Melanotan II is a synthetic cyclic analogue of alpha-melanocyte-stimulating hormone, developed originally as a photoprotection concept. It is non-selective across melanocortin receptors, which is the root of both its effects and its problems.

It is in this compendium because it is widely used outside medical supervision and has an unusually well-documented harm record for an unapproved peptide. A case series literature rather than a theoretical risk profile. The related but distinct compound afamelanotide, a selective MC1R agonist, did complete development and is approved for a rare photodermatosis; the two are frequently confused.

Melanotan II agonises MC1R, MC3R, MC4R, and MC5R with limited selectivity.

MC1R agonism on melanocytes drives eumelanin synthesis and the pigmentation effect. MC4R agonism in the central nervous system produces the appetite suppression and the sexual-response effects that led to bremelanotide's development. MC3R and MC5R contributions to the overall profile are less well characterised.

The non-selectivity is not a footnote. It means every dose engages pathways unrelated to the intended effect, including stimulation of melanocytes throughout the skin.

No approved indication and no adequately powered efficacy or safety programme. Early human studies established the pigmentation and erectile-response effects; nothing progressed to a completed programme for the compound itself.

What does exist in quantity is a case report and case series literature describing adverse events, which is the unusual feature of this entry. Anecdotes are weak evidence that something works and strong evidence that something can happen, and this is the clearest example of that asymmetry in the catalogue.

This is the section that matters for this entry.

Case reports and series describe new and changing melanocytic naevi, darkening and enlargement of existing moles, and melanoma diagnosed in users. Including cases where the pigmentary changes delayed recognition. Whether melanotan II causes melanoma or obscures its detection is unresolved; both are bad.

Also documented: nausea and vomiting, facial flushing, spontaneous erections, dizziness, and rhabdomyolysis in case reports. Because it is injected using unregulated material, infection and contamination risk are real and independent of the pharmacology.

If you have used this and have a mole that has changed, that is a dermatologist appointment, not a forum thread.

Not approved for human use anywhere. Multiple national regulators have issued explicit public safety warnings against it. Sold illegally in many jurisdictions as a tanning agent, frequently through channels with no quality control whatsoever.

Afamelanotide, a different and selective MC1R agonist, is approved for erythropoietic protoporphyria in some jurisdictions and is not this compound.