Melanotan II
A synthetic analogue of alpha-melanocyte-stimulating hormone (α-MSH) used to darken skin (tanning) and, as a side effect, increase libido and cause spontaneous erections. It has some early human study data but was never brought to market, and is sold illegally as an unlicensed injectable. Notable for nausea, facial flushing, and darkening or proliferation of moles.
01 Overview
Melanotan II (MT-II) is a cyclic non-selective melanocortin receptor agonist developed from research at the University of Arizona into α-MSH analogues. By activating MC1R it stimulates melanin production, producing tanning with less UV exposure; via MC4R it also drives sexual arousal — the erectile effect observed in early trials led to the development of the FDA-approved drug bremelanotide (PT-141).
What is evidenced: small early-phase human studies confirm it produces tanning and can induce erections. What is not: any licensed product, long-term safety data, or standardised dosing. Because it is non-selective, users get tanning plus unwanted MC4R effects (nausea, appetite suppression, arousal). Dermatologists have raised concern that it darkens existing moles and may mask or promote melanoma; case reports link it to new or changing melanocytic lesions.
02 Mechanism
Non-selective melanocortin receptor agonist. Activation of MC1R on melanocytes increases eumelanin synthesis (tanning); activation of MC4R in the central nervous system drives sexual arousal and suppresses appetite.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Loading anecdotal | 250–500 mcg/day | SubQ | Low starting dose to build pigment while limiting nausea. Not a licensed regimen. |
| Maintenance anecdotal | 500–1000 mcg/wk | SubQ | Once tan is established, dosed once or twice weekly to maintain. Convention-based. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Skin tanningIncreased melanin and darker skin confirmed in early human studies, even with minimal UV exposure. | Visible within 1-2 weeks | Clinical | |
| Increased libido / spontaneous erectionsErectogenic and pro-libido effects documented in early trials; basis for the derivative drug PT-141. | Clinical | ||
| Appetite suppressionReduced appetite commonly reported, consistent with MC4R activation. | Anecdotal |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Nausea and facial flushingNausea, flushing and yawning are common shortly after injection, particularly during loading. | Mild | Most users, especially early doses | Clinical | |
| Darkening and proliferation of moles / melanoma concernNew naevi and darkening or enlargement of existing moles are frequently observed; case reports describe melanoma diagnosed in users, and the pigment changes can mask early melanoma. | Severe | Frequent darkening; melanoma link reported | Observational | |
| Blood pressure and cardiovascular effectsTransient blood-pressure changes and priapism (prolonged painful erection) have been reported. | Moderate | Occasional | Anecdotal |