Melanotan II is a synthetic analog of α-melanocyte-stimulating hormone (α-MSH).
Mechanism: Binds melanocortin receptors (MC1R, MC3R, MC4R, MC5R), triggering melanin production for skin pigmentation. Via MC4R, it also affects sexual arousal and appetite. The basis on which PT-141 (MC4R-selective) was developed.
Use case: Dermal tanning without UV exposure. Subcutaneous injection, dose-titrated. Side benefit (or side effect, depending on context): consistent libido and sexual response effects.
Caveats: Nausea on initial doses, darkening of moles and freckles, occasional persistent erections. Photograph existing moles before starting; monitor for changes. Not regulated; quality varies dramatically.