A cyclic analog of alpha-MSH that promotes skin tanning, reduces appetite, and enhances sexual function.
Melanotan II (MT-II) is a synthetic cyclic analog of alpha-melanocyte-stimulating hormone (α-MSH) that was originally developed at the University of Arizona in the 1980s as a potential sunless tanning agent. It activates multiple melanocortin receptors (MC1R, MC3R, MC4R) with broad potency, producing a constellation of effects: increased melanin production (tanning without UV exposure), appetite suppression, enhanced sexual function and libido, and reduced body fat. Melanotan II is the precursor from which PT-141 (bremelanotide) was derived — PT-141 was developed to retain the sexual function benefits while reducing the tanning and other side effects. MT-II has a broader receptor profile than PT-141 and produces more pronounced tanning effects, but also has a higher side effect burden. It is not FDA-approved and is classified as a research chemical.
* Benefits based on preclinical/animal research unless otherwise noted.
FDA’s listing for Melanotan II cites published case reports of melanoma, posterior reversible encephalopathy syndrome, sympathomimetic toxidrome and priapism. DermNet additionally reports rhabdomyolysis and states that its use is not recommended for anybody. FDA placed Melanotan II in Category 2 (significant safety risks) in September 2023.
Melanotan II activates all five melanocortin receptor subtypes with varying potency, with highest affinity for MC1R, MC3R, and MC4R. MC1R activation on melanocytes triggers the cAMP-PKA pathway, stimulating the transcription factor MITF and upregulating the enzymes involved in melanin synthesis (tyrosinase, TRP-1, TRP-2). This produces eumelanin (brown/black pigment) in the skin, providing a tan and some degree of UV protection. MC3R and MC4R activation in the hypothalamus suppresses appetite through NPY/AgRP inhibition and POMC activation, and activates the neural circuits for sexual arousal (similar to PT-141). MC4R activation in the paraventricular nucleus also triggers spontaneous erections in men through a spinal cord mechanism. The broad receptor activation profile of MT-II compared to PT-141 explains its more pronounced tanning effects and higher incidence of nausea and other side effects.
Protocol Notes: Start with 0.25 mg to assess tolerance. Nausea is common, especially initially. Tanning effects begin within 1–2 weeks. Use sunscreen despite tanning — MT-II does not fully replace UV protection.
Add 2 mL bacteriostatic water to 10 mg vial → 5 mg/mL For 0.5 mg dose: draw 0.1 mL (10 units on U-100 syringe)
When sourcing Melanotan II for research purposes, the following quality benchmarks should be verified before use.
Lyophilized: refrigerate. Reconstituted: refrigerate and use within 30 days.
The statements made within this website have not been evaluated by the US Food and Drug Administration. The products and information provided are not intended to diagnose, treat, cure, or prevent any disease. This website is intended for educational and research purposes only. Many peptides described on this site are not approved by the FDA for human therapeutic use and are classified as research chemicals. Nothing on this site constitutes medical advice.
Moderate Evidence — Multiple animal studies and/or early human trials. Reasonable confidence in mechanism, but human data is limited.
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