Melanotan II vs PT-141 (Bremelanotide)
Melanotan II (Melanocortin receptor agonist) and PT-141 (Bremelanotide) (Melanocortin receptor agonist) are documented as co-studied in the PeptiDex library. This page puts the two entries side by side on class, molecular weight, half-life, origin, mechanism and studied research areas — every value taken from the entry it belongs to.
Why these two are co-studied
Cross-referenced for research context — not a usage or combination recommendation.
At a glance
| Attribute | Melanotan II | PT-141 (Bremelanotide) |
|---|---|---|
| Compound class | Melanocortin receptor agonist | Melanocortin receptor agonist |
| Research category | Cosmetic & Dermal | Hormonal & Sexual Health |
| Length (amino acids) | 7 amino acids | 7 amino acids |
| Molecular weight | ~1024 g/mol | ~1025 g/mol |
| Half-life | ~30-60 minutes (plasma, subcutaneous) | ~2.5 hours (subcutaneous) |
| Origin | Melanotan II is a synthetic cyclic analog of alpha-melanocyte-stimulating hormone (alpha-MSH), developed from melanocortin research at the University of Arizona. It is a distinct, non-selective compound from the linear Melanotan I. | PT-141 (bremelanotide) is a synthetic cyclic heptapeptide melanocortin agonist derived from the melanocortin peptide Melanotan II. It is marketed as Vyleesi. |
“Not documented” means the PeptiDex entry records no value for that field. Nothing on this page is estimated, and no figure is carried over from one compound to the other.
How Melanotan II works
Melanotan II is a cyclic heptapeptide that acts as a non-selective agonist across melanocortin receptors, including MC1R and MC4R. MC1R agonism on melanocytes stimulates melanogenesis and pigmentation, while MC4R agonism in the central nervous system is associated with effects on sexual arousal, which is the pharmacological basis linking it to the MC4R agonist bremelanotide (PT-141). Its cyclic, constrained structure contributes to potency and metabolic stability.
How PT-141 (Bremelanotide) works
PT-141 (bremelanotide) is a melanocortin receptor agonist with activity at MC4R (and other melanocortin receptors) in the central nervous system. Activation of MC4R in hypothalamic pathways is associated with modulation of sexual-response signaling, which is the mechanistic basis for its study and approved indication in sexual dysfunction. Unlike vasodilator-based therapies, it acts on central melanocortin pathways rather than peripheral vascular targets.
Mechanistic descriptions reflect published research-literature understanding and are quoted from each compound's own entry. Much peptide research is preclinical (in-vitro or animal-model); mechanism in humans may differ and is not established for many compounds.
Where each one appears in the literature
The research contexts each entry documents. Listing a research area is not a claim of efficacy or a therapeutic indication, and the two lists are not scored against each other.
Melanotan II
PT-141 (Bremelanotide)
What sets each apart
Melanotan II
Melanotan II is a cyclic, non-selective melanocortin agonist (MC1R and MC4R), distinguishing it from the linear, more MC1R-focused Melanotan I and from the MC4R-selective PT-141.
PT-141 (Bremelanotide)
PT-141 is an MC4R-focused, centrally acting approved drug (Vyleesi), distinguishing it from the non-selective tanning-oriented Melanotan II and from peripheral vasoactive agents.
Frequently asked questions
What is Melanotan II?
Melanotan II (MT-II) is a synthetic cyclic heptapeptide analog of alpha-melanocyte-stimulating hormone (alpha-MSH). It is a non-selective melanocortin receptor agonist studied in models of melanogenesis (pigmentation) and, via MC4R activity, sexual-response pathways. It is not an approved drug.
How does Melanotan II differ from Melanotan I?
Melanotan I (afamelanotide) is a linear 13-amino-acid alpha-MSH analog and is relatively MC1R-focused, while Melanotan II is a smaller cyclic heptapeptide that is broadly non-selective across melanocortin receptors. The broader receptor activity of MT-II is associated with additional effects such as libido changes and nausea seen in its research literature.
What is the reported half-life of Melanotan II?
Reported plasma half-life is short, on the order of roughly 30 minutes to about 1 hour after subcutaneous administration (some sources cite ~33 minutes). Importantly, pigmentation effects persist for days to weeks because melanocytes are stimulated to produce melanin, so the short plasma half-life does not reflect the duration of the observable effect.
What is PT-141 (bremelanotide)?
PT-141 (bremelanotide) is a synthetic cyclic 7-amino-acid melanocortin receptor agonist, a metabolite-derived analog of alpha-MSH. It preferentially activates the melanocortin-4 receptor (MC4R) in the central nervous system and is studied in the context of sexual arousal and desire pathways rather than acting on the vasculature.
Is PT-141 an FDA-approved drug?
Yes. Bremelanotide is FDA-approved (June 2019) under the brand name Vyleesi for the treatment of hypoactive sexual desire disorder (HSDD) in premenopausal women. It was the first approved as-needed injectable for HSDD. Research-chemical supply of the same molecule is a separate, non-pharmaceutical channel and is not the approved product.
How does PT-141 differ from PDE5 inhibitors like sildenafil?
PT-141 works centrally through MC4R activation in the hypothalamus to influence desire and arousal, whereas PDE5 inhibitors act peripherally on smooth-muscle blood flow. This is a fundamentally different mechanism, which is why it is studied in desire-focused rather than purely erectile models.
Answers are the ones published on each compound's own PeptiDex entry. They are educational summaries of research-literature context and are not medical advice.