Melanotan II
Melanocortin receptor agonist
A synthetic analog of α-MSH studied in melanogenesis research.
Also referenced as: MT-2, Melanotan-2
Overview
Melanotan II is a synthetic cyclic analog of alpha-melanocyte-stimulating hormone (alpha-MSH), developed from melanocortin research at the University of Arizona. It is a distinct, non-selective compound from the linear Melanotan I.
At a glance
What Melanotan II does
Melanotan II (MT-II) is a synthetic cyclic heptapeptide analog of the hormone α-melanocyte-stimulating hormone (α-MSH), engineered at the University of Arizona to resist enzymatic breakdown and act as a potent, long-lasting melanocortin agonist. Its two headline actions are stimulating skin pigmentation (tanning) and increasing sexual arousal/erectile function — both flowing from its activity at melanocortin receptors. Unlike the selective Melanotan I, MT-II is a non-selective agonist that binds MC1R, MC3R, MC4R and MC5R with broadly comparable affinity.
The tanning effect comes from MC1R activation on melanocytes, which raises cyclic AMP and drives melanogenesis — conversion of tyrosine into melanin — producing darker pigmentation without requiring UV exposure. The sexual effects are separate and stem from MC4R activation in the central nervous system (hypothalamus and spinal cord), which modulates the neural circuitry of arousal and erection; this was discovered incidentally when tanning-study volunteers reported spontaneous erections. Because it activates the whole melanocortin family, MT-II also produces off-target effects such as appetite suppression (an MC4R-linked action) and nausea/flushing.
The evidence is a mix of early human self-experimentation, small clinical/pharmacology studies (including erectile-dysfunction research on the related compound bremelanotide/PT-141, an MT-II metabolite), and dermatology survey data on users. MT-II is not FDA-approved for any use; it is sold as a lyophilized 'research peptide' reconstituted for subcutaneous injection. It is an injectable — not a topical — and its systemic, non-selective action is why it produces both pigmentation and sexual/appetite effects at once.
Effects reported in research
- Stimulates melanogenesis via MC1R activation, increasing skin melanin and producing tanning without UV exposure (human self-experimentation and studies).
- Increases sexual arousal and can induce spontaneous erections via central MC4R activation (observed in human volunteers).
- Non-selective melanocortin agonism across MC1R, MC3R, MC4R and MC5R — the basis for its multiple simultaneous effects.
- Suppresses appetite / reduces food intake, an MC4R-linked central action.
- Commonly causes nausea, facial flushing and spontaneous yawning/stretching — acute melanocortin-agonist effects reported by users.
- Can darken existing moles and freckles and cause diffuse hyperpigmentation as a pigmentation side effect (survey/case data).
- Its metabolite pharmacology underlies bremelanotide (PT-141), which is studied and approved for sexual dysfunction — evidence that MC4R agonism drives the sexual effect.
- Delivered by subcutaneous injection (not topical); it is not FDA-approved for any indication.
Effects listed reflect findings reported in the research literature — many in animal or in-vitro models. Listing an effect is not a claim of efficacy or a therapeutic indication in humans.
Mechanism of action
Melanotan II is a cyclic heptapeptide that acts as a non-selective agonist across melanocortin receptors, including MC1R and MC4R. MC1R agonism on melanocytes stimulates melanogenesis and pigmentation, while MC4R agonism in the central nervous system is associated with effects on sexual arousal, which is the pharmacological basis linking it to the MC4R agonist bremelanotide (PT-141). Its cyclic, constrained structure contributes to potency and metabolic stability.
Mechanistic description reflects published research-literature understanding. Much peptide research is preclinical (in-vitro or animal-model); mechanism in humans may differ and is not established for many compounds.
What it's studied for
Research contexts in which Melanotan II appears in the literature. Listing a research area is not a claim of efficacy or a therapeutic indication.
Key characteristics
- Cyclic heptapeptide analog of alpha-MSH, structurally distinct from Melanotan I.
- Non-selective melanocortin agonist acting at both MC1R and MC4R.
- MC4R activity mechanistically links it to bremelanotide (PT-141).
- Not an approved medicine in any jurisdiction.
- Widely studied in receptor pharmacology as a broad-spectrum melanocortin agonist.
Reported research dosing reference only
Educational reference, not dosing guidance. The figures below summarize amounts reported in published research and research-community protocols, provided for educational and research context only. They are not medical advice, not a recommendation, and not instructions for human use. Melanotan II is a research compound.
Widely referenced research-protocol summaries describe Melanotan II in mcg amounts after reconstitution. These are reference figures for research context only, not human dosing guidance.
- Reported loading-phase reference: ~250-500 mcg/day for roughly 7-10 days
- Reported maintenance reference: ~250-500 mcg two to three times weekly
- Some summaries start lower, ~100-250 mcg, and escalate as tolerance is described
Short plasma half-life (~30-60 min) but prolonged pigmentation effect via melanin synthesis; nausea/flushing are commonly noted in the literature.
How it compares
Melanotan II is a cyclic, non-selective melanocortin agonist (MC1R and MC4R), distinguishing it from the linear, more MC1R-focused Melanotan I and from the MC4R-selective PT-141.
Commonly studied alongside
Compounds frequently researched together with Melanotan II in the literature. Cross-referenced for research context — not a usage or combination recommendation.
Handling & Stability
Lyophilized peptides are stored cold, protected from light, and reconstituted only at the time of intended in-vitro work.
- Avoid repeated freeze-thaw cycles
- Verify supplier lot and Certificate of Analysis
- Follow institutional lab-safety protocols
Analytical & COA Concepts
Reputable research suppliers publish a third-party Certificate of Analysis per batch. Key analytical concepts referenced in COAs include:
Category Context
Melanotan II sits in the Cosmetic & Dermal area of the PeptiDex library.
- Entry type: Research compound reference
- Browse the full library →
- Glossary of terms →
Where researchers source Melanotan II
For researchers studying Melanotan II, third-party suppliers such as Practically Natty Peptides offer research-grade material with third-party Certificates of Analysis and US-based shipping. This specific listing is currently marked out of stock — check the supplier site for current availability.
View research-supplier listing →
Outbound link to a third-party research supplier. Inclusion does not constitute endorsement; all editorial content is developed independently.
Frequently asked questions
What is Melanotan II?
Melanotan II (MT-II) is a synthetic cyclic heptapeptide analog of alpha-melanocyte-stimulating hormone (alpha-MSH). It is a non-selective melanocortin receptor agonist studied in models of melanogenesis (pigmentation) and, via MC4R activity, sexual-response pathways. It is not an approved drug.
How does Melanotan II differ from Melanotan I?
Melanotan I (afamelanotide) is a linear 13-amino-acid alpha-MSH analog and is relatively MC1R-focused, while Melanotan II is a smaller cyclic heptapeptide that is broadly non-selective across melanocortin receptors. The broader receptor activity of MT-II is associated with additional effects such as libido changes and nausea seen in its research literature.
What is the reported half-life of Melanotan II?
Reported plasma half-life is short, on the order of roughly 30 minutes to about 1 hour after subcutaneous administration (some sources cite ~33 minutes). Importantly, pigmentation effects persist for days to weeks because melanocytes are stimulated to produce melanin, so the short plasma half-life does not reflect the duration of the observable effect.
What is the peptide sequence of Melanotan II?
The sequence is Ac-Nle-c[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, a cyclic (lactam-bridged) heptapeptide with a molecular weight of approximately 1024 Da. The cyclization and D-Phe substitution increase resistance to peptidase degradation relative to native alpha-MSH.
How is Melanotan II typically supplied and reconstituted?
It is supplied as a lyophilized powder, commonly in 10 mg vials, and reconstituted with bacteriostatic water for research use. Reconstituted solution is generally kept refrigerated, and the powder is stored frozen and protected from light.
Is Melanotan II an approved drug?
No. Melanotan II is not approved by the FDA or comparable regulators for any use and is handled as a research chemical. It should not be confused with afamelanotide (Melanotan I / Scenesse), which is an approved implant for a specific rare condition.
Answers are educational summaries of research-literature context and do not constitute medical advice. See the Research Library, COA guide, and Storage & Handling guide for more.