Melanotan II

What it is

Melanotan II binds several melanocortin receptors, described in the literature as MC1R, MC3R, MC4R and MC5R, rather than acting selectively on just one as some related peptides do. MC1R activation in skin cells drives melanin production, while MC4R activation in the brain is linked to appetite and sexual arousal pathways.

Because these receptors show up in more than one body system, research on Melanotan II has split along those same lines, one line of study on pigmentation and sun protection, and a separate line on erections and sexual desire in men with erectile dysfunction, both grounded in the same underlying receptor family rather than in two unrelated mechanisms.

How it is studied

Human studies have given injections under the skin over periods from a single injection up to two weeks of repeated injections, tracking skin pigment in one line of research from an early phase 1 trial, and penile rigidity, sexual desire and side effects using real time monitoring equipment in a separate line of research in men with erectile dysfunction.

What studies report

• A pilot phase 1 study in three men given five small injections over two weeks reported measurable skin pigmentation increases in the face, upper body and buttock, alongside side effects that included mild nausea, and, at the highest amount tested, drowsiness and fatigue in one of two subjects. [1]
• That same pilot study reported spontaneous, unstimulated penile erections lasting one to five hours after injection in the men studied, often preceded by stretching and yawning. [1]
• A placebo-controlled crossover trial in ten men with erectile dysfunction not linked to any physical cause reported that a single injection produced clinically apparent erections in most participants, with markedly longer duration of firm erection than placebo. [2]
• A separate placebo-controlled crossover trial in ten men whose erectile dysfunction did have an identified physical cause reported a similar pattern, with more reported erections and higher self-reported sexual desire after Melanotan II than after placebo, alongside nausea that was severe in some injections. [3]

What is not known

None of the human trials located for this entry tested Melanotan II in women; the description of an effect on female sexual arousal that sometimes circulates about this compound could not be traced to a published Melanotan II trial and is not repeated here. All of the sexual function trials found were small, short studies in men given a single or twice-repeated injection, so it is not known whether the effect holds up with repeated use over months, or how significant the nausea and drowsiness seen at higher amounts would be outside a monitored clinical setting. Long term skin and mole safety over repeated use is not addressed in the studies reviewed here, and whether the pigmentation and sexual arousal effects can be separated from one another pharmacologically is not resolved in this record.

Reported adverse findings

• Across the cited trials, nausea was the most consistently reported side effect, described as severe in a minority of injections in the organic erectile dysfunction trial, alongside stretching, yawning, and, at the highest amount tested in the pilot study, drowsiness and fatigue. [1][3]

Regulatory status

No approval for human use has ever come from the United States Food and Drug Administration or Health Canada for Melanotan II. Every jurisdiction covered in this record treats it as an unapproved research compound.