Oxytocin vs PT-141 (Bremelanotide)
Oxytocin (Endogenous neurohormone (cyclic nonapeptide)) 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 | Oxytocin | PT-141 (Bremelanotide) |
|---|---|---|
| Compound class | Endogenous neurohormone (cyclic nonapeptide) | Melanocortin receptor agonist |
| Research category | Cognitive & Nootropic | Hormonal & Sexual Health |
| Length (amino acids) | 9 amino acids | 7 amino acids |
| Molecular weight | 1007.2 g/mol | ~1025 g/mol |
| Half-life | Approximately a few minutes in circulation | ~2.5 hours (subcutaneous) |
| Origin | Oxytocin is a naturally occurring nonapeptide hormone synthesized in the hypothalamus and released from the posterior pituitary. It was among the first peptide hormones to be sequenced and chemically synthesized (work by Vincent du Vigneaud). | 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 Oxytocin works
Oxytocin acts through the oxytocin receptor, a G-protein-coupled receptor, mediating uterine contraction and milk let-down in its classical endocrine roles. In the central nervous system it is studied as a neuromodulator involved in social bonding, trust, and stress regulation. Its cyclic structure includes an intramolecular disulfide bond and a C-terminal amide.
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.
Oxytocin
PT-141 (Bremelanotide)
What sets each apart
Oxytocin
Oxytocin is a naturally occurring, FDA-approved hormone, unlike the synthetic research peptides in this class; its behavioral/cognitive applications remain investigational.
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 oxytocin as a research peptide?
Oxytocin is a nine-amino-acid cyclic neuropeptide and hormone, with an intramolecular disulfide bridge between its two cysteine residues. In behavioral research it is studied for its roles in social bonding, trust, and stress modulation, and it is also a well-characterized endogenous hormone.
Why is intranasal oxytocin used in behavioral research?
Peripherally administered oxytocin crosses the blood-brain barrier poorly, so intranasal delivery is the standard route in social-cognition studies to promote nose-to-brain access. Its short plasma half-life of only a few minutes makes route of administration an important design factor.
How is oxytocin dosed in human research studies?
The most common intranasal research dose is 24 IU, often delivered as multiple sprays across both nostrils, with a typical range around 24-40 IU. One IU corresponds to roughly two micrograms of pure peptide, which is a useful conversion when interpreting protocols.
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.