Research Only Sexual & Reproductive Health

Melanotan II

also known as: MT-II, MT2, melanotan 2, MT-2, Barbie drug

An unapproved cyclic heptapeptide melanocortin agonist marketed for tanning and sexual function — strongly associated with melanocytic changes and dysplastic nevi in case reports. Not recommended.

A cyclic heptapeptide non-selective melanocortin agonist developed at the University of Arizona in the 1990s, now sold as an unregulated research chemical for tanning and sexual effects despite repeated case reports of melanocytic changes, eruptive nevi, and melanoma in situ.

Mechanism of action

Non-selective agonist at MC1R (melanocyte stimulation → melanin production and tanning), MC3R and MC4R (central — appetite suppression and sexual arousal via hypothalamic pathways), and MC5R (sebaceous gland stimulation). The central MC4R agonism underlies both the increased libido/spontaneous erections reported by users and the adverse effects (nausea, yawning, flushing). MC1R agonism drives eumelanin synthesis but also stimulates melanocyte proliferation — the likely mechanism behind the mole changes and atypical nevi reported in case series.

Primary uses

Unregulated tanning (off-label community use)
Unregulated sexual function enhancement (off-label community use)
Historical tanning research

Typical dosing

0.25–1 mg daily loading, then 2–3× weekly (subcutaneous)

Community dosing only. NOT MEDICAL GUIDANCE. Multiple case reports of melanocytic changes, dysplastic nevi, and melanoma in situ associated with use — including at least one case from a regulated compounding pharmacy.

Regulatory status

Not approved by any regulatory body. Development discontinued by Palatin Technologies in 2000 in favor of its metabolite PT-141 (bremelanotide). Sold only through research-chemical and unregulated online channels. Health authorities in Australia, the UK, and the US have issued public warnings.

References

[pubmed] Langan EA, et al. "Melanotropic peptides: more than just \"Barbie drugs\" and \"sun-tan jabs\"?" Br J Dermatol, 2010;163:451-455.
[pubmed] Paurobally D, et al. "Melanotan-associated melanoma." Br J Dermatol, 2011;164:1403-1405.
[review] Habbema L, et al. "Risks of unregulated use of alpha-melanocyte-stimulating hormone analogues: a review." Int J Dermatol, 2017;56:975-980.

Related peptides

PT-141

An FDA-approved melanocortin agonist for acquired, generalized hypoactive sexual desire disorder in premenopausal women.

Afamelanotide

An FDA-approved selective MC1R agonist marketed as Scenesse — the first-in-class treatment for erythropoietic protoporphyria (EPP), delivered as a subdermal implant.

Disclaimer

This entry is for educational purposes only and does not constitute medical advice. Dosing information reflects published regulatory or research data and is not a recommendation. Many compounds described here are not approved for human use in the United States. Consult a licensed medical professional before considering any peptide therapy.