What it is
Melanotan II is a lab-made, ring-shaped version of part of α-MSH, the hormone that tells skin cells to make the dark pigment melanin. Closing the chain into a ring made it very potent and long-lasting.
It switches on several related receptors, including ones in the brain, not just the one in skin. That is why the early human studies saw tanning alongside effects the researchers had not been looking for: spontaneous erections, nausea, yawning and reduced appetite.
No medicine containing Melanotan II has ever been approved anywhere. US and Australian regulators have acted against its sale as a tanning injection or nasal spray, the UK regulator says it has repeatedly removed melanotan products from sale, and testing has shown that such products often do not contain what the label says.
Melanotan II (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, C50H69N15O9, 1024.2 g/mol) is a cyclic heptapeptide based on α-MSH(4-10). A lactam bridge between Asp5 and Lys10 constrains the His-D-Phe-Arg-Trp core, and Nle4 with D-Phe7 carries over the stability gains of afamelanotide. Its developers describe it as a non-selective melanocortin receptor agonist (Wessells et al. 2000), and pharmacology studies use it as an MC3R and MC4R agonist. Melanocortin receptor agonism on melanocytes drives eumelanin synthesis via Gs and cAMP; central melanocortin receptor agonism is thought to explain the erectile, appetite-suppressing and yawning–stretching effects.
No published human pharmacokinetic study was found for this article. Bremelanotide, the approved drug in the same family, differs from Melanotan II only by a C-terminal carboxylic acid in place of the amide, and its label reports a subcutaneous half-life of about 2.7 hours; that figure should not be assumed to apply to Melanotan II.
Who made it and when
Melanotan II was designed at the University of Arizona in the late 1980s by the same chemistry and biology group, led by Victor Hruby and Mac Hadley, that produced Melanotan I. The goal was a more potent sunless tanning agent.
In a tiny 1996 safety study of three men, two developed tans, and the men also reported erections that had not been the aim of the study. A 1998 study then tested it in ten men with erectile problems. That side effect became the more interesting lead: a company called Palatin Technologies later developed bremelanotide, a near-identical molecule, which became the approved drug Vyleesi. Melanotan II itself was never taken through full development.
Al-Obeidi, Hadley, Hruby and colleagues described cyclic lactam α-MSH analogues designed with molecular-dynamics modelling in J Med Chem in 1989. Dorr et al. (Life Sci 1996) reported a single-blind, alternating-day, placebo-controlled pilot in three healthy men at 0.01 to 0.03 mg/kg subcutaneously, noting increased pigmentation in two of the three men, intermittent spontaneous erections for 1–5 hours after dosing depending on the dose, mild nausea and, at 0.03 mg/kg, grade II somnolence and fatigue in one man. Wessells et al. (J Urol 1998) ran a double-blind crossover in 10 men with psychogenic erectile dysfunction at 0.025 mg/kg.
Palatin Technologies developed bremelanotide (PT-141), which differs from Melanotan II only at the C-terminus; early Palatin studies used an intranasal formulation (Diamond et al. 2004) before the programme moved to subcutaneous injection. No company is known to be developing Melanotan II itself for approval. A 2026 Phase 2 registration in China (NCT07437560) lists a small company sponsor, Hudson Biotech, gives no dose or route, and describes itself as an “example” trial record, so whether it is a substantive study is unclear.
What the data say
The controlled human evidence is very small: one study of three men and one of ten, both from the 1990s, plus a thinly documented Phase 2 vitiligo trial registered in China in 2026 that has not reported. Those early studies showed skin darkening and erections, with nausea as the most common complaint.
Most of what is known about safety comes from case reports of people who bought unregulated products. Doctors have described moles that suddenly darkened or multiplied, a small number of melanomas, painful prolonged erections, a brain-swelling syndrome called PRES, and muscle breakdown. Case reports cannot prove the drug caused these problems, and the products involved were of unknown content. No study has measured whether Melanotan II protects against skin cancer.
Controlled data: n=3 (Dorr 1996) and n=10 (Wessells 1998; erections in 8 of 10, mean tip rigidity above 80% for 38.0 vs 3.0 minutes, p=0.0045). Wessells et al. also reported a study in men with organic erectile dysfunction (Urology 2000). NCT07437560 (Phase 2, n=60 planned, stable non-segmental vitiligo, adjunct to narrowband UVB) began recruiting in February 2026; it is not registered as an FDA-regulated study and has posted no results.
Case literature: Habbema et al. (Int J Dermatol 2017) reviewed reports of eruptive and changing naevi with unregulated melanotan use and four melanomas arising from existing moles during or shortly after use, noting that conclusive evidence of causation is lacking. Further reports include posterior reversible encephalopathy syndrome (Kaski et al., Ann Intern Med 2013), priapism (Devlin 2013; Dreyer 2019; Mallory 2021), systemic toxicity with rhabdomyolysis (Nelson 2012) and, in 2026, five primary melanomas in situ in one patient who also used tanning beds and anabolic hormones (Vadner and Smith, JAAD Case Rep). FDA cited melanoma, PRES, sympathomimetic toxidrome and priapism when it placed Melanotan II in Category 2.
Regulatory picture
Three separate facts. Approval: no product containing Melanotan II is approved by the FDA or any other major regulator. Compounding: in 2023 the FDA put Melanotan II in “Category 2”, its list of substances that may pose significant safety risks in pharmacy compounding. By April 2026 the FDA listed it as withdrawn from that category by whoever nominated it; that does not make it allowed, because it is still not on the list of permitted compounding ingredients. Enforcement: the FDA warned an American seller in 2007, and the owner was later convicted. The UK’s MHRA says it has repeatedly removed melanotan products from sale for more than a decade. In August 2026 Australia’s TGA reported fines over illegal supply, and its laboratory found badly dosed nasal sprays.
Approval: none. No IND-stage programme with a US sponsor could be verified.
Compounding: Melanotan II was placed in Category 2 of the interim 503A policy on 2023-09-29. FDA’s page updated 2026-04-22 lists it among substances “previously in category 2 of the interim policies” that “were withdrawn by the nominators”. It is not a component of an approved drug, has no USP monograph and is not on the 503A bulks list (21 CFR 216.23), and it was not reviewed at the July 2026 Pharmacy Compounding Advisory Committee meeting. This article records compounding status as unknown.
Enforcement: FDA issued a warning letter on 2007-08-30 to a US company selling Melanotan II; its president pleaded guilty in 2015 to conspiracy under 18 U.S.C. 371 and FDA proposed permanent debarment on 2016-08-05. In Australia Melanotan II is a prescription-only medicine with no product on the ARTG; the TGA’s advisory of 2026-08-17 reported 27 infringement notices, paid in May 2026. The UK’s MHRA stated in 2021 that melanotan tanning products are not automatically medicines under UK law but that it had removed such products from sale for over 10 years. In sport it is not named on WADA’s list and falls under S0, non-approved substances.
