Melanotan II
Melanotan II is a synthetic cyclic heptapeptide analog of alpha-MSH that non-selectively agonizes multiple melanocortin receptors (MC1R, MC3R, MC4R, MC5R), producing a broad range of effects including eumelanin-based skin tanning, appetite suppression, and CNS-mediated sexual arousal. The tanning effect — occurring even without significant UV exposure — arises from MC1R activation driving melanin synthesis in melanocytes, while the libido and erectile effects are primarily mediated through MC4R in the CNS. Unlike the approved afamelanotide (Melanotan I), Melanotan II has never completed regulatory clinical trials and is not approved by the FDA, EMA, or any comparable agency, existing entirely outside formal pharmaceutical channels. Reported adverse effects include nausea, spontaneous erections, facial flushing, darkening and proliferation of moles (melanocytic nevi), and unresolved theoretical oncological concerns from unregulated melanocyte stimulation.
Evidence last reviewed: 19 Apr 2026
Not a routine supplement — not recommended for self-directed use.
Information here is educational only, not a recommendation to use. See our Safety page.
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Evidence is from research or clinical settings — does not imply safety outside supervised contexts.
The evidence for Melanotan II is limited and primarily derived from small studies and case reports, indicating potential effects on skin pigmentation and libido. However, the low quality of evidence and lack of regulatory approval highlight significant gaps in safety and efficacy data.
Libido enhancementHealthy adults · Case seriesLow
Users reported increased libido following administration of Melanotan II.
Erectile function (spontaneous erections)Healthy adult males (n=3) · Phase I single-blind placebo-controlled pilot study (incidental observation)Low
Spontaneous penile erections lasting 1–5 hours were intermittently experienced after MT-II dosing, accompanied by a stretching and yawning complex. Onset correlated with dose level. Erectile response was an incidental finding; efficacy as a primary endpoint was not evaluated in this safety study.
Skin pigmentation (tanning)Healthy adult males (n=3) · Phase I single-blind placebo-controlled pilot studyLow
Two of three subjects showed measurable increased pigmentation in face, upper body, and buttock after only 5 subcutaneous doses. Pigmentation was confirmed by quantitative reflectance measurement and visual perception one week after dosing ended.