Melanotan II

A cyclic heptapeptide and nonselective melanocortin receptor agonist originally developed at the University of Arizona in the 1990s. Melanotan II activates MC1R through MC5R simultaneously, producing skin tanning (MC1R), sexual arousal (MC4R), and appetite suppression (MC3R/MC4R). Clinical development was halted due to safety concerns, and the compound is not approved for human use in any jurisdiction.

It is widely discussed in biohacking and bodybuilding communities for cosmetic tanning and libido effects. Regulatory agencies including the FDA, Health Canada, TGA, and EMA have issued explicit warnings against its use. PT-141 (bremelanotide), the FDA-approved HSDD drug, is a metabolite of Melanotan II.

A pilot phase I study (Dorr et al., 1996) evaluated subcutaneous doses of 0.01-0.03 mg/kg in healthy volunteers, demonstrating dose-dependent tanning and nausea. Wessells et al. (2000) documented penile erection effects in a small human study. Clinical development was discontinued due to the compound's nonselective receptor profile and associated safety signals.

A 2021 qualitative study of online discussion forums (Evans-Brown et al.) documented widespread community use with self-reported side effects and harm-reduction practices. Case reports have documented serious adverse events including rhabdomyolysis with CPK levels exceeding 17,000 IU/L. No controlled efficacy trials have been completed for any indication.

Community-reported dosing protocols are extrapolated from early phase I data and are not clinically validated.