Melanotan II : données probantes, mécanisme et limites

Melanotan II is a synthetic cyclic analog of alpha-melanocyte-stimulating hormone (alpha-MSH). It is a nonselective agonist across several melanocortin receptor subtypes. It is sold online for tanning and for sexual effects, but it is not an approved medicine in the United States or Canada.

It should not be confused with afamelanotide, an approved alpha-MSH analog sold as SCENESSE for adults with a history of phototoxic reactions from erythropoietic protoporphyria, or with bremelanotide, sold as VYLEESI. They are different molecules with different receptor activity, formulations and regulatory histories.

Activation of the MC1 receptor on melanocytes increases cyclic-AMP signaling and promotes melanin production, which darkens skin. Activity at central MC3 and MC4 receptors can influence appetite, arousal and autonomic output. Because Melanotan II is not receptor selective, a desired effect cannot be cleanly separated from effects at other melanocortin receptors.

Preclinical: medicinal chemists have used Melanotan II as a starting scaffold to design more selective melanocortin agonists. That work is laboratory chemistry, not evidence about outcomes in people.

Human studies: a University of Arizona group gave Melanotan II to 20 men with psychogenic or organic erectile dysfunction in a double-blind, placebo-controlled crossover design. Most had erections without sexual stimulation, and more reported increased desire after Melanotan II than after placebo. Nausea and yawning were frequent, and some participants had severe nausea.

These studies were small and old. Reviews summarize clinical signals alongside adverse reports, but there is no modern approval-quality trial program. The evidence supports biological activity, not a favorable balance of benefit and risk.

A 2017 dermatology review describes growing case reports of melanocytic changes in existing moles and newly emerging, sometimes dysplastic, nevi with unregulated use of Melanotan I and II. Four case reports described melanomas arising from existing moles during or shortly after use. The authors note that conclusive evidence linking the two is lacking. Sexual effects can include prolonged erection, and FDA's summary below includes priapism.

FDA's compounding list cites published case reports of serious adverse events, including melanoma, posterior reversible encephalopathy syndrome, sympathomimetic toxidrome and priapism. Products sold online may differ in identity, purity, sterility and storage, so reports cannot always separate the molecule's effects from product-quality problems. A tan from Melanotan II does not replace sun protection or skin checks.

Melanotan II is an unapproved drug in the United States. FDA lists it among bulk substances nominated for compounding that were placed in category 2 and then withdrawn by the nominators. In Canada it is not an authorized drug; Health Canada's Drug Product Database lists no product, and its April 2026 advisory names Melanotan I and II among seized unauthorized peptides. It is not named on the 2026 WADA Prohibited List.