RESEARCH PROFILE
MELANOTAN II
Synthetic Melanocortin Analog • Pigmentation & Melanocortin Research
Melanotan II, commonly abbreviated MT-II or MT-2, is a synthetic cyclic melanocortin peptide developed from research involving alpha-melanocyte-stimulating hormone, or α-MSH.
Research has examined its effects on pigmentation, melanocortin signaling, sexual response, and appetite. Small early human studies demonstrated measurable biological activity, but Melanotan II was never developed into an FDA-approved drug.
HUMAN EARLY-PHASE RESEARCH • NONSELECTIVE MELANOCORTIN AGONIST • NOT FDA APPROVED
MELANOTAN II AT A GLANCE
Other Names
Melanotan 2 • MT-II • MT-2
Compound Type
Synthetic cyclic melanocortin peptide
Origin
α-MSH analog
Primary Receptor Activity
MC1R • MC3R • MC4R • MC5R
Primary Research Focus
Pigmentation • Sexual response • Melanocortin signaling • Appetite
Human Evidence
Small early Phase 1 and Phase 2 studies
Regulatory Status
Not FDA approved
IMPORTANT DISTINCTION
Melanotan II activates multiple melanocortin receptor subtypes.
That broad receptor activity helps explain why a single compound can influence several seemingly unrelated processes:
Skin pigmentation
Sexual response
Appetite
Autonomic effects
It also contributes to its side-effect profile.
Later melanocortin drugs were designed to be more selective.
Afamelanotide primarily targets pigmentation pathways and has an FDA-approved indication.
Bremelanotide, or PT-141, primarily targets central sexual-response pathways and also has an FDA-approved indication.
Melanotan II itself does not have an FDA-approved indication.
WHAT IS MELANOTAN II?
Melanotan II is a synthetic cyclic peptide developed during research into alpha-melanocyte-stimulating hormone, or α-MSH.
α-MSH is a naturally occurring hormone involved in melanocortin signaling.
Researchers at the University of Arizona developed melanocortin analogs during the late 1980s and 1990s while investigating ways to stimulate pigmentation.
Melanotan II was designed to be:
More potent than natural α-MSH
More resistant to enzymatic degradation
Longer acting than the native hormone
WHY WAS MELANOTAN II STUDIED?
Initial research focused primarily on skin pigmentation.
During early clinical research, investigators also observed effects involving:
Spontaneous erections
Sexual arousal
Appetite
Nausea
Flushing
These observations helped drive later development of more selective melanocortin compounds.
MELANOTAN II & PT-141
Bremelanotide, commonly known as PT-141, emerged from the same broader melanocortin research lineage.
The compounds are related but are not interchangeable.
PT-141 was developed toward central sexual-response signaling and ultimately became an FDA-approved drug for a specific indication.
Melanotan II remained an unapproved research compound.
MECHANISM OF ACTION
Melanotan II acts as a nonselective melanocortin receptor agonist.
Its effects vary according to which receptor subtype is activated.
MC1R — PIGMENTATION
MC1R is expressed on melanocytes, the cells responsible for producing melanin.
Activation of MC1R stimulates melanogenesis, increasing production of melanin.
Melanin is the pigment responsible for much of the coloration of:
Skin
Hair
Eyes
This pathway accounts for the tanning and pigmentation effects observed in human studies.
MC3R & MC4R — SEXUAL SIGNALING
MC3R and particularly MC4R participate in central nervous-system pathways involved in sexual behavior and arousal.
Activation of these pathways is associated with the spontaneous erections and sexual-response effects observed during early Melanotan II trials.
This is primarily a central nervous-system effect, not simply an increase in genital blood flow.
MC4R — APPETITE
MC4R also plays an important role in appetite and energy-balance signaling.
Activation of this pathway provides a biological explanation for appetite suppression reported with Melanotan II.
MC5R — SECONDARY ACTIVITY
Melanotan II also activates MC5R.
Your Project source describes this receptor as being expressed predominantly in glandular tissues, with its contribution to the overall Melanotan II effect profile less clearly defined.
NONSELECTIVE RECEPTOR ACTIVITY
The key mechanistic characteristic of Melanotan II is its lack of receptor selectivity.
It does not activate only the pigmentation pathway.
It simultaneously affects several melanocortin receptors.
That helps explain both its diverse biological effects and its comparatively broad adverse-effect profile.
IMPORTANT MECHANISM LIMITATION
Receptor activation demonstrates biological plausibility.
It does not establish that Melanotan II is a safe or appropriate method of tanning, appetite modification, sexual enhancement, or any other medical use.
WHAT THE RESEARCH SHOWS
EARLY HUMAN PIGMENTATION RESEARCH
Melanotan II has been studied directly in humans.
Your Project profile identifies early Phase 1 research by Dorr and colleagues involving healthy volunteers.
The study demonstrated measurable increases in pigmentation.
However, nausea and spontaneous erections were also prominent adverse effects.
PSYCHOGENIC ERECTILE-DYSFUNCTION RESEARCH
A placebo-controlled Phase 2 study by Wessells and colleagues investigated Melanotan II in men with psychogenic erectile dysfunction.
The study reported erectile responses in a substantial proportion of treated participants.
This established human pharmacologic activity but did not lead to an approved Melanotan II drug.
ORGANIC ERECTILE-DYSFUNCTION RESEARCH
Additional Phase 2 research investigated men with organic erectile dysfunction.
The Project source reports improved erectile response and rigidity time compared with placebo.
MIXED ERECTILE-DYSFUNCTION ANALYSIS
Combined research involving men with different forms of erectile dysfunction reported:
Increased sexual desire
More spontaneous erections
Improved erectile-response measures
Nausea remained a significant adverse effect.
UV & PIGMENTATION RESEARCH
A 2004 human study evaluated Melanotan II in combination with UV exposure.
The combination produced greater tanning than UV exposure alone.
This demonstrates pharmacologic pigmentation activity.
It does not establish Melanotan II as a safe tanning intervention.
PRECLINICAL SEXUAL-SIGNALING RESEARCH
Animal studies have examined melanocortin signaling through MC4R and downstream pathways associated with sexual behavior.
These studies helped clarify the central mechanism underlying the sexual-response findings observed in humans.
THE EVIDENCE IN CONTEXT
The Project source characterizes the human evidence as:
Small
Early phase
Primarily conducted during the 1990s and early 2000s
Generally involving roughly 20 to 100 participants
The studies demonstrate that Melanotan II has real biological effects in humans.
They do not provide the type of extensive efficacy and long-term safety evidence expected for an approved pharmaceutical.
IMPORTANT EVIDENCE LIMITATION
The evidence supports measurable effects on:
Pigmentation
Sexual response
But it does not establish Melanotan II as an approved or clinically validated treatment for:
Tanning
Erectile dysfunction
Low libido
Weight loss
Appetite control
Photoprotection
Development ultimately moved toward more selective compounds rather than approval of Melanotan II itself.
SAFETY & RESEARCH CONSIDERATIONS
Melanotan II's broad melanocortin-receptor activity produces a wider adverse-effect profile than more selective melanocortin compounds.
NAUSEA
Nausea is one of the most consistently reported adverse effects.
Your Project profile describes nausea as a major dose-limiting effect in early human research.
FLUSHING
Flushing can occur, including sensations of:
Warmth
Redness of the face or chest
Transient skin flushing
APPETITE CHANGES
Reduced appetite has been reported and is biologically consistent with MC4R activation.
FATIGUE & YAWNING
Community and research observations include:
Fatigue
Sleepiness
Yawning
SPONTANEOUS ERECTIONS
Early clinical studies reported spontaneous erections and increased sexual response.
This reflects central melanocortin signaling rather than the peripheral vascular mechanism associated with PDE5 inhibitors.
PRIAPISM
Case reports describe priapism, a prolonged and potentially painful erection.
Priapism is a medical emergency because prolonged erection can cause permanent tissue injury.
MOLE & FRECKLE DARKENING
Melanotan II can increase pigmentation of:
Existing moles
Freckles
Other pigmented skin lesions
New pigmented lesions have also been reported.
MELANOMA CONCERN
Your Project source cites case reports describing melanoma diagnoses or rapidly changing pigmented lesions associated temporally with Melanotan II exposure.
These reports do not prove that Melanotan II causes melanoma.
However, they create a meaningful safety concern because the compound directly stimulates melanocytic pigmentation.
Changes in a mole involving:
Shape
Color
Size
Border
Bleeding
warrant prompt dermatologic evaluation.
RHABDOMYOLYSIS
Your Project profile also cites a case report involving systemic toxicity and rhabdomyolysis following Melanotan II injection.
Rhabdomyolysis involves breakdown of skeletal muscle and can result in serious complications including kidney injury.
CARDIOVASCULAR EFFECTS
Flushing and blood-pressure changes have been reported.
People with significant cardiovascular disease or uncontrolled blood pressure represent an area of particular concern.
PREGNANCY & BREASTFEEDING
There are no adequate human safety data establishing use during pregnancy or breastfeeding.
REGULATORY CONTEXT
MELANOTAN II IS NOT FDA APPROVED
Melanotan II is not FDA approved for any therapeutic or cosmetic indication in the United States.
No company has obtained FDA approval for a Melanotan II drug product.
NOT AN APPROVED TANNING DRUG
Melanotan II is not an FDA-approved tanning medication.
Products marketed as:
Tanning injections
Tanning nasal sprays
Melanotan kits
should not be interpreted as approved pharmaceutical products.
NOT AN APPROVED DIETARY SUPPLEMENT
Your Project source states that Melanotan II is not a lawful conventional dietary supplement merely because it is sold online or labeled as a peptide.
INTERNATIONAL STATUS
The Project profile states that, as of its source date, Melanotan II was not approved for therapeutic use by:
FDA — United States
EMA — European Union
MHRA — United Kingdom
TGA — Australia
The source also describes human-use sales restrictions or regulatory warnings in several jurisdictions.
RESEARCH-USE LABELING
Melanotan II is frequently sold with language such as:
“For research purposes only”
or
“Not for human consumption.”
Such labeling does not establish:
Product quality
Safety
Effectiveness
Sterility
FDA approval
APPROVED MELANOCORTIN DRUGS
Two related but distinct melanocortin drugs illustrate why the distinction matters.
Afamelanotide is FDA approved as Scenesse for a specific indication involving erythropoietic protoporphyria.
Bremelanotide is FDA approved as Vyleesi for a specific female sexual-desire indication.
Melanotan II itself remains unapproved.
IMPORTANT REGULATORY DISTINCTION
Melanocortin activity ≠ FDA approval
Research-use sale ≠ approved human use
Pigmentation effect ≠ approved tanning therapy
Human Phase 1 or Phase 2 research ≠ approved drug
Approval of afamelanotide or bremelanotide ≠ approval of Melanotan II
ANALYTICAL DOCUMENTATION
Croix maintains available third party analytical documentation only for specific samples and lots that can be matched to corresponding laboratory reports.
LOT SPECIFIC ANALYTICAL DOCUMENTATION
Analytical documentation is displayed only when Croix has a corresponding laboratory report that can be matched to the specific product and lot.
No matching Melanotan II COA is currently displayed.
IMPORTANT COA LIMITATION
When analytical documentation becomes available, results should apply only to the specific sample identified in the corresponding laboratory report.
A Certificate of Analysis for one sample does not establish the composition, purity, sterility, safety, efficacy, or characteristics of another sample, lot, batch, or product.
Croix requires the product, strength, lot or batch, sample ID, laboratory, and report date to be matched before analytical documentation is represented as supporting a product.
A passing COA does not establish FDA approval, clinical efficacy, medical suitability, or the characteristics of unrelated lots.
SELECTED RESEARCH & REFERENCES
Dorr RT, Lines R, Levine N, et al.
Evaluation of Melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study.
Life Sciences. 1996.
Early human Phase 1 pigmentation and safety research.
Wessells H, Fuciarelli K, Hansen J, et al.
Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction.
Journal of Urology. 1998.
Human Phase 2 erectile-response research.
Wessells H, Gralnek D, Dorr R, et al.
Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction.
Urology. 2000.
Human erectile-function research.
Wessells H, Levine N, Hadley ME, et al.
Melanocortin receptor agonists, penile erection, and sexual motivation: human studies with Melanotan II.
International Journal of Impotence Research. 2000.
Human melanocortin sexual-response research.
Dorr RT, Ertl GA, Levine N, et al.
Effects of a superpotent melanotropic peptide in combination with solar UV radiation on tanning of the skin in human volunteers.
Archives of Dermatology. 2004.
Human pigmentation and UV research.
Nelson ME, Bryant SM, Aks SE.
Melanotan II injection resulting in systemic toxicity and rhabdomyolysis.
Clinical Toxicology. 2012.
Case report describing serious systemic toxicity.
Hjuler KF, Lorentzen HF.
Melanoma associated with the use of melanotan-II.
Dermatology. 2014.
Dermatologic case report.
Schulze F, Erdmann H, Hardkop LH, et al.
Research describing eruptive nevi and darkening of pre-existing nevi following Melanotan II exposure.
European Journal of Dermatology. 2014.
Pigmented-lesion safety literature.
Mallory CW, Lopategui DM, Gordon BH.
Melanotan tanning injection: a rare cause of priapism.
Sexual Medicine. 2021.
Case report involving prolonged erection.
Hadley ME, Dorr RT.
Melanocortin peptide therapeutics: historical milestones, clinical studies and commercialization.
Peptides. 2006.
Historical and pharmacologic overview of melanocortin peptide development.
EVIDENCE NOTE
Melanotan II has direct human evidence demonstrating pharmacologic effects on pigmentation and sexual response.
However, the studies were generally small, early-phase investigations and did not lead to regulatory approval.
Safety concerns, broad receptor activity, and development of more selective melanocortin compounds are important parts of the scientific context.
RESEARCH & EDUCATIONAL INFORMATION
This profile is provided for research and educational reference. It does not constitute individualized medical advice or establish Melanotan II as safe or effective for personal use.
Melanotan II is a synthetic nonselective melanocortin receptor agonist studied in relation to pigmentation, sexual response, appetite, and melanocortin signaling.
Small early human studies demonstrated measurable pigmentation and sexual-response effects, but the compound did not progress to an approved pharmaceutical product.
Melanotan II is not FDA approved for any therapeutic or cosmetic indication.
FDA approval of related melanocortin drugs such as afamelanotide or bremelanotide should not be interpreted as approval of Melanotan II.
Case reports involving changing pigmented lesions, melanoma diagnoses, priapism, and systemic toxicity do not by themselves establish causation or incidence, but they represent meaningful safety signals that should not be minimized.
Analytical documentation presented by Croix applies only to the specific samples and lots identified in corresponding laboratory reports.