PT-141 vs Melanotan II

Hormone

Cosmetic

FDA Approved

Research Only

Bremelanotide is a non-selective melanocortin receptor agonist (potency order MC1R > MC4R > MC3R > MC5R > MC2R per the FDA label). The sexual response is driven by central MC4R activation in the medial preoptic area and paraventricular nucleus of the hypothalamus, modulating dopaminergic and oxytocinergic pathways that mediate arousal — a mechanism independent of the vasodilatory PDE5-inhibitor pathway.

MT-II is a non-selective agonist at all four peripheral melanocortin receptors — MC1R (melanocyte pigmentation), MC3R and MC4R (energy balance and central sexual arousal), and MC5R (exocrine gland function). MC1R activation on melanocytes increases cAMP → PKA → MITF → tyrosinase, driving eumelanin synthesis; UV exposure is generally required to produce visible tanning. MC4R activation in the hypothalamus mediates the prominent sexual arousal and spontaneous erection side effects seen in the original Phase I trials — this observation was the basis for developing the selective C-terminal analog bremelanotide (PT-141, Vyleesi) for female HSDD.

1.75 mg

500–1000 mcg

SubQ

SubQ

As needed, at least 45 minutes before anticipated sexual activity

Daily during loading (2–3 weeks), then 2–3 times per week for maintenance

FDA-approved dose is 1.75 mg SubQ (abdomen or thigh) via autoinjector. No more than one dose per 24 hours and no more than 8 doses per month. Discontinue if no benefit after 8 weeks. Patients should be screened for cardiovascular disease and have blood pressure controlled before use; alcohol should be avoided around dosing. Not a chronic therapy.

Grey-market protocols typically use 0.5–1 mg SubQ daily during a 2–3 week loading phase until desired pigmentation is reached, followed by 2–3 weekly maintenance doses. UV exposure is generally required for visible tanning. Not FDA-approved anywhere, explicitly warned against by the UK MHRA and other regulators, and sold only as an unregulated research chemical with no guarantee of identity or purity. Skin self-examination and dermatologic surveillance are advisable given documented nevus changes.