Melanotan II

MT-II, MT-2, melanotan-2, Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2; informally "the Barbie drug"

Longevity & cellular

Awaiting medical reviewEN ES DE FR PT ZH+ Follow for updates

Summary

Class: Synthetic cyclic heptapeptide (7 amino acids) analogue of α-MSH; non-selective melanocortin agonist (MC1R, MC3R, MC4R, MC5R)
Mechanism: Darkens skin through MC1R on pigment cells and, because it also hits brain melanocortin receptors, triggers erections, appetite loss, nausea and yawning
Routes studied: Subcutaneous injection (human pilot studies; community); nasal sprays (community, unregulated; no human data)
Dose range reported: Human pilot studies: 0.01–0.03 mg/kg subcutaneous (tanning), 0.025 mg/kg (erection studies). Community: "loading" 0.25–1 mg/day until the desired colour, then 0.5–1 mg once or twice weekly. No approved dose exists anywhere
Half-life: Not well characterised in humans; short (hours), but the pigment effect builds over weeks and outlasts the drug
Storage: Lyophilised: refrigerate, protect from light. Reconstituted: refrigerate; community practice within ~4 weeks
Regulatory status: Never approved anywhere; subject of explicit warnings from the FDA, MHRA, TGA and several European agencies

Doses are as reported in studies or by the community — never recommendations.

1What it is

Melanotan II is a ring-shaped seven-amino-acid peptide designed at the University of Arizona in the late 1980s as a more potent, more stable cousin of the natural pigment hormone α-MSH (Al-Obeidi 1989). It was intended as a "sunless tanning" drug to reduce skin-cancer risk in fair-skinned people. In the first human pilot study the men tanned — but also reported nausea, yawning, stretching and spontaneous erections (Dorr 1996). The erection effect was spun off into a separate programme that produced PT-141/bremelanotide (profile 42). Melanotan II itself was dropped by its licensees in the early 2000s and has never had a sponsor since.

From about 2008 it re-emerged as an injectable grey-market tanning product, sold labelled "for research" or "not for human consumption", and more recently as nasal sprays promoted on social media. Analyses of seized vials have found variable peptide content and impurities (Breindahl 2015). Everything a user injects is therefore of unknown identity and dose, which is distinct from the pharmacology described below.

2How it's thought to work

MC1R (skin). raises cyclic AMP in melanocytes, increasing eumelanin — the same route as afamelanotide, but Melanotan II also darkens existing moles and can bring out new ones.

MC4R and MC3R (brain). erections and increased sexual motivation (hypothalamic dopamine pathways); reduced food intake — in mice Melanotan II was the tool compound that established MC4R's role in appetite (Fan 1997, Nature).

Brainstem. nausea, yawning and stretching, which appear at tanning doses.

Cardiovascular. melanocortin raise blood pressure modestly, as later quantified for bremelanotide.

Activates MC1R on pigment cells, which pass melanin into surrounding skin cells; it also reaches brain melanocortin receptors, which explains its other effects.Schematic — not to scale

Its lack of receptor selectivity is why its side-effect list is broader than afamelanotide's.

3What the research shows

Skin tanning

In the phase 1 pilot, healthy men given Melanotan II for several days developed measurably darker skin (reflectance measurements) with nausea, stretching, yawning and erections as side effects (Dorr 1996, Life Sci). A follow-up tested it combined with UV exposure (Dorr 2000, Arch Dermatol). Small, open-label, decades old. [2][3]

Erectile dysfunction

Ten men with psychogenic ED received 0.025 mg/kg subcutaneous or placebo in a double-blind crossover; erections developed in most on active drug with nausea and yawning common (Wessells 1998, J Urol). A second crossover in 20 men with organic ED, including after prostate surgery, also showed erectile responses and increased desire (Wessells 2000, Urology). Very small; the line of work continued as bremelanotide. [4][5]

Appetite and body weight

Reduced food intake and weight in rodents via MC4R (Fan 1997). No human weight study; appetite loss is reported by users as a side effect, not a studied effect. [6]

Graded C/—

Female sexual function

Rodent work on melanocortins and female sexual behaviour mostly used bremelanotide. No human study of Melanotan II in women.

Safety case reports

Published reports in users of grey-market Melanotan II include eruptive new moles and darkening of existing ones (Cardones & Grichnik 2009), melanoma arising in or near darkened naevi (Hjuler & Lorentzen 2014 and others — temporal association, causation unproven), rhabdomyolysis with systemic toxicity (Nelson 2012), priapism, renal infarction, posterior reversible encephalopathy syndrome and sympathomimetic-type reactions. These are single cases, but they are the only "long-term" human data that exist. [7][8][9]

4Reported side effects and interactions

Literature-reported

nausea (common and dose-related), facial flushing, yawning and stretching, spontaneous erections, appetite loss, fatigue; hyperpigmentation that can be patchy; darkening and multiplication of moles and freckles. Case reports as above. Regulators also flag infection risk from non-sterile product and shared needles.

Community-reported

nausea (users often inject before sleep or start very low), flushing, loss of appetite, increased libido and erections, darkened moles and freckles that may not fade, uneven tan, stomach cramps, vivid dreams, headache; blood-pressure rises reported by those who measure.

Theoretical. the central concern is melanoma — both from stimulating pigment cells in people with many or atypical moles, and because a changing mole is harder to spot when all moles are darkening. Blood-pressure effects in people with cardiovascular disease. Unknown effects in pregnancy. Everything below applies to a product of unknown purity.

Interactions. none established. Additive erections with PDE5 inhibitors (community); additive blood-pressure rise with stimulants is plausible by mechanism.

Markers researchers commonly monitor

Marker	Why it's watched
Full-skin examination with dermoscopy and photographic mole mapping before and during use	the dominant safety concern.
Blood pressure and heart rate	melanocortin agonists raise pressure transiently.
Creatine kinase and renal function if muscle pain or dark urine occurs	a rhabdomyolysis case has been reported.
Weight and appetite	MC4R effects are systemic, not just skin-deep.
No compound-specific blood markers are established; general baselines (CBC, CMP) otherwise

Free for everyone. Safety information is never behind a paywall.

5Reconstitution and handling

Typically sold as 10 mg vials. with , swirl gently, keep cold and dark. Online dosing talk mixes "mg" and insulin-syringe "units", a frequent source of 10-fold errors; the calculator converts between them.

Open in calculator, pre-loaded →

6Commonly studied alongside

PT-141/bremelanotide (its successor; not combined); Melanotan I (compared); community pairing with sunbed or sun exposure, which multiplies rather than reduces skin-cancer risk.

Informational cross-links. Not stack recommendations.

7Regulatory status by region

Region	Status (checked —)
United States	Not approved. Placed in Category 2 of FDA's bulk drug substances list for compounding (2023), so pharmacies may not compound it; FDA has warned consumers against injectable tanning products
European Union	Not authorised; national agencies in Denmark, Norway, Sweden, the Netherlands and others have issued warnings since 2008
United Kingdom	MHRA: unlicensed medicine, illegal to sell or supply; repeated public warnings, including on nasal sprays (2008–2024)
Australia	Schedule 4 (prescription-only) by class; no approved product; TGA warns against purchase and import
South Africa	Not registered †
Sport (WADA)	Not named on the Prohibited List; as a non-approved substance it falls under S0 †

8Open questions

Does Melanotan II increase melanoma risk, or only make surveillance harder? No controlled data exist.
Actual dose–response for tanning vs side effects at community doses.
What is in grey-market vials and nasal sprays.
Whether nasal spray delivery achieves meaningful absorption at all.

9References

1Al-Obeidi F et al. (1989). Potent and prolonged acting cyclic lactam analogues of α-melanotropin: design based on molecular dynamics. J Med Chem. PubMed · DOI
2Dorr RT et al. (1996). Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study. Life Sci. PubMed · DOI
3Dorr RT et al. (2000). Effects of a superpotent melanotropic peptide in combination with solar UV radiation on tanning of the skin in human volunteers. Arch Dermatol. PubMed
4Wessells H et al. (1998). Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study. J Urol. PubMed
5Wessells 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. PubMed · DOI
6Fan W et al. (1997). Role of melanocortinergic neurons in feeding and the agouti obesity syndrome. Nature. PubMed · DOI
7Cardones AR, Grichnik JM (2009). α-Melanocyte-stimulating hormone-induced eruptive nevi. Arch Dermatol. PubMed · DOI
8Nelson ME et al. (2012). Melanotan II injection resulting in systemic toxicity and rhabdomyolysis. Clin Toxicol (Phila). PubMed · DOI
9Hjuler KF, Lorentzen HF (2014). Melanotan-associated melanoma. Br J Dermatol. PubMed · DOI
10Breindahl T et al. (2015). Identification and characterization by LC-UV-MS/MS of melanotan II skin-tanning products sold illegally on the Internet. Drug Test Anal. PubMed · DOI
11FDA (2023). Bulk drug substances for compounding — melanotan II category 2 listing. PubMed

References are being resolved to PubMed/DOI identifiers; links search PubMed for the citation until then.

† Being confirmed by our reviewers against current sources.

10Community

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Self-reported side effects Phase 2

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11Page history

25 Oct 2026Profile published — awaiting medical review

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