Melanotan II: the basics
What is it?
A lab-made, ring-shaped peptide that copies a natural skin-darkening hormone and switches on several related receptors in the skin and brain.
Research paper 1 ↗Research paper 2 ↗Research paper 3 ↗What do people claim it helps with?
A tan without the sun, plus claims about libido, erections and appetite loss. None of these is an approved or proven safe use.
What has research actually shown?
In the 1990s, a three-person study showed skin darkening, and two ten-man studies showed it could trigger erections. It was never developed into a medicine.
Research paper 1 ↗Research paper 2 ↗Research paper 3 ↗Has this been demonstrated in people?
Only tiny, short human studies from the 1990s plus case reports of harm in people who bought it online. There are no modern controlled trials.
Research paper 1 ↗Research paper 2 ↗Research paper 3 ↗What side effects, risks and unknowns should I understand?
In studies, nausea, yawning, sleepiness and unwanted erections were common. Case reports describe new or changing moles, melanoma, priapism (an erection that will not go away), muscle breakdown, kidney damage and a serious brain condition called PRES. FDA also warns about impurities and immune reactions.
FDA safety information 1 ↗Research paper 2 ↗Research paper 3 ↗Is it an approved medicine?
No FDA-approved medicine contains this peptide. Availability online or at gyms does not mean it has been approved or tested for safety.
FDA safety information ↗Approval here means U.S. FDA approval and applies to a particular product, formulation and use. This is a starting overview, not a complete side-effect list. Sources checked 10 October 2026; independent scientific review pending.
How is it used or studied?
Sold online, often as injectable powders labelled "research use". These products are unregulated, and their contents and strength may not match the label.
Different routes and formulations can have different effects. A study of one product does not validate every product with the same peptide name.
A common misunderstanding
Melanotan II is not afamelanotide (the approved Scenesse implant) and not bremelanotide (the approved Vyleesi injection), even though the molecules are related.
What should I ask a clinician?
- What diagnosis or goal are we trying to address, and what established options are available?
- Was the expected benefit shown in people like me, using this exact product?
- How could my medicines, health conditions or pregnancy plans affect the risks?
- What monitoring is needed, and what would tell us the treatment is helping or should be stopped?
What do the research words mean?
- Peptide
- A short chain of amino acids, the building blocks of proteins.
- Preclinical
- Research in cells, tissues or animals before dependable treatment evidence in people.
- Controlled trial
- A study comparing a treatment with another treatment or a placebo to help separate its effects from other explanations.
- Biomarker
- A measurement, such as a hormone level. A change does not necessarily mean someone feels better or lives longer.
Melanotan II Evidence & Clinical Profile
Human Study Limits
Melanotan II has been investigated in clinical contexts. Patient outcomes must be evaluated against study size, design, and control cohorts.
Laboratory & In Vivo Assays
Cellular and animal disease models examine receptor binding affinities and signaling cascades, which require human confirmation.
What is Melanotan II?
Melanotan II (MT-II) is Melanotan II is a small, ring-shaped synthetic peptide that switches on several melanocortin receptors. It was studied in the 1990s in a handful of volunteers and men with erectile dysfunction, then never developed into a medicine. It is sold online, often for "sunless tanning", without FDA approval. FDA lists it among bulk substances that may pose significant safety risks, and published case reports describe melanoma, new or changing moles, priapism, rhabdomyolysis and other serious events in users. Aliases include: MT-II, Melanotan-II, Melanotan 2.
- Sequence (one-letter)
- Ac-Nle-c[DHfRWK]-NH2
- Molecular formula
- C50H69N15O9
- Molecular weight
- 1024.2 g/mol
- CAS Number
- 121062-08-6
- UNII Code
- UPF5CJ93X7
- PubChem CID
- 92432
Identifiers are for the free base; melanotan II acetate carries UNII WYE6CXB7CH.
Identifiers checked against PubChem and FDA's Global Substance Registration System on 13 October 2026. FDA substance record ↗ · PubChem record ↗ See all names and codes in the peptide name index.
Clinical Trials & Human Cohorts
Human research can examine tolerability, symptoms or patient outcomes. The design and comparator determine what each result can establish.
Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study [1]
What was reported
Two of three had measurably darker skin on the face, upper body and buttocks. Spontaneous erections, stretching and yawning, and mild nausea were reported; one had moderate sleepiness and fatigue.
What limits the conclusion
Three people, two weeks, no long-term follow-up. It shows that the peptide can tan human skin, not that it is safe.
Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction [2]
What was reported
Erections developed in 8 of 10 men; rigid erection time averaged 38 minutes vs 3 with placebo.
What limits the conclusion
Ten men, single sessions. Nausea, stretching and yawning, and reduced appetite were more common than with placebo.
Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction [3]
What was reported
Erections followed 12 of 19 melanotan II injections vs 1 of 21 placebo injections, and sexual desire scores were higher.
What limits the conclusion
Ten men. Severe nausea followed 4 of 19 injections.
How the compound may work
Mechanisms describe how Melanotan II may affect biological processes. Laboratory findings and patient outcomes answer different questions.
Non-selective melanocortin agonist
Melanotan II activates several melanocortin receptors rather than one. This explains why it affects skin pigment, sexual function, appetite and possibly blood vessels at the same time. [9]
Skin pigmentation
By acting like alpha-MSH on pigment cells, it increased skin darkness in volunteers. The same stimulation of melanocytes is why dermatologists worry about mole changes. [1]
Erections via the brain
It triggered erections in men with erectile dysfunction, an effect attributed to central melanocortin signalling. Bremelanotide, an approved drug for a specific female sexual-desire disorder, differs from melanotan II only at its tail end (free acid instead of amide, per PubChem). [2]
Areas Being Studied
These research topics reflect active areas of scientific exploration, distinct from unverified commercial marketing claims.
Melanoma and mole changes
Case reports describe new crops of moles, darkening of existing moles and several melanomas in users. A causal link is not proven, but reviewers urge caution, especially in people with many moles or past melanoma. [6]
Priapism
Painful erections lasting hours, needing emergency treatment and in one case surgery, have followed melanotan II injection. [7]
Systemic toxicity
Reports include sympathomimetic toxicity with rhabdomyolysis and kidney injury, a renal infarction, and posterior reversible encephalopathy syndrome (PRES). [10]
Compare the study designs.
| Study | Design / sample | Outcome type | Key limitation |
|---|---|---|---|
| Pilot Phase I in volunteers · 1996 [1] | Single-blind, placebo-controlled, alternating-day pilot study n = 3 |
Clinical endpoint evaluation | Three people, two weeks, no long-term follow-up. It shows that the peptide can tan human skin, not that it is safe. |
| Psychogenic erectile dysfunction · 1998 [2] | Double-blind, placebo-controlled crossover study n = 10 |
Clinical endpoint evaluation | Ten men, single sessions. Nausea, stretching and yawning, and reduced appetite were more common than with placebo. |
| Organic erectile dysfunction · 2000 [3] | Double-blind, placebo-controlled crossover study n = 10 |
Clinical endpoint evaluation | Ten men. Severe nausea followed 4 of 19 injections. |
Regulatory Status & Clinical Safety
Regulatory Classification
United States, checked 11 October 2026: no FDA-approved medicine contains melanotan II. FDA lists it on its page of bulk drug substances that may present significant safety risks in compounding, citing immunogenicity, aggregation and impurity concerns and published case reports of melanoma, posterior reversible encephalopathy syndrome, sympathomimetic toxidrome and priapism. Products sold online as "research peptides" are unregulated and may not contain what the label says. Other national regulators have also warned against unlicensed melanotan products. As a substance with no current approval for human therapeutic use, it falls under WADA category S0 (non-approved substances). [12]
Safety Realities & Impurities
Safety depends on the molecule, formulation, route and evidence. A laboratory purity measurement alone cannot establish safety for human use.
Clinical Trials Registry Records
Official registry records from ClinicalTrials.gov. Study registration does not imply government endorsement or guaranteed efficacy.
WADA & Anti-Doping Regulations
WADA Section S0: Prohibited Substance
The World Anti-Doping Agency (WADA) classifies Melanotan II under Section S0 of the Prohibited List. Prohibited at all times (in- and out-of-competition). Last verified: October 2026.
Research Timeline
-
1996
First human pilot
A three-person pilot study shows tanning plus erections, yawning and nausea. [1]
-
1998
Erectile dysfunction study
A 10-man crossover study reports drug-induced erections. [2]
-
2009
Mole case reports
Dermatology journals report eruptive moles after melanotan injections bought online. [5]
-
2014
Melanoma case report
A 20-year-old woman develops melanoma after self-injecting melanotan II alongside sunbed use. [4]
-
2026
FDA safety-risk listing
FDA's bulk-substances safety page (current as of April 2026) lists melanotan II and its reported serious adverse events. [12]
What Researchers Still Don't Know
Long-term safety profiles
Multi-year observational data in broader heterogeneous cohorts remains uncharacterized.
Optimal dose-response thresholds
Comparative trials optimizing minimal effective exposure versus adverse event rates.
Formulation bioavailability
Differences between oral, subcutaneous, and modified peptide delivery vehicles.
References
Primary sources verified against PubMed / NLM and regulatory databases.
- Pilot Phase I study
- Crossover trial
- Crossover trial
-
Case report
Melanoma associated with the use of melanotan-II ↗ (external website)
-
Case report (letter)
Eruptive melanocytic naevi following melanotan injection ↗ (external website)
- Review
-
Case report
Melanotan Tanning Injection: A Rare Cause of Priapism ↗ (external website)
-
Case report
Melanotan-induced priapism: a hard-earned tan ↗ (external website)
- Case report and review
-
Case report
Melanotan II injection resulting in systemic toxicity and rhabdomyolysis ↗ (external website)
-
Case report (letter)
Melanotan and the posterior reversible encephalopathy syndrome ↗ (external website)
-
FDA safety page
Content current as of 22 April 2026; melanotan II entry checked 11 October 2026.