A synthetic, long-lasting copy of the pigment hormone alpha-MSH, sold illegally online as a tanning injection and nasal spray. Small studies decades ago showed it darkens skin and triggers erections, but it hits several melanocortin receptors at once and has been linked to new and darkening moles, melanoma, kidney injury, and muscle breakdown. No regulator has approved it.
Melanotan II is a cyclic version of a seven-amino-acid core of alpha-melanocyte stimulating hormone, the hormone that tells pigment cells to make melanin. The ring structure makes it far more potent and longer lasting than the natural hormone. It activates the melanocortin 1 receptor on skin melanocytes, which drives melanin production and tanning. Because it is not selective, it also activates melanocortin receptors in the brain that control appetite and sexual arousal.
Injected ring peptide (1/7)
Melanotan II, a ring-shaped copy of the pigment hormone alpha-MSH, is injected.
That brain activity explains the odd cluster of effects seen in the first volunteers: yawning and stretching, nausea, drowsiness, and spontaneous erections lasting 1 to 5 hours after a dose. The same receptor family regulates energy balance, which is why appetite falls. Stimulating melanocytes throughout the body also stimulates the cells inside moles, and case reports describe moles multiplying and darkening within 24 hours of a single injection. Unlike sunscreen, the pigment it produces offers no proven protection against UV damage.
Melanotan II is sold online as a tanning agent, in vials for injection and more recently as nasal sprays, and also as a sexual stimulant. In a pilot study in 3 men, five low doses given on alternate days darkened the skin of the face and upper body within a week. In a crossover study of 10 men with psychogenic erectile dysfunction, 8 developed clinically apparent erections after injection. Those studies tested safety and biological effect, and no larger trial of the compound as a tanning or sexual drug was ever completed.
Nobody is developing Melanotan II as a medicine, so every product on the market is unapproved and unverified. Australia's TGA says melanotan products are illegally promoted and sold online, are not approved for sale or use as tanning agents, and may contain toxic, poor quality, or counterfeit ingredients. The FDA lists compounded Melanotan II among substances that may present significant safety risks, and Health Canada names it among seized unauthorized peptides. A related but distinct compound, afamelanotide, is an approved implant for a rare light-sensitivity disorder and is not interchangeable with melanotan.
Human efficacy data are a few small, old studies: a pilot phase 1 study in 3 male volunteers that showed tanning, a crossover trial in 10 men with psychogenic erectile dysfunction, and related work on sexual function. Since then the literature has shifted to harms, with case reports of eruptive moles, melanoma, systemic toxicity, priapism, and kidney injury, plus laboratory analyses of black-market vials. A 2017 review concluded that illegal melanotans carry risks from unknown preparation, dosing, and administration on top of the melanocytic changes. No controlled safety study of modern products exists.
The core unknown is whether the compound itself, the contaminants in unregulated vials, or the sun exposure users seek is responsible for each reported harm, since all three travel together. Whether repeated melanocyte stimulation raises melanoma risk over years has never been studied prospectively, and the case reports cannot prove causation. Nothing is known about long-term effects on appetite, blood pressure, or the kidney. Regulators note that buyers have no way of knowing what the vials contain, regardless of the label.
Nausea, flushing of the face, headache, loss of appetite, yawning and stretching, drowsiness, and unwanted erections are the common effects in volunteers and users. Darkening of existing moles and sudden eruptions of new moles are well documented, and melanoma has been reported in people using melanotan, including a 20-year-old woman who combined it with sunbeds. Case reports also describe kidney dysfunction, a sympathomimetic reaction with a racing heart and muscle breakdown after a 6 mg injection, priapism, and swelling of the brain. Because the products are unregulated, dose errors and contaminated vials add to these risks.
No regulator has approved this compound, and no company is seeking approval.
Melanotan II has no approval from the FDA or any other regulator, and its only legal use is in research. The FDA lists compounded Melanotan II among bulk substances that may present significant safety risks and cites case reports of melanoma, posterior reversible encephalopathy syndrome, sympathomimetic toxicity, and priapism. Australia's TGA says it is illegal to supply melanotan tanning products and that they are not approved for sale or use, while Health Canada lists Melanotan I and II among seized unauthorized injectable drugs. The approved melanocortin drug afamelanotide is a different product with a narrow medical indication.