Melanotan II
A cyclic melanocortin receptor agonist that increases skin pigmentation; precursor research peptide that led to bremelanotide.
In plain English
Melanotan II is a synthetic, cyclic analog of alpha-melanocyte-stimulating hormone (α-MSH) that activates multiple melanocortin receptors, including MC1R (driving skin pigmentation) and MC4R (influencing sexual arousal). It was originally developed as a potential photoprotective agent but never reached regulatory approval. Its bremelanotide derivative (PT-141 / Vyleesi) did. Despite this, Melanotan II is widely sold on the grey market for tanning and arousal effects. UK and European regulators have repeatedly warned against its use, citing adverse events including darkened moles, nausea, blood pressure changes, and reports of melanoma in users.
What it is
Melanotan II is a synthetic, cyclic heptapeptide analog of α-MSH, acting as a non-selective melanocortin receptor agonist.
Mechanism (summary)
Activation of MC1R on melanocytes increases melanin production and skin darkening. MC4R activation in the CNS influences appetite and sexual arousal. MC3R activity is more complex.
Why people research it
- Photoprotection via increased melanin
- Erectile function and sexual arousal
- Cosmetic skin tanning (off-label/grey-market use)
Human evidence
Small academic trials have shown reliable increases in skin pigmentation. Sexual-arousal effects in men with erectile dysfunction were observed in early-phase studies and motivated the derivative PT-141. No Phase 3 program in tanning ever advanced to approval.
Animal / lab evidence
Robust effects on skin pigmentation in animals; consistent CNS effects on appetite and arousal.
Key studies
Each summary explains the design, what was found, and what it doesn't prove.
Volunteers using Melanotan II in a small trial reliably became more tan — measured by an instrument, not just by eye.
The UK's drug regulator publicly told the public not to use Melanotan II.
History
Developed in the 1980s at the University of Arizona as a potential photoprotective agent. The bremelanotide derivative was later approved as Vyleesi for HSDD.
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