Melanotan 1 vs 2: Research Data

Melanotan 1 vs 2 at a Glance

Sources for each row are given in the sections below.^{[1][8][2][9][6]}

What Is Melanotan I (Afamelanotide)?

Melanotan I is a synthetic analogue of alpha melanocyte stimulating hormone (α-MSH) with two substitutions, norleucine at position 4 and D-phenylalanine at position 7, which belong to a family of superpotent, prolonged-acting analogues. PubChem lists it as afamelanotide, a 13-amino-acid linear peptide of formula C₇₈H₁₁₁N₂₁O₁₉ (1,646.8 g/mol).^[1] It was developed alongside Melanotan II, with Melanotan I tested clinically for skin tanning and Melanotan II for erectile dysfunction; its developers suggested a tan produced without UV exposure might lower the risk of skin cancer, a possibility raised in a 2006 review rather than shown in trials.^[4]

In an early human study in three male volunteers, Melanotan I given by subcutaneous injection produced significant tanning of the forehead, arms and neck that was still present three weeks later; given by mouth it was not detected in blood. Side effects were minimal, mainly occasional stomach upset and facial flushing.^[10]

What Is Melanotan II?

Melanotan II is a shorter, cyclic heptapeptide built on residues 4 to 10 of α-MSH and closed by a lactam bridge, with formula C₅₀H₆₉N₁₅O₉ (1,024.2 g/mol).^[6][8] It activates multiple melanocortin receptors rather than mainly MC1R, which is why it affects sexual function as well as skin pigmentation.^[9] Bremelanotide (PT-141) was later developed from it.^[4]

Melanotan II is sold online as a tanning agent in injection and nasal spray forms, outside any regulated supply.^[11][12][13] A 2026 review of peptides in sexual medicine noted that it remains accessible through unregulated markets, with concerns about product quality and incompletely characterised adverse effects.^[14]

How They Work: Alpha Melanocyte Stimulating Hormone and Melanocortin Receptors

Both peptides imitate α-MSH. Melanotan products are designed to induce melanogenesis and eumelanin production, the dark pigment behind a tan, without sun exposure.^[11] Afamelanotide binds predominantly to MC1R, the receptor on pigment cells.^[2] Melanotan II is a non-selective melanocortin receptor agonist, and its early studies recorded erections, yawning, reduced appetite and greater sexual desire alongside pigmentation.^[9][15] This difference in receptor selectivity, a broader receptor profile for Melanotan II, is the main pharmacological difference behind the Melanotan 1 vs 2 comparison.

Effects of Melanotan in Human Studies

Melanotan II and Psychogenic Erectile Dysfunction

In a 1996 pilot phase I study in healthy volunteers, Melanotan II produced increased pigmentation in the face, upper body and buttocks of two subjects one week after the last dose, published in Life Sciences. Mild nausea occurred at most dose levels, and a stretching and yawning complex appeared alongside spontaneous erections lasting one to five hours; the highest level tested caused somnolence and fatigue in one of two subjects.^[6]

A double-blind, placebo-controlled crossover trial in ten men with psychogenic erectile dysfunction found clinically apparent erections in eight after Melanotan II, without sexual stimulation, with nausea, stretching, yawning and reduced appetite reported more often than on placebo.^[15] A report on 20 men with psychogenic or organic erectile dysfunction, published in the International Journal of Impotence Research, reported erections in 17 and greater sexual desire after 68% of Melanotan II doses against 19% of placebo doses; 12.9% had severe nausea at the level tested.^[9]

Afamelanotide in Erythropoietic Protoporphyria

Melanotan I, now called afamelanotide, was developed into a treatment for erythropoietic protoporphyria (EPP), a rare disease in which light exposure causes severe pain. In two randomized, placebo-controlled trials (74 patients in the EU, 94 in the US), afamelanotide implants increased pain-free time in direct sunlight, reduced phototoxic reactions in the EU trial and improved quality of life. Adverse events were mostly mild, and serious adverse events were not thought to be drug related.^[5]

Melanotan Side Effects: Most Common Side Effects and Serious Risks

Afamelanotide (Melanotan I): What the Label Reports

In the US label, adverse reactions in more than 2% of patients through month 6 included implant site reactions (21% against 10% with a vehicle implant), nausea (19% against 14%), oropharyngeal pain (7%), cough (6%), fatigue (6%), skin hyperpigmentation (4% against 0%) and melanocytic nevus (4% against 2%). Serious allergic reactions (hypersensitivity, including anaphylaxis) have been reported after marketing. Because it can darken existing moles and freckles, the label recommends a full-body skin examination twice a year.^[2]

Serious Side Effects After Melanotan Use: Melanoma, Kidney Injury and Melanotan-Induced Priapism

• Melanoma. A 2025 case report described oral mucosal melanoma in a 22-year-old woman who had used a Melanotan II nasal spray for tanning, and a 2026 report described five melanomas in situ in a patient who had also had UV exposure from tanning beds and used other drugs, including anabolic hormones. Single cases cannot establish cause.^[12][16]
• Melanotan-induced priapism. A BMJ Case Reports patient developed low-flow priapism after injecting melanotan and had not recovered erectile function four weeks later.^[17]
• Rhabdomyolysis and kidney injury. One man developed sympathomimetic toxicity, rhabdomyolysis and kidney dysfunction after injecting an internet product confirmed as Melanotan II; another case of renal infarction was most likely attributed to it.^[11][18]
• Pigment changes. A 2026 case report in Clinical and Experimental Dermatology described depigmented patches on the face and neck after melanotan use.^[19]
• Review evidence. A 2026 systematic review of 68 studies on sunless tanning products found that unregulated melanotan I and II use has caused serious side effects, including rhabdomyolysis, renal infarction and priapism.^[7]

FDA’s compounding safety page summarises the same signals for Melanotan II: a possible immunogenicity risk from aggregation or peptide-related impurities, and published case reports of melanoma, posterior reversible encephalopathy syndrome, sympathomimetic toxidrome and priapism.^[20] A study of online forums, published in Dermatology, found that melanotan users also face potential harms from unregulated products that may be contaminated and from combined sunbed exposure.^[13]

Regulatory Status: FDA Approval, EMA and WADA

Which Has More Human Evidence?

Afamelanotide, by a wide margin. It has two randomized controlled trials published in the New England Journal of Medicine and an approved label with placebo-comparison adverse-event rates.^[5][2] Melanotan II has a pilot phase I study and two small erectile dysfunction studies from the 1990s, followed mainly by case reports, a qualitative forum study and reviews.^{[6][15][9][13][7]} Those approval and evidence gaps are why the two names should not be treated as interchangeable, and why claims made for an online “Melanotan I” product cannot borrow the Scenesse trial data.

Melanotan II vs PT-141

PT-141 (bremelanotide) is a Melanotan II analogue that went on to FDA approval in 2019 for hypoactive sexual desire disorder in premenopausal women.^[4][23] The two share a melanocortin scaffold but have very different source trails. See PT-141 vs Melanotan II and the PT-141 melanocortin research review.

What the Research Does Not Yet Show

• Controlled safety data for Melanotan II. No large randomized trial has been published, so the frequency of serious events is unknown.^[7][14]
• Cause and effect for melanoma. The melanoma cases involve confounders such as sunbed use, and single reports cannot show causation.^[16][12]
• Afamelanotide outside EPP. Its approvals cover erythropoietic protoporphyria only.^[2][3]

Melanotan II for Laboratory Research

Remy Research supplies Melanotan II as a research chemical for in-vitro research only, as the Genovare Melanotan II 50mg AQ pen. Each product page carries its batch testing details. Remy Research does not supply Melanotan I or afamelanotide.