PT-141 is the research designation for bremelanotide, an approved melanocortin agonist for one indication only.

The short version

PT-141 is another name for bremelanotide, a small synthetic peptide (a short chain of amino acids) that switches on certain receptors in the brain rather than acting on blood flow. In June 2019 the US FDA approved it for exactly one use: low sexual desire that causes real personal distress in women who have not yet reached menopause — a condition doctors call HSDD (hypoactive sexual desire disorder — persistent low sexual desire that causes genuine distress). Every other use you may have read about — in men, for erections, in older women — is off-label, meaning the approval does not cover it. The benefit in the approved group is real but modest, and the most common problem people report is nausea. This page summarizes what the published studies and the official label say. It is not medical advice.

What is PT-141?

PT-141 is the research designation for bremelanotide, a synthetic cyclic heptapeptide — a ring-shaped chain of seven amino acids — built as an analogue of alpha-MSH (alpha-melanocyte-stimulating hormone, a natural signaling molecule the body makes from a larger precursor protein) ^[1]. It activates melanocortin MC3R/MC4R receptors (think of these as brain switches that influence sexual desire, appetite, and skin pigment) concentrated in the hypothalamus and limbic system ^{[1] [6]}.

The regulatory story is the cleanest fact about this compound. In the RECONNECT Phase 3 trials — two identical randomized controlled studies, together enrolling 1,267 premenopausal women with HSDD — bremelanotide met both of its coprimary endpoints over 24 weeks ^[3]. On the strength of that record the FDA approved bremelanotide injection on June 21, 2019 (NDA 210557) for acquired, generalized HSDD in premenopausal women ^[11]. That sentence is the entire approved scope. It says nothing about men, nothing about erectile dysfunction, nothing about postmenopausal women, and nothing about general sexual performance. Those uses exist in the literature only as early-phase or investigational work, and this site treats them that way.

A note on what you may have bought. The finished, approved drug is a prescription product. Material sold online as a "PT-141 research chemical" is a laboratory reagent, not the approved medicine, and sits entirely outside the pharmaceutical framework that verifies a drug's identity, purity, and concentration ^[11].

PT-141 peptide: structure and identity

The molecule is a 1,025-dalton cyclic lactam heptapeptide with the sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH, closed by a bridge between the Asp and Lys side chains ^[1]. It is a structural relative of melanotan II, differing chiefly in that the C-terminal amide is replaced by a carboxylic acid. The ring matters: a cyclic peptide resists enzymatic breakdown better than a linear one, which is part of why bremelanotide survived development as an injectable drug when several linear melanocortin candidates did not.

For the record, the standard identifiers: molecular formula C50H68N14O10; CAS 189691-06-3; FDA UNII 6Y24O4F37N; DrugBank DB12420; INN bremelanotide. These are the same molecule under different filing systems — the research community's "PT-141," the regulator's "bremelanotide," the chemist's CAS number.

The identity question readers ask most is whether PT-141 and bremelanotide are the same thing. They are. Bremelanotide is simply the international nonproprietary name assigned to the molecule that investigators first labeled PT-141 ^[1]. One compound, two names, with the second carrying the weight of an approval the first never had on its own.

What does the PT-141 peptide do?

It works in the brain, not the bloodstream. Bremelanotide stimulates central melanocortin MC4R (and, secondarily, MC3R) receptors in hypothalamic and limbic circuits tied to sexual motivation — regions such as the medial preoptic area — and is thought to engage dopaminergic pathways governing desire ^{[1] [6]}. This is the line that separates it from the more familiar erectile-dysfunction drugs: PDE-5 inhibitors (for example, sildenafil and tadalafil) act peripherally on vascular smooth muscle to improve blood flow, while PT-141 acts centrally on the neural circuitry of desire and arousal ^[1].

The mechanistic evidence is unusually direct for a compound in this category. In a placebo-controlled crossover fMRI study of 31 premenopausal women with HSDD, MC4R agonism significantly increased sexual desire for up to 24 hours and altered how the brain processed erotic stimuli — enhancing amygdala-insula connectivity and cerebellar activity ^[5]. In female rats, the compound selectively increased appetitive, solicitational sexual behavior without affecting reflexive responses or general activity, marking it as the first pharmacological agent reported to act on appetitive female sexual behavior ^[2].

If you came here wanting the off-label male story, how PT-141 works covers the original erectile-dysfunction pharmacology — early, investigational, and never approved — alongside the female evidence that carried the drug to market.

The honest summary of the evidence

Three things are true at once, and the editorial job is to hold all three.

First, the effect is real. Both RECONNECT trials met their coprimary endpoints with statistical significance, and a 52-week open-label extension found the benefit sustained with no new safety signals ^{[3] [4]}. Second, the effect is modest. The integrated improvement in the FSFI desire score was +0.35 over placebo, and the reduction in desire-related distress (FSDS-DAO item 13) was -0.33 — both significant, both small, and independent re-analyses have argued the clinical meaningfulness is limited ^[3]. (FSFI and FSDS are the standard validated questionnaires trials use to score sexual desire and the distress low desire causes.) Third, tolerability is the real-world ceiling. Nausea affected roughly 40% of women over long-term use and was the leading reason participants discontinued ^[4].

The full ledger lives on PT-141 side effects: the cited adverse-event profile from the trials and the label, the transient cardiovascular signal, the hyperpigmentation, and — kept clearly to one side — the unverified community reports. For the approved-use story in depth, see PT-141 for women. Short, direct answers sit in the frequently asked questions about PT-141, and every number on the site traces back to the cited studies and references. This page is the overview; the rest of the site is the argument staged in full.