An unapproved ring-shaped alpha-MSH analog that darkens skin and causes erections; tested in a few small 1990s studies, never approved.
Also called Melanotan II, MT-II, MT2, Ac-Nle4-c[Asp5, D-Phe7, Lys10]-alpha-MSH(4-10)-NH2, Barbie drug, Tanning injection
Melanotan-2 is a 7-amino-acid ring-shaped peptide built at the University of Arizona in 1989 as a shorter, tougher copy of alpha-MSH, the hormone that darkens skin. Unlike melanotan-1, it switches on several melanocortin receptors at once: MC1R on pigment cells, which tans the skin, and MC3R and MC4R in the brain, which cut appetite and trigger erections and sexual arousal.
The human data are thin. A 3-man pilot in 1996 found it tanned the face and upper body after 5 low doses, and the men also had spontaneous erections, bouts of yawning and stretching, and mild nausea. Two 10-man placebo-controlled crossover studies in 1998 and 2000 then tested it for erectile dysfunction: erections with tip rigidity over 80% lasted 38 to 45 minutes on the drug versus 2 to 3 minutes on placebo, but some men had severe nausea. Development moved to bremelanotide (PT-141), a close relative of MT-II that became the approved drug Vyleesi. Melanotan-2 itself was never approved anywhere.
Today it is sold online as a tanning injection or nasal spray. Dermatologists have published case reports of new and darkening moles, several melanomas, priapism, rhabdomyolysis and a kidney infarction in people using these products. None of those reports proves the drug caused the problem, but no one has ever studied the long-term safety of repeated use, and the vials are unregulated.
What it binds to, and what happens inside the body after that, step by step.
MT-II is a non-selective agonist at melanocortin receptors MC1R, MC3R, MC4R and MC5R. At MC1R on melanocytes it raises cAMP and eumelanin production, darkening the skin. It crosses into the brain, where MC4R activation in the hypothalamus and spinal pathways triggers erections, sexual arousal, yawning and reduced appetite. That receptor spread is why its side effects are broader than afamelanotide's.
Human results and animal results are kept apart below. A result in rats tells you a mechanism is plausible. It does not tell you what happens in a person.
Humans: two 10-man placebo-controlled crossover trials show it reliably triggers erections, and a 3-man pilot showed skin darkening after a few low doses. That is the entire controlled human dataset, all from one Arizona group in 1996 to 2000, all short-term. Everything else in humans is case reports of harm in people using unregulated products. Appetite and weight effects come from rodent studies only.
10 men with psychogenic erectile dysfunction, double-blind placebo crossover
8 of 10 men had erections; tip rigidity over 80% lasted a mean 38.0 minutes on MT-II vs 3.0 minutes on placebo (P=0.0045).
Read the study10 men with erectile dysfunction and organic risk factors, double-blind placebo crossover
Erections followed 12 of 19 MT-II injections vs 1 of 21 placebo doses; 4 of 19 injections caused severe nausea.
Read the study3 healthy men, single-blind alternating-day placebo design
Two of three men had measurable darkening of the face, upper body and buttocks a week after dosing ended; spontaneous erections came and went for 1 to 5 hours after doses, and mild nausea occurred at most dose levels.
Read the studyOne 39-year-old man who injected 6 mg of internet-bought MT-II
He developed racing heart, agitation and muscle breakdown with CK peaking at 17,773 IU/L and temporary kidney injury; lab testing confirmed the product was MT-II.
Read the studyOne 20-year-old woman with fair skin who used MT-II with sunbeds
A melanoma was diagnosed on the buttock 3 months after a 3 to 4 week course of self-injected MT-II combined with sunbed use.
Read the studyNo preclinical studies are listed as key studies here. The human data above carries the evidence.
These are questions the published research has not answered.
No product containing Melanotan-2 is approved as a medicine by the FDA.
No regulator has approved melanotan-2 for any use. Bremelanotide (PT-141, Vyleesi), its close chemical relative, is the approved drug in this family. Melanotan-2 is not named on the WADA Prohibited List, but WADA's S0 section bans any pharmacological substance with no current approval for human therapeutic use, so athletes should treat it as prohibited. Several national regulators and skin-cancer bodies have issued public warnings about tanning injections sold online.
No human half-life has been published for Melanotan-2, so we do not draw a clearance curve. Half-lives quoted online for it are usually estimates from animal data.
This table records the doses that trials and approved labels used, with the source for each row. It is a record of research, not a recommendation, and it is open to free members.
Which symptoms are expected and which mean stop and get help: side effects and red flags.
Tap a claim to see what the studies found.
MT-II darkens skin without UV in small studies, but no study has shown it protects against sunburn, skin aging or cancer. Most users combine it with sunbeds, and that combination appears in most of the melanoma case reports.
There are case reports of melanoma and fast-changing moles in users, and FDA cited melanoma when restricting compounding. Case reports cannot prove cause, and no study has measured risk. The honest answer is that a real risk has not been ruled out.
Two small placebo-controlled trials in men showed it triggers erections and raised self-rated sexual desire. Its relative bremelanotide is approved for low desire in premenopausal women. Neither fact means MT-II is safe for routine use.
Reduced appetite was reported as a side effect, and rodent studies show MC4R activation cuts food intake, but no human study has measured weight change.
No study has tested nasal MT-II for absorption, dose or safety. One 2025 case report raised oral mucosal melanoma in a nasal spray user, without proof of cause.
They are close relatives: bremelanotide is MT-II with a free acid instead of an amide at the C-terminus. Bremelanotide went through full Phase 3 trials and FDA approval; MT-II never did.
These pairings come up often. Almost none have been tested together in a trial, and the evidence note on each says so plainly.
Users combine injections with sunbeds or sun exposure to speed up the tan, since MT-II amplifies the pigment response to UV.
EvidenceNo study has tested MT-II with sunbeds. Most published melanoma and atypical mole case reports involve exactly this combination, and sunbeds alone raise melanoma risk.
Discussed online for combined tanning and libido effects.
EvidenceNever studied. Both act on the same receptors, so nausea, blood pressure effects and prolonged erections would be expected to add up.
No approved product exists, so there is no labeled storage. Published stability data for research-grade MT-II powder are not available.
No published stability data exist for reconstituted MT-II.
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