Melanotan II

Melanotan II (mt-II) is a synthetic peptide known as 'the tanning peptide': it mimics the natural hormone alpha-MSH and darkens the skin by boosting its pigment, eumelanin. It was originally developed as a photoprotective tanning agent and is the parent compound behind the FDA-approved drug bremelanotide (Vyleesi), though mt-II itself was never approved as a medicine. It is illegal to market, sell, or buy for human use in the US, and Australia has banned it outright. Doctors have reported new and changing moles, including melanoma, in people who used it; these are individual case reports rather than proof it caused them, but the biology makes it plausible. It's available only as an unregulated research peptide.

Melanotan II was first studied for skin tanning and, unexpectedly, erectile effects — an observation that redirected its development; a later double-blind crossover trial reported clinically apparent erections in 8 of 10 men treated. Beyond that, multiple case reports describe darkening of moles, new moles, and melanoma in users — including a 2026 report of five simultaneous early melanomas in one person — plus rhabdomyolysis, renal infarction, and priapism after unregulated use. That evidence is case-report level rather than proof of cause, but the mechanism is biologically plausible. No large trials support the uses people pursue.

Not FDA-approved for any indication. The original development program (University of Arizona / Competitive Technologies / Palatin Technologies) was discontinued in 2000 in favor of bremelanotide development; melanotan II itself never advanced to NDA submission. Illegal to market, sell, or purchase for human consumption in the United States — the FDA has issued multiple warning letters to companies marketing mt-II as a "tanning injection" and has pursued border seizures and website takedowns. Restricted/banned for human use in the UK (MHRA), Australia (TGA), New Zealand, and several other regulated markets. Australia escalated further in February 2026: the TGA reclassified melanotan II from Schedule 4 to Schedule 9 (prohibited substance), and in May 2026 issued 27 infringement notices (~AUD $101,412) to a single supplier — Australia is now the strictest market for mt-II. Available only as an unregulated research peptide; supply-chain quality is unverified and inconsistent. Not DEA-scheduled. Not listed on the WADA 2026 Prohibited List — direct PDF grep confirms melanotan, melanocortin, MSH, and bremelanotide are absent from the canonical 2026 PDF. Consistent with PT-141's absence — melanocortin receptor agonists do not fit any WADA prohibited category.

Melanotan II is not FDA-approved and is illegal to sell for human use in the US; case reports have linked it to mole changes and melanoma. It is not listed on the WADA Prohibited List as of the 2026 edition. VialWise is a research and educational reference, not medical advice — consult a licensed professional.

⚠️ For research and educational purposes only. Melanotan II is not approved by the FDA for any indication and is illegal to market, sell, or purchase for human consumption in the United States. It is similarly restricted in the UK (MHRA), Australia (TGA), New Zealand, and several other regulated markets. Information in this entry is informational, not medical advice. Always confirm dose calculations with the in-app calculator and consult appropriate professional guidance before any protocol decisions.

⚠️ Precision matters at low doses. Melanotan II is dosed in micrograms (mcg), not milligrams. Typical research-community doses ( per dose) at typical reconstitution concentrations ( for a vial reconstituted with 2–5 mL BAC water) produce small draws in the range on a U-100 syringe. At those draw sizes, even a one-unit error is a meaningful percentage of the dose. The precision concern is comparable to BPC-157 and GHK-cu — default to lower-concentration setups and verify draws against the in-app calculator before each injection.

⚠️ Melanotan II is not the same compound as bremelanotide (PT-141). Despite being structurally related, these are distinct compounds with substantially different regulatory and pharmacological status: - Melanotan II (this entry) = the parent compound, a 7-amino-acid cyclic α-MSH analog with the structure Ac-Nle4-Asp5-His6-D-Phe7-Arg8-Trp9-Lys10-NH2 (lactam-bridged). Broad-spectrum melanocortin receptor agonist at MC1R, MC3R, MC4R, and MC5R. Originally developed as a tanning agent. Not FDA-approved for any indication. Available only as an unregulated research peptide. - Bremelanotide (PT-141, Vyleesi) = a metabolite/derivative of mt-II that lacks the C-terminal amide group (replaced with hydroxyl/-OH). Same melanocortin receptor agonism profile but selective development for sexual function effects rather than tanning. FDA-approved as Vyleesi (NDA 210557, 2019) for hypoactive sexual desire disorder (HSDD) in premenopausal women. See [pt-141.md](./pt-141.md) for the bremelanotide entry. Palatin Technologies discontinued melanotan II development in 2000 in favor of bremelanotide because (a) bremelanotide has a more favorable side-effect profile for the sexual function indication; (b) bremelanotide's hydroxyl-vs-amide structural difference enables FDA-pathway development that the unmodified mt-II could not support. Researchers using mt-II from research-peptide supply chains are using the parent compound, not the FDA-approved Vyleesi derivative. Effects, side-effect profile, and supply-chain quality are not equivalent.

⚠️ Melanoma risk concern — case-report-level evidence; pre-existing nevus changes and atypical lesion development are characteristic patterns warranting prompt evaluation. Multiple published case reports (2011 onwards, with new cases still appearing in 2025–2026) describe: - Darkening of pre-existing moles within weeks of starting mt-II - Eruptive new nevi appearing during mt-II cycles - Atypical melanocytic nevi developing in mt-II users - Melanoma cases associated with mt-II use — two independent published case reports of melanotan-associated melanoma[⁵][⁶], plus a 2025 case report of oral mucosal malignant melanoma in a 22-year-old female who had used mt-II nasal spray[⁸] - Five synchronous primary melanomas in situ reported in 2026 in a single melanotan user who also had tanning-bed and anabolic-hormone exposure and a dysplastic-nevus background[⁹] — the most concerning recent addition to this literature - In familial melanoma syndromes (FAMMM), mt-II use has been reported to drive accelerated melanocytic-lesion changes The mechanism is biologically plausible: MC1R activation drives melanocyte proliferation and melanin production, and could theoretically promote proliferation of pre-existing atypical melanocytes. The evidence quality is case-report-level rather than RCT-level — no controlled trial has demonstrated causation, supply-chain quality of underground mt-II is highly variable, and the case reports involve unregulated supply with unknown purity. Researchers using mt-II should: (a) have a baseline full-skin examination by a dermatologist before starting; (b) photograph all moles for comparison monitoring; (c) discontinue immediately and seek dermatologic evaluation for any new mole, mole color/size/border change, or atypical lesion development; (d) avoid mt-II entirely if there is a personal or family history of melanoma, dysplastic nevus syndrome, or significant atypical mole burden.

⚠️ not listed on the WADA 2026 Prohibited List. Direct grep against the canonical WADA 2026 PDF confirms melanotan, melanocortin, MSH, and bremelanotide are all absent from the document.[¹³] This is consistent with melanocortin receptor agonists not fitting any WADA prohibited category (S0–S9). Fifth negative-WADA-listing entry in the library (joining GHK-cu, PT-141, Liraglutide, Thymosin α1). Researchers competing in WADA-tested sport should still confirm against the current annual edition before competition; the absence of a current listing is not a guarantee of absence in future editions.

Melanotan II is a synthetic cyclic heptapeptide analog of α-melanocyte-stimulating hormone (α-MSH), developed at the University of Arizona in the late 1980s and early 1990s by Victor Hruby, Mac Hadley, Robert Dorr, and Norman Levine — the same research group that established the foundational pharmacology of the melanocortin receptor system. The original program aim was to develop stable α-MSH analogs capable of stimulating melanogenesis as a photoprotective strategy — the hypothesis being that increasing baseline melanin density might reduce ultraviolet radiation damage to skin and decrease skin cancer risk. The compound was patented by the University of Arizona and licensed to Competitive Technologies, then to Palatin Technologies for clinical development.[²]

Mechanism. Mt-II is a broad-spectrum melanocortin receptor agonist that activates four of the five melanocortin receptor subtypes: - MC1R (skin/hair) — drives melanogenesis (the tanning effect) - MC3R and MC4R (CNS) — drive sexual function effects (spontaneous erections, libido elevation), appetite suppression, and energy expenditure - MC5R (exocrine glands) — minor role in sebum production and other peripheral effects - No significant MC2R binding (MC2R is the adrenocortical ACTH receptor; absence of MC2R activity means mt-II does not produce adrenal stimulation effects)

This broad-spectrum receptor profile distinguishes mt-II from PT-141/bremelanotide (which has the same receptor profile but with different selectivity) and from later-generation selective MC4R agonists like setmelanotide (Imcivree, FDA-approved 2020 for genetic obesity).

Development history and the bremelanotide pivot. The original Phase I clinical study of mt-II was published in 1996 by Dorr, Lines, Levine, Brooks, Xiang, Hruby, and Hadley as "Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study."[²] The trial established that mt-II produced reliable tanning at doses around/day SC. This pilot enrolled only 3 male volunteers, and it reported spontaneous penile erections qualitatively (occurring 1–5 hours post-dose, correlated with stretching and yawning) rather than as a proportion — an unanticipated observation that ultimately redirected the entire development program. A quantified figure comes from a later, separate trial: the Wessells 1998 double-blind placebo-controlled crossover study in men with psychogenic erectile dysfunction reported that "in 8 of 10 men treated with Melanotan-II clinically apparent erections developed."[⁷] Palatin Technologies discontinued mt-II development in 2000 in favor of developing bremelanotide (a deaminated metabolite of mt-II with hydroxyl rather than amide C-terminus) specifically for the sexual function indication. Bremelanotide subsequently advanced through FDA approval as Vyleesi (NDA 210557) in June 2019 for hypoactive sexual desire disorder (HSDD) in premenopausal women. Mt-II itself never advanced to NDA submission — the original tanning indication never produced sufficient safety data to support FDA approval, and the program's redirection to bremelanotide left mt-II as an abandoned development candidate. See [pt-141.md](./pt-141.md) for the bremelanotide entry.

Regulatory status (US — current). Mt-II is illegal to market, sell, or purchase for human consumption in the United States. The FDA has issued multiple warning letters to companies marketing mt-II as a "tanning injection," and has pursued border seizures and website takedowns of online sellers. Specific FDA enforcement actions include warning letters to Melanocorp and proceedings against Edward Manookian (Docket FDA-2015-N-4169).[¹] mt-II is not FDA-approved for any indication and is not available through any legal pharmaceutical or compounding-pharmacy channel in the US. All mt-II in current US use is obtained through unregulated research-peptide supply chains, with substantial variability in product purity and potency.

Regulatory status (international). Mt-II is similarly restricted for human use in the UK (MHRA), Australia (TGA), New Zealand, and several other regulated markets. Australia is now the strictest market: beyond the explicit consumer-warning advisory issued in 2023, the TGA reclassified melanotan II from Schedule 4 to Schedule 9 (prohibited substance) in February 2026, and in May 2026 issued 27 infringement notices totalling approximately AUD $101,412 to an individual alleged to have supplied melanotan II.[¹²] Enforcement in Australia is therefore active and current, not merely advisory. The compound has no human-use approval in any major Western regulatory framework. The "Barbie drug" media nickname (referencing the tanning + appetite-suppression + libido side-effect cluster) has produced periodic media attention to mt-II's underground use.

Regulatory status (sport — WADA). Mt-II is not listed on the WADA 2026 Prohibited List — direct PDF grep confirms absence of melanotan, melanocortin, MSH, and bremelanotide from the canonical document.[¹³] This is consistent with melanocortin receptor agonists not fitting any WADA prohibited category. Fifth negative-WADA-listing entry in the library (joining GHK-cu, PT-141, Liraglutide, Thymosin α1).

Common research interests. Despite the regulatory status, mt-II is one of the most-recognized research peptides in research-community use, primarily for: - Tanning (the primary use case) — sunless or low-UV-exposure tanning, particularly in low-melanin Fitzpatrick I-II skin types where natural UV tanning is limited - Spontaneous erections / libido elevation (frequently a desired secondary effect) — overlaps mechanistically with PT-141/bremelanotide but at a different selectivity profile - Appetite suppression — MC4R activation produces hypophagic effects; this is sometimes reported as a desired secondary effect - Photoprotective hypothesis (largely abandoned) — the original research-program rationale that increased baseline melanin reduces UV damage; this hypothesis is supported by general dermatology literature but has not been rigorously validated for mt-II-induced melanin specifically

The melanoma concern (load-bearing safety detail). Multiple published case reports (2011 onwards) describe melanocytic lesion changes in mt-II users — darkening of pre-existing moles, eruptive new nevi, atypical melanocytic nevi, and frank melanoma development.[⁵][⁶][⁸][⁹] The literature has continued to accumulate rather than settle: a 2025 report describes oral mucosal malignant melanoma in a young mt-II nasal-spray user,[⁸] and a 2026 report describes five synchronous primary melanomas in situ in a single melanotan user.[⁹] The mechanism is biologically plausible: MC1R activation drives melanocyte proliferation, and could theoretically promote proliferation of pre-existing atypical melanocytes or accelerate transformation of dysplastic lesions. The evidence is case-report-level rather than RCT-level, but the consistent pattern across multiple independent case reports — combined with the biological plausibility and the additional confounder of unregulated supply-chain purity — warrants explicit acknowledgment as a load-bearing safety concern in any responsible mt-II discussion.

Commonly reported

• Nausea — most common acute side effect; typically within 30–60 minutes of injection; often most pronounced in the first few doses of a cycle, attenuating with continued use
• Facial flushing — common in the first hour post-injection
• Spontaneous erections (male users) — common in the first few doses; may persist hours after injection; often attenuates within the first week of dosing
• Decreased appetite / hypophagia — MC4R-mediated; commonly reported, sometimes desired
• Yawning — uncommon but characteristic of melanocortin agonism
• Stretching ("yawn-stretch syndrome") — uncommon
• Generalized skin darkening — the intended effect
• Darkening of pre-existing moles — common; warrants monitoring (see Melanoma concern callout)
• New nevi (eruptive nevi) — uncommon but reported; warrants dermatologic evaluation
• Atypical melanocytic nevi — rare but reported; warrants dermatologic evaluation
• Lentigines (sun-exposed skin spots) — uncommon but reported
• Paradoxical depigmentation / leukoderma — a 2026 case report describes depigmented facial and neck patches following melanotan use in a patient with atopic dermatitis and alopecia areata[¹¹] — pigmentation effects are not uniformly in one direction

Serious

• New mole, mole change, or atypical lesion development — see Melanoma concern callout
• Melanoma cases reported — multiple independent case reports[⁵][⁶], including a 2025 oral mucosal malignant melanoma case in a nasal-spray user[⁸] and a 2026 case of five synchronous primary melanomas in situ in one user[⁹]
• Rhabdomyolysis — reported after unregulated melanotan I / II use in a 2026 PRISMA systematic review of 68 studies[¹⁰]
• Renal infarction — reported in the same 2026 systematic review of unregulated melanotan use[¹⁰]
• Priapism (prolonged, painful erection) — reported in the same 2026 systematic review[¹⁰]; a medical emergency requiring immediate care, and mechanistically consistent with MC3R/MC4R-mediated erectile effects
• Severe nausea or vomiting persisting beyond the first hour — uncommon but warrants dose reduction or discontinuation

Personal or family history of melanoma, dysplastic nevus syndrome (FAMMM), or significant atypical mole burden — see Melanoma concern callout

Active malignancy — theoretical contraindication based on melanocyte-proliferation mechanism

Pregnancy and lactation — no human data; default to contraindicated

Pediatric use — no data; should not be used in researchers under 18

Active dermatologic conditions affecting pigmentation (vitiligo, melasma) — pigmentation effects may be unpredictable

Severe cardiovascular disease — mt-II's CNS effects can produce transient blood pressure changes; caution in cardiovascular-compromised individuals

Regulatory note (US): Mt-II is illegal to market, sell, or purchase for human consumption in the United States. Use is outside any FDA-recognized supply chain or therapeutic framework.

Regulatory note (Australia): Mt-II was reclassified by the TGA from Schedule 4 to Schedule 9 (prohibited substance) in February 2026, with active enforcement — 27 infringement notices (~AUD $101,412) issued to a single alleged supplier in May 2026.[¹²] Supply and possession carry legal exposure in Australia well beyond the advisory-level status that preceded the reclassification.

Regulatory note (sport): Not listed on the WADA 2026 Prohibited List — confirmed by direct grep against the canonical 2026 PDF.[¹³] Fifth negative-WADA-listing entry in the library.

Peptide

A short chain of amino acids, the building blocks of proteins. Many compounds in this library are peptides.

Melanocortin receptor agonist

a compound that activates the receptors controlling pigmentation and other effects.

Case report

a published description of one or a few individual patients, not a controlled study.

Subcutaneous

An injection into the fatty layer just under the skin, rather than into a muscle or vein.

1. US Food and Drug Administration. Enforcement actions against Melanotan II marketing and distribution. Multiple FDA warning letters, border seizures, and administrative proceedings. Specific publicly-documented actions include: warning letters to Melanocorp (early 2010s); Notice of Opportunity for Hearing (NOOH) for Edward Manookian, Docket FDA-2015-N-4169 (August 5, 2016 hearing notice; ruling at fda.gov/media/128834/download; FDA Notice of Opportunity for Hearing at fda.gov/regulatory-information/electronic-reading-room/notice-opportunity-hearing-nooh-manookian-edward-8516). Source for: Mt-II's status as illegal for human consumption in the US; FDA active enforcement against marketing and distribution; absence of any legal pharmaceutical or compounding-pharmacy supply chain in the US.
2. Dorr RT, Lines R, Levine N, Brooks C, Xiang L, Hruby VJ, Hadley ME. (1996). Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study. Life Sciences, 58(20):1777–1784.(PMID 8637402)
3. Lan EL, Ugwu SO, Blanchard J, Fang X, Hruby VJ, Sharma S. (1994). Preformulation studies with melanotan-II: a potential skin cancer chemopreventive peptide. Journal of Pharmaceutical Sciences, 83(8):1081–1084 (August 1994).(PMID 7983590)
4. Gilhooley E, Daly S, McKenna D. (2021). Melanotan II User Experience: A Qualitative Study of Online Discussion Forums. Dermatology, 237(6):995–999 (published online 2 November 2021).(PMID 34464955)
5. Hjuler KF, Lorentzen HF. (2013). Melanoma associated with the use of melanotan-II. Dermatology (Karger), 228(1):34–36.(PMID 24355990)
6. Paurobally D, Jason F, Dezfoulian B, Nikkels AF. (2011). Melanotan-associated melanoma. British Journal of Dermatology, 164(6):1403–1405.(PMID 21564053)
7. Wessells H, Fuciarelli K, Hansen J, Hadley ME, Hruby VJ, Dorr R, Levine N. (1998). Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study. The Journal of Urology, 160(2):389–393.(PMID 9679884)
8. Yassin Alsabbagh A, Bhujel N, Singh RP. (2025). Melanotan II nasal spray: a possible risk factor for oral mucosal malignant melanoma? International Journal of Oral and Maxillofacial Surgery, 54(9):806–808.(PMID 40210573)
9. Vadner DJ, Smith S. (2026). Five primary melanomas in situ in a patient with recent tanning bed use, melanotan exposure, and anabolic hormone use. JAAD Case Reports, 73:111–114.(PMID 42328529)
10. Resnick G, Khajeh-Afzaly M, Yousefian F, Raza A, Issa NT. (2026). Insights into Tanning Biology and Tanning Products. The Journal of Clinical and Aesthetic Dermatology, 19(2):33–42.(PMID 41890775)
11. Ume A, Chambers S, Worswick S. (2026). Depigmented Facial and Neck Patches Following Melanotan Use in a Patient With Atopic Dermatitis and Alopecia Areata. Clinical and Experimental Dermatology (published 2026-05-29).(PMID 42212476)
12. Therapeutic Goods Administration (Australia). Melanotan II — Schedule 9 (prohibited substance) reclassification and 2026 enforcement action. TGA media release, Individual issued 27 infringement notices for allegedly supplying melanotan II (tga.gov.au/news/media-releases/individual-issued-27-infringement-notices-allegedly-supplying-melanotan-ii); TGA consumer safety blog, Don't risk using tanning products containing melanotan (tga.gov.au/news/blog/dont-risk-using-tanning-products-containing-melanotan). Source for: the Schedule 4 → Schedule 9 (prohibited substance) reclassification in February 2026; the May 2026 issuance of 27 infringement notices totalling approximately AUD $101,412 to a single alleged supplier; the "Australia is now the strictest market" framing in the status frontmatter, the international-regulatory paragraph, and the Contraindications section. This is an escalation well beyond the 2023 consumer-warning advisory that preceded it. The TGA media release confirms active 2026 enforcement; the Schedule 9 classification is corroborated across the release and secondary coverage. Added 2026-07-18.
13. World Anti-Doping Agency. The 2026 Prohibited List, International Standard (effective 1 January 2026). Canonical PDF: wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf (linked from the WADA landing page; local archival copy in `docs/legal/wada-2026-prohibited-list.pdf`). Melanotan II is not listed anywhere in the canonical 2026 PDF. Direct grep against the locally-archived PDF for "melanotan", "melanocortin", "MSH", and "bremelanotide" all returned zero hits, confirming mt-II's absence from the prohibited list. This is consistent with melanocortin receptor agonists not fitting any WADA prohibited category (S0–S9).

• PT-141 (Bremelanotide) — discussed together in this entry's stacks section
• Afamelanotide — same mechanism class
• AHK-Cu — shared research area
• Clomiphene / Enclomiphene — shared research area
• GHK-Cu — shared research area
• GLOW — shared research area