Melanotan II

Melanotan II is a synthetic peptide that activates melanocortin receptors and has been studied for darkening skin and for effects on sexual function. It is a research chemical — it is not FDA-approved, and the FDA and other health agencies have specifically warned against using unapproved melanotan products. It has not been proven safe or effective for general use. This page is purely educational and is not medical advice; any decision about Melanotan II belongs with a licensed clinician.

Important: Most of what is publicly documented about Melanotan II in everyday use comes from case reports of harm and from regulator warnings, not from large, approved clinical programs. "Research use only" material sold online is not an approved medicine, its purity is not guaranteed, and it is not a substitute for supervised care.

What is Melanotan II?#

Melanotan II (also written MT-II or MT2) is a small, synthetic, cyclic peptide modeled on alpha-melanocyte-stimulating hormone (alpha-MSH), a natural hormone that helps regulate skin pigmentation. It was originally explored in academic research as a tool to stimulate the body's own pigment-producing pathway, with the idea of producing a protective tan with less ultraviolet (UV) exposure.

Unlike its relative melanotan I (afamelanotide), Melanotan II is not an approved medicine. It is sold and used as an unregulated research chemical, frequently as injections or nasal sprays marketed for tanning, appetite suppression, or libido — all uses for which it has not been approved or proven safe.

How does Melanotan II work?#

Melanotan II is a non-selective melanocortin-receptor agonist — it activates several melanocortin (MC) receptor subtypes rather than just one:

• At the MC1 receptor on melanocytes (pigment cells in the skin), it stimulates the production of melanin, which darkens the skin. This is the basis of its "tanning" effect.
• At the MC3 and MC4 receptors in the brain, it influences pathways involved in appetite and sexual arousal, which is why reduced appetite and increased sexual desire and erections have been reported in research.

This broad, non-selective activity is also why Melanotan II produces effects far beyond tanning — and why some of those off-target effects (on the cardiovascular system, blood vessels, and pigmented lesions) are a safety concern.

What is Melanotan II studied for?#

Melanotan II has been investigated in animals and in some small human studies, but it is not an approved treatment for any of the uses below. Much of the human safety information comes from case reports rather than controlled trials.

Notably, development of Melanotan II for sexual dysfunction was discontinued, and a closely related molecule — bremelanotide (PT-141) — was developed instead and later FDA-approved as Vyleesi (2019) for a specific condition in some premenopausal women. Melanotan II itself never completed an approval pathway.

Is Melanotan II legal and FDA-approved?#

Melanotan II is not FDA-approved for any indication. It is an unapproved research chemical. The FDA has issued warnings and warning letters about products containing melanotan, stating there is no evidence they are generally recognized as safe and effective, and advising consumers who are using such products to stop and consult their health care provider.

International regulators echo this. The UK's MHRA, Australia's Therapeutic Goods Administration (TGA), and EU authorities have all warned against tanning products containing melanotan, citing unknown long-term effects and serious documented harms.

It is important not to confuse Melanotan II with two different, approved drugs in the same family: afamelanotide (Scenesse), an FDA-approved melanotan-I-based product for a rare light-sensitivity disorder (erythropoietic protoporphyria), and bremelanotide (Vyleesi), an approved melanocortin agonist derived from melanotan-II chemistry. The fact that related molecules are approved does not make Melanotan II approved, safe, or interchangeable with them. Material sold "for research use only" has not been evaluated by the FDA for safety, purity, or effectiveness.

How is Melanotan II dosed in research?#

There is no validated, approved human dose for Melanotan II, and WikiPeps does not publish dosing protocols or amounts for any peptide. Because it was never developed into an approved medicine, there is no established therapeutic dose, no standard concentration, and no quality assurance on the unregulated material sold online.

Importantly, several of the most serious published harms — including a case of rhabdomyolysis and acute kidney injury — followed real-world self-injection of material obtained over the internet. Dosing decisions are medical decisions. If you are considering anything in this space, that conversation belongs with a licensed clinician who can weigh your individual risks, not with a website or vendor.

How is Melanotan II reconstituted?#

Melanotan II is supplied as a lyophilized (freeze-dried) powder that would be reconstituted with bacteriostatic or sterile water before use in a research setting. The general, education-only steps — inspecting the vial, disinfecting stoppers, adding diluent slowly down the vial wall, swirling gently rather than shaking, and storing the solution refrigerated and protected from light — are the same handling principles that apply to lyophilized peptides generally.

For a complete walk-through of the technique, see our guide at /learn/guides/how-to-reconstitute-a-peptide. Reconstitution information is provided for understanding only; it is not an endorsement of using an unapproved substance, and the specific diluent volume is a product- and clinician-specific question that we do not answer with amounts.

What are the safety considerations?#

Melanotan II's safety profile is a serious concern, ranging from common, predictable effects to rare but severe events documented in the medical literature:

• Common effects: nausea, facial flushing, and appetite suppression are frequently reported. Spontaneous erections have also been reported in men.
• Pigment and mole changes: Melanotan II can darken existing moles and freckles, create new moles, and cause uneven pigmentation. Dermatologists warn this can mask the warning signs of melanoma, making skin cancer harder to detect.
• Skin cancer concern: Multiple case reports describe melanoma diagnosed in melanotan users, sometimes arising in pre-existing moles. A causal link is not proven in controlled studies, but the association is taken seriously.
• Serious, documented events: Published case reports include rhabdomyolysis (severe muscle breakdown) with acute kidney injury after injection, renal infarction, posterior reversible encephalopathy syndrome (PRES) (with seizures, visual disturbance, headache, and confusion), priapism, and cardiovascular effects from sympathetic overstimulation.
• Product-quality risk: Because this is an unregulated research chemical, the actual contents, purity, sterility, and concentration of any given vial cannot be assumed. Contamination and mislabeling are real risks. Injection and nasal-spray use also carry infection risks.
• Unknown long-term effects: There is no long-term human safety data. The effects of repeated, sustained use are simply not established.

Anyone who has used Melanotan II and notices changing moles, new skin lesions, severe muscle pain, dark urine, severe headaches, vision changes, or other concerning symptoms should seek medical care promptly.

The bottom line#

Melanotan II is a synthetic melanocortin agonist that can darken skin and affect appetite and sexual function — but it is an unapproved research chemical, not a proven or regulated medicine. The FDA and international health agencies have warned against it, and the published literature includes serious harms such as rhabdomyolysis, renal infarction, PRES, and melanoma in users, alongside its tendency to change moles in ways that can hide skin cancer.

Related molecules (afamelanotide and bremelanotide) are approved for specific, narrow uses, but that does not make Melanotan II safe, legal as a medicine, or interchangeable with them. This page is education, not medical advice, and WikiPeps does not publish dosing protocols. Any decision about Melanotan II should be made with a licensed clinician who can weigh the documented risks against your individual situation.