Melanotan II

A cyclic analogue of alpha-MSH (melanocyte-stimulating hormone) that non-selectively activates multiple melanocortin receptors: MC1R (skin pigmentation), MC3R (energy balance, libido), MC4R (sexual function, appetite suppression), and MC5R (exocrine gland function). The simultaneous activation of multiple receptors produces several simultaneous effects: increased melanin production in skin (tanning without UV), penile erection and libido enhancement (MC4R in the hypothalamus and spinal cord), and appetite suppression. The non-selectivity that produces these multiple effects is also responsible for its significant side effect profile — activating melanocortin receptors systemically rather than at targeted sites produces effects across multiple organ systems simultaneously.

Developed at the University of Arizona in the 1980s as part of a cancer prevention research program targeting UV-independent tanning. Phase I and Phase II trials were conducted at the University of Arizona demonstrating tanning efficacy and sexual function improvement. Further clinical development was abandoned due to the side effect profile and regulatory complexity. PT-141 (Bremelanotide) was subsequently developed as a selective MC4R agonist without the tanning side effects, and has achieved FDA approval. Melanotan II remains without regulatory approval anywhere in the world. ProtocolHub recommends PT-141 over Melanotan II for sexual function applications given PT-141's superior safety profile and FDA-approved status.

Loading phase then maintenance as needed — not for continuous daily use