How does it work?
MT-2 is a non-selective melanocortin agonist. This means it binds to several melanocortin receptors at the same time. Via the MC1R receptor in the skin it stimulates production of the dark pigment eumelanin, which researchers have linked to darker skin. Via the MC4R receptor in the brain, research has investigated effects on appetite and sexual response. Because the substance affects many receptors at once, its side-effect profile is also broad.
Technical mechanism
Cyclic alpha-MSH analogue. Non-selective melanocortin agonist that activates MC1R, MC3R, MC4R and MC5R.
What is being researched?
- Skin pigmentation and tanning (darker skin)
- Erection and sexual desire in men (via MC4R)
- Appetite and food intake (mainly in animal experiments)
- Mapping side effects and safety in uncontrolled use
About the evidence: The evidence base for MT-2 is weak. The clinical studies are very small (often fewer than 20 participants) and partly old, and much of what is known about appetite comes from animal experiments. At the same time, there are several well-documented safety concerns linked to the use of unregulated products, including nausea, darkening of moles, reports of skin cancer (melanoma), prolonged and painful erection (priapism), muscle breakdown (rhabdomyolysis) and renal infarction. The long-term effects have not been mapped. This is research and information content only, not health advice.
Research profile
Studies and sources
The links go to independent research databases (PubMed, PubMed Central, ClinicalTrials.gov). The studies are in English and open in a new tab.
Pigmentation and tanning
Early phase 1 studies investigated skin pigmentation. Studies of MT-2 must be distinguished from studies of Melanotan I, which is also discussed below.
- Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study Clinical (human)PubMed· 1996
In this human study, three healthy men received repeated small injections of Melanotan-II. The researchers observed that the skin became darker on the face, upper body and buttocks. The participants also experienced side effects such as mild nausea, tiredness and drowsiness at the highest dose, as well as stretching, yawning and spontaneous erections. The study showed that the substance produced a tanning effect in humans after only a few low doses. This was an early safety study with very few participants.
- Effects of a superpotent melanotropic peptide in combination with solar UV radiation on tanning of the skin in human volunteers Clinical (human)PubMed· 2004
In these three clinical studies in humans, Melanotan-1 (not Melanotan II) was combined with UV-B light or sunlight. The researchers observed that the skin became more tanned in those who received the substance, and that the tan lasted longer than in those who received light only. Those who received the substance also had fewer sunburn cells in the skin. Side effects were mild, mainly nausea and transient facial flushing. The researchers found no harmful changes in the irradiated skin areas in this limited investigation.
Erection and sexual response (MC4R)
Two small, double-blind studies from around 2000 explored whether MT-2 could trigger erection and increase sexual desire in men. This work laid the foundation for the later medicine bremelanotide (PT-141).
- Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study Clinical (human)PubMed· 1998
In this study of ten men who had erection problems with no known physical cause, the researchers compared Melanotan-II with a dummy treatment (placebo). Eight of ten men who received the substance developed an erection, and the erections lasted longer than with placebo. Transient side effects such as nausea, stretching, yawning and reduced appetite were reported more often with the substance. The study was small and concerned a specific group of patients.
- Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction Clinical (human)PubMed· 2000
In this study of ten men who had erection problems linked to physical risk factors, the researchers compared Melanotan-II with placebo. The men reported an erection after 12 of 19 injections with the substance, compared with only 1 of 21 with placebo. The participants also reported higher sexual desire after the substance. Nausea and stretching/yawning were more common with the substance, and four of nineteen injections caused severe nausea. The study was small.
Appetite and food intake
In animal experiments, MT-2 (MTII) has shown an ability to reduce food intake through the melanocortin system. This has so far been little investigated in humans.
- Inhibitory Effect of the Melanocortin Receptor Agonist Melanotan-II (MTII) on Feeding Depends on Dietary Fat Content and not Obesity in Rats on Free-Choice Diets PreclinicalPubMed· 2015
In this animal study, rats were given different types of feed for four weeks, and the researchers measured how much they ate after receiving the substance Melanotan-II in the brain. Rats on a high-fat diet reduced their food intake more than other rats when given the substance. The effect was related to how much fat the feed contained, not to how overweight the rats were. This is a laboratory experiment in animals and says nothing directly about humans.
Safety and side effects (case reports)
A number of case reports describe serious events linked to the use of unregulated MT-2, including skin cancer, muscle breakdown, renal infarction and prolonged erection. These are individual cases, but they recur in the literature.
- Melanoma associated with the use of melanotan-II Clinical (human)PubMed· 2014
This is a patient history (case report). A 20-year-old woman who had used Melanotan-II for three to four weeks together with sunbeds was diagnosed with skin cancer (melanoma). The authors describe how use of the substance coincided in time with the cancer finding, and warn of possible dangers from an unregistered and little-tested substance. A single patient history cannot prove that the substance caused the cancer, but it describes a possible risk.
- Melanotan-associated melanoma in situ Clinical (human)PubMed· 2012
This is a patient history (case report). The authors describe a case of early skin cancer (melanoma in situ) in a person who had used injectable melanotan substances to get a tan. They point out that such substances are sold on the internet without approval and without documented safety, and that mole changes and melanoma have been reported with use. A single patient history cannot prove causation.
- Melanotan II injection resulting in systemic toxicity and rhabdomyolysis Clinical (human)PubMed· 2012
This is a patient history (case report). A 39-year-old man injected 6 mg of Melanotan-II bought on the internet. The patient stated that the dose was six times a starting dose he had been given. Two hours later he developed severe palpitations, sweating, anxiety, tremors and muscle breakdown (rhabdomyolysis) with impaired kidney function. He was admitted to an intensive care unit and improved after fluid treatment. Analyses confirmed that the substance was Melanotan-II. The case shows that high doses can cause serious poisoning.
- Melanotan II: a possible cause of renal infarction: review of the literature and case report Clinical (human)PubMed· 2020
This article reviews the literature on Melanotan-II and presents a patient history in which the substance probably led to renal infarction, that is, an acute interruption of the blood supply to the kidney. The authors describe how the substance has previously been linked to muscle breakdown and kidney failure, and discuss whether it may cause blood-clot-like effects or be directly toxic to kidney tissue. This is a review combined with a single case, not a large study.
- Melanotan Tanning Injection: A Rare Cause of Priapism Clinical (human)PubMed· 2021
This is a patient history (case report). A man developed a prolonged, painful erection (priapism) with reduced blood supply after injecting Melanotan-II under the skin. Standard treatment with drainage and medication in the penis did not help, and he required surgery. The authors point out that such priapism has only been described a few times before, and that it should be regarded as a possible side effect. A single patient history cannot say how often this happens.