or shortly after melanotan use, while noting that conclusive evidence of cause and effect is lacking ^[6]. One such case was a 20-year-old woman who used melanotan II alongside sunbeds for three to four weeks and was diagnosed with melanoma three months later ^[8]. A systematic review of eruptive naevi of 179 published patients found that immunosuppressants, chemotherapy or melanotan were the suspected trigger in 41% of cases, and that 16% of all cases had at least one dysplastic naevus, although the data did not allow the risk of malignant change to be estimated ^[9].

Other reported harms include prolonged, painful erections (ischaemic priapism) requiring surgery ^[10] and a renal infarction in which melanotan II was considered the most likely cause ^[11]. The US Food and Drug Administration’s compounding review lists published case reports of melanoma, posterior reversible encephalopathy syndrome, sympathomimetic toxidrome and priapism among its concerns ^[15].

Case reports cannot show how often these effects occur or prove that melanotan II caused them; many users also used sunbeds. But because the product is unlicensed, users cannot be sure what a vial or spray contains, and regulators have made the same point ^[12]. Injecting any unlicensed product also carries infection risks from non-sterile preparation or shared equipment. Anyone who has noticed a new or changing mole should have it checked by a doctor.

Melanotan II has never been authorised as a medicine in any country. In the UK, the Medicines and Healthcare products Regulatory Agency (MHRA) says injectable melanotan II products are classed as medicines, that selling, supplying or advertising unauthorised medicines is not permitted, and that it has repeatedly acted to remove melanotan products from the market for over 10 years. Its advice is that anyone who has used melanotan II injections or nasal sprays should stop immediately and report side effects through the Yellow Card scheme. Nasal sprays are treated as medicines only if sold with medical claims ^[12]. See UK legal status.

In Australia, the Therapeutic Goods Administration (TGA) states that melanotan II is a prescription-only (Schedule 4) substance, that no product containing it is on the Australian Register of Therapeutic Goods, and that supplying tanning products containing it without a prescription is illegal ^[13]. See Australian legal status.

In the US, the FDA’s position in enforcement proceedings has been that melanotan II is an unapproved new drug that cannot lawfully be sold without an approved application; it sent a warning letter to one seller in 2007 ^[14]. The FDA’s list of bulk substances reviewed for pharmacy compounding (as of April 2026) records melanotan II among substances previously placed in its “significant safety risks” category whose nominations were withdrawn ^[15]. See US legal status.

Melanotan II is usually sold as a freeze-dried (lyophilised) powder. Like most research peptides, the powder is generally kept cold, dry and away from light, and is less stable once mixed with liquid. Our peptide storage guide covers general handling; there is no manufacturer’s licensed product information for melanotan II because no licensed product exists.

Because no licensed product exists, every melanotan II product on the market is unregulated, and dose consistency cannot be assumed. If you are researching suppliers, you can compare prices, learn how to read a COA, see our list of third-party tested suppliers, and read how to spot a fake peptide supplier.