Melanotan II — Research Reference

Melanotan II (MT-II) is a synthetic cyclic heptapeptide analogue of alpha-melanocyte- stimulating hormone (α-MSH), the endogenous melanocortin peptide derived from pro-opiomelanocortin (POMC). It was developed at the University of Arizona in the 1980s–1990s during a research programme investigating synthetic tanning agents. MT-II acts as a non-selective agonist at melanocortin receptors 1 through 5 (MC1R–MC5R) — a broader binding profile than more selective analogues.

Regulatory status: Melanotan II is not approved for human use in any jurisdiction and is not a licensed pharmaceutical. It is classified as an unregulated research compound. Regulatory authorities including the UK MHRA, US FDA, and the Australian TGA have issued safety warnings regarding Melanotan II products.

Quick Reference

Overview

MT-II was developed as part of the same research programme that later produced PT-141 (bremelanotide), which is the only melanocortin receptor agonist to have received FDA approval (for hypoactive sexual desire disorder). MT-II binds to melanocortin receptors non-selectively — this broad binding profile accounts for its multiple reported effects, as well as its more pronounced side effect profile compared to more selective analogues.

Research has investigated Melanotan II for its potential role in:

• Skin pigmentation: MC1R activation stimulates melanocytes to produce eumelanin (brown-black pigment), leading to increased skin pigmentation independent of UV exposure. This was the original focus of the Arizona research programme
• Sexual function: MC4R activation in the central nervous system is proposed to mediate pro-erectile effects in males and arousal effects in both sexes. This mechanism, initially identified with MT-II, led to the development of PT-141 (bremelanotide)
• Appetite suppression: MC4R activation in the hypothalamus is associated with appetite reduction, and rodent studies have reported reduced food intake and body weight following MT-II administration
• Penile erection: Early clinical studies reported spontaneous penile erections as a common effect in male participants, independent of sexual stimulation — which later contributed to understanding melanocortin receptor biology

Important distinction from PT-141: PT-141 (bremelanotide) was developed from Melanotan II specifically to reduce cardiovascular effects observed with MT-II. PT-141 is selective and has undergone full clinical development. MT-II is older, less selective, and has not undergone clinical approval processes.

Reported Protocols

The following information represents commonly reported research ranges in anecdotal research accounts. These are not medical recommendations. No clinically validated protocol exists.

Subcutaneous Protocol

Commonly reported doses range from 0.25 mg to 1 mg per use, typically administered subcutaneously to the abdomen:

• Tanning/pigmentation research: 0.5–1 mg per day or on alternating days, with anecdotal accounts describing a “loading phase” of several days to establish baseline pigmentation, followed by reduced frequency maintenance
• Sexual function research: 0.25–0.5 mg administered 30–60 minutes before anticipated use; anecdotal accounts frequently note starting at lower doses (0.1–0.25 mg) to assess individual response to nausea and flushing

Intranasal Protocol

Intranasal administration is reported as an alternative to subcutaneous injection. Commonly reported intranasal doses are generally higher than subcutaneous doses (typically 1–2 mg) due to lower bioavailability via this route. Anecdotal reports describe nasal spray formulations prepared from reconstituted MT-II.

Reported Effects

The following effects have been reported in research publications and anecdotal accounts. This list reflects the research landscape, not confirmed clinical outcomes.

Skin Tanning and Pigmentation

Clinical and anecdotal research consistently reports increased skin pigmentation following MT-II administration, occurring without UV light exposure. The effect is reported to begin within days of starting administration and to persist for weeks after cessation. Irregular or patchy pigmentation increases have also been reported, including darkening of pre-existing moles — which has raised dermatological safety concerns.

Sexual Effects

Research has reported pro-erectile effects in males (including spontaneous erections not associated with sexual stimulation) and increased sexual arousal in both males and females following MT-II administration. These are proposed to be mediated by central MC4R activation.

Appetite and Body Weight

Rodent research and anecdotal human reports suggest appetite reduction following MT-II use. Nausea — a common side effect — may contribute to this effect in humans independently of any direct appetite-suppressing mechanism.

Reported Side Effects

Reported side effects in research and anecdotal accounts include the following. MT-II has a notably broader and more pronounced side effect profile than more selective melanocortin analogues such as PT-141.

Mole and pigmentation concerns: Multiple reports have described darkening of existing moles and development of new moles following repeated MT-II use. Dermatologists have raised concerns about the potential for MT-II-induced atypical mole changes. This concern is considered more clinically significant with MT-II than with more selective MC1R agonists.

Regulatory warnings: The FDA, UK MHRA, and Australian TGA have issued warnings against the use of Melanotan products due to their unregulated status, uncharacterised safety profiles, and concerns about skin changes.

Storage & Handling

Lyophilized Powder (Unreconstituted)

• Room temperature: Reported stable for 6–12 months in sealed, dark conditions
• Refrigerator (2–8°C): Preferred for extended storage
• Freezer: Acceptable for long-term storage; avoid repeated freeze-thaw cycles

Reconstituted Solution

• Refrigerator (2–8°C): Use within 4 weeks of reconstitution
• Do not freeze a reconstituted solution
• Bacteriostatic water (BAC water) is the standard diluent

Reconstitution

Add bacteriostatic water slowly along the inside wall of the vial. Swirl gently — do not shake. See the Reconstitution Guide for step-by-step instructions.

Frequently Asked Questions

What is the difference between Melanotan I and Melanotan II? Melanotan I (afamelanotide) is a linear α-MSH analogue that has been approved in Europe (as Scenesse) for the treatment of erythropoietic protoporphyria — a rare photodermatosis. It is more selective for MC1R (pigmentation) with a longer half-life. Melanotan II is cyclic, shorter-acting, and non-selective across MC1R–MC5R, producing the wider range of effects (including sexual and appetite effects) attributable to MC4R activity.

How does Melanotan II compare to PT-141 (Bremelanotide)? PT-141 was developed from Melanotan II specifically to isolate sexual function effects while reducing cardiovascular and other off-target effects. PT-141 is FDA-approved for hypoactive sexual desire disorder in premenopausal women (as Vyleesi). It has undergone formal safety and efficacy evaluation. MT-II is older, has a broader receptor profile, more pronounced side effects, and no clinical approval. Researchers interested in melanocortin-based sexual function research typically reference PT-141 as the better-characterised compound.

Is Melanotan II the same as Barbie drug or illegal tanning injections? Reports in popular media have referred to unlicensed tanning injections as “Barbie drug” or similar names. These products typically contain Melanotan I or II. They are unregulated, not quality-controlled, and have been the subject of multiple regulatory warnings due to associated adverse events.

Are there any cancer concerns? Regulatory warnings have noted that MT-II-induced changes to moles (nevi) could in theory mask melanoma or stimulate atypical proliferation. No definitive clinical evidence of MT-II causing melanoma has been published, but the theoretical concern is sufficient for dermatologists and regulators to advise strongly against unsupervised use, particularly in those with a personal or family history of melanoma.

Related Pages

Goals: Libido & Sexual Function · Skin & Hair

Class: Melanocortin Peptides

Comparisons: PT-141 vs Melanotan II

References & Further Reading

• Wessells H, et al. (2000). Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction. Urology, 56(4), 641–646. PubMed →
• Van der Ploeg LHT, et al. (2002). A role for the melanocortin 4 receptor in sexual function. Proceedings of the National Academy of Sciences, 99(17), 11381–11386. PubMed →
• Hadley ME. (2005). Discovery that a melanocortin regulates sexual functions in male and female humans. Peptides, 26(10), 1687–1689. PubMed →