Skip to main content
Professor Peptides
FDA Approved 9 views

Melanotan-II

Melanocortin receptor agonist for tanning and appetite suppression

Melanotan-II molecular structure

Overview

Melanotan II is a synthetic cyclic lactam analog of alpha-melanocyte stimulating hormone (α-MSH) that binds to melanocortin receptors, primarily MC1R in skin and MC4R in the brain. The peptide induces melanogenesis, stimulating melanocytes to produce eumelanin and resulting in skin pigmentation (tanning) without UV exposure. Beyond tanning effects, Melanotan II acts on hypothalamic MC4R to suppress appetite and may promote fat loss. Research indicates effects on sexual arousal and erectile function through central nervous system pathways, leading to development of the related compound PT-141 (Bremelanotide). Common side effects include nausea, facial flushing, and fatigue. The peptide requires subcutaneous injection and users typically undergo a loading phase followed by maintenance dosing. Melanotan II is not FDA-approved and carries risks including potential effects on existing moles and unknown long-term safety. It should be distinguished from Melanotan I (Afamelanotide), which is more selective for MC1R and has been approved in some countries for specific photosensitivity disorders.

Last reviewed: 2026-08-18

Identity & Aliases

Also known as

MT-IIMelanotan 2Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2bremelanotide (PT-141) precursor
CAS121062-08-6
PubChem92432

Full composition (formula, molecular weight, sequence) in Quick Facts →

Research Areas

Skin pigmentation / tanning researchErectile dysfunction (investigational)Sexual arousal and desireMelanocortin receptor pharmacology

Available Evidence

Human

Clinical studies of MT-II demonstrated dose-dependent skin tanning in healthy volunteers and initiation of erections in men with psychogenic erectile dysfunction (double-blind, placebo-controlled crossover study). Its metabolite bremelanotide (PT-141) was FDA-approved in 2019 (Vyleesi) for hypoactive sexual desire disorder in premenopausal women; MT-II itself is not FDA-approved.

Animal

Rodent studies show MT-II activates melanocortin receptors (MC1R, MC3R, MC4R, MC5R), driving pigmentation, feeding suppression, and erectile responses.

In Vitro

Binding assays characterize MT-II as a potent non-selective agonist of MC1R, MC3R, MC4R, and MC5R.

Uncertain

Consumer use of unapproved MT-II for 'sunless tanning' is widespread but unregulated; long-term melanoma risk and other safety questions remain unverified, and appetite/sexual claims are based on limited clinical work.

Key Studies & Findings

2 studies
Clinical1998

In a double-blind, placebo-controlled crossover study, the synthetic melanotropic peptide (MT-II) initiated erections in men with psychogenic erectile dysfunction.

Randomized, double-blind, placebo-controlled crossover study (Journal of Urology)
Clinical2019

Bremelanotide (PT-141), derived from MT-II, was approved by the FDA for hypoactive sexual desire disorder in premenopausal women.

FDA approval (Vyleesi)

Benefits & Effects

7 documented

Penile erection in 17/20 men without sexual stimulation

clinicalsexual function

Increased sexual desire

clinicalsexual function

Weight loss and fat reduction

preclinicalbody composition

Tanning/skin pigmentation

clinicaldermatological

Tanning without UV exposure

anecdotalCosmetic
View Source

Erectile function enhancement

anecdotalSexual Health
View Source

Appetite suppression

anecdotalWeight Loss
View Source

Side Effects & Safety

15 reported

Nausea (12.9% severe at 0.025 mg/kg)

moderatecommon

Facial flushing

mildcommon

Yawning

mildcommon

Priapism (case reports)

severerare

Nausea

MildCommon Reversible

Onset: immediate

View Source

Facial flushing

MildCommon Reversible

Onset: immediate

View Source

Melanocytic changes

SevereUncommon

Onset: months

View Source

NOT APPROVED - health warnings

SevereCommon
View Source

Priapism (SERIOUS)

SevereUncommon

Onset: within hours

View Source

Mild-Moderate side effect

Mild-ModerateVery common Reversible

Onset: 15 min - 2 hours

Management: Symptomatic; dose reduction

Dose-dependent

View Source

Mild side effect

MildCommon Reversible

Onset: Shortly after

Management: Supportive care

Dose-dependent

View Source

Severe side effect

SevereRare (case reports) Reversible

Onset: Within 2 hours

Management: ICU; IV fluids; benzodiazepines

Dose-dependent

View Source

Moderate side effect

ModerateCommon

Onset: 1-2 weeks

Management: Dermatologic exam; discontinue

Dose-dependent

View Source

Severe side effect

SevereRare (4 cases documented)

Onset: Variable

Management: Surgical excision; oncologic follow-up

View Source

Moderate side effect

ModerateCommon in males Reversible

Onset: 1-5 hours

Management: Urologic evaluation if >4 hours

Dose-dependent

View Source

Limitations & Open Questions

MT-II is unapproved and carries notable safety concerns: nausea, flushing, darkened moles, spontaneous erections, and unverified long-term melanoma risk. Most use is off-label or underground without medical oversight, and the compound is not standardized or regulated.

Pharmacology

Short-acting cyclic peptide administered by subcutaneous injection. Mechanism: non-selective agonism of melanocortin receptors - MC1R drives melanogenesis (tanning), MC4R contributes to appetite and erectile/sexual pathways; PT-141 (bremelanotide) is its desacetylated metabolite.

Reported Research Dosing

Reported values from research literature and community protocols. Educational reference only — not a dosing recommendation or medical advice.

0.5-1 mg Loading then maintenance

Route: SC
Half-life: ~1 hour

Research Protocols

Initial Loading

Dose
0.25mg
Frequency
Daily
Route
Subcutaneous

Tanning Maintenance

Dose
0.5-1mg
Frequency
2-3x weekly
Route
Subcutaneous

Sexual Enhancement

Dose
0.5-1mg
Frequency
As needed
Route
Subcutaneous

Minimal Side Effects

Dose
0.1-0.25mg
Frequency
Every other day
Route
Subcutaneous

Photoprotection

Dose
0.5mg
Frequency
2x weekly
Route
Subcutaneous

Research protocols are for educational purposes only. Always consult qualified medical professionals.

Frequently Asked Questions

Is Melanotan II FDA-approved?

No. MT-II itself is not approved. Only its metabolite bremelanotide (PT-141, Vyleesi) is FDA-approved, and only for hypoactive sexual desire disorder in premenopausal women.

Why is Melanotan II used for tanning?

It is a potent agonist of MC1R on melanocytes, which stimulates melanogenesis (tanning) without UV exposure - an off-label use for which it is unapproved and unregulated.

Is Melanotan II safe?

Safety is not established. Reported side effects include nausea, flushing, darkening of existing moles, and spontaneous erections; effects on melanoma risk are unverified. It should not be used outside regulated clinical research.

Research Citations

1
Afamelanotide (Scenesse) for Erythropoietic Protoporphyria: Long-term Safety

(2024)

Related Resources

Compare Melanotan-IISide-by-side vs another peptidePeptide Tier ListRanked by research depthBrowse PeptidesBrowse the full peptide database

Quick Facts

Formula

C50H69N15O9

Molecular Weight

1024.0

Sequence

MACPSLACCLLGLLALTSACYIQNCPLGGKRAALDLDMRKCLPCGPGGKGRCFGPSICCADELGCFVGTAEALRCQEENYLPSPCQSGQKPCGSGGRCATAGICCSPDGCRTDPACDPESAFSER

Mechanism

Melanocortin receptor agonist for tanning

Safety Information

ILLEGAL - NOT APPROVED in any jurisdiction. Multiple national health warnings issued. NO SAFE PROTOCOL. Associated with priapism and melanocytic changes.

View All Peptides