PT-141 is the research designation for bremelanotide, a central melanocortin agonist studied for sexual desire.

The short version

PT-141 is another name for bremelanotide, a small synthetic peptide that works in the brain. It switches on melanocortin MC3R/MC4R receptors (brain switches that influence sexual desire, appetite and skin pigment) rather than acting on blood vessels. In 2019 it became an FDA-approved injection for one specific problem: HSDD (hypoactive sexual desire disorder — persistent low sexual desire that causes real personal distress) in women who have not reached menopause. Every other use — in men, for erectile difficulty, after menopause, or for "enhancement" — is off-label and rests on early data only. This site summarizes what the studies and the drug label actually report. It is not medical advice and recommends no dose for anyone.

PT-141 (the bremelanotide peptide), in plain terms

PT-141 is the research-program designation for bremelanotide, a synthetic cyclic heptapeptide (a chain of seven amino acids joined into a ring, which makes it more stable than a straight chain) modeled on alpha-MSH, a natural melanocortin hormone the body makes from a precursor protein called POMC ^[1]. The PT-141 peptide acts centrally, on melanocortin receptors concentrated in the hypothalamus and limbic system — the brain's desire and motivation circuitry — chiefly the melanocortin 4 receptor (MC4R), with secondary activity at MC3R ^[1]. That is the mechanistic line that separates it from the more familiar erectile-dysfunction drugs: those work on blood flow in the periphery; PT-141 works on the neural signals of wanting ^[1].

The molecule is documented in detail. Bremelanotide is the international nonproprietary name (INN); its CAS number is 189691-06-3, its molecular weight is 1025.2 Da, and its sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH ^[6]. Structurally it is a close relative of an older melanocortin peptide, with the C-terminal amide replaced by a carboxylic acid — a change that shifts the molecule toward the central desire effect rather than skin pigmentation ^[1]. Material sold as "PT-141 research chemical" is laboratory material — it is not the approved finished drug product, exists outside the pharmaceutical approval framework with no oversight of identity or purity, and nothing here is a protocol for using it.

The one approved use, and the modest size of the effect

Bremelanotide's single FDA approval (June 21, 2019, NDA 210557) covers acquired, generalized HSDD in premenopausal women ^[6]. That approval rests on two identical Phase 3 randomized controlled trials known as RECONNECT (n=1267), in which a 1.75 mg as-needed subcutaneous (injected just under the skin) dose met both coprimary endpoints: sexual desire rose and desire-related distress fell versus placebo over 24 weeks ^[3].

The honest framing is that the effect is statistically real but clinically modest. On the integrated FSFI (Female Sexual Function Index) desire score the improvement over placebo was +0.35, and on the FSDS-DAO item-13 distress score it was -0.33 ^[3] — FSFI and FSDS being the standard questionnaires trials use to score sexual desire and the distress that low desire causes. Independent re-analyses have argued these effects, while significant, are small and have questioned how meaningful they are in daily life. We surface that debate rather than bury it. The full story on PT-141 for women (HSDD) sits alongside the RECONNECT Phase 3 trials for the efficacy picture and PT-141 side effects for the tolerability record.

Brain, not blood flow — and a clearly bounded record

What PT-141 does is best understood as central, not vascular. In rats and nonhuman primates, systemic bremelanotide produced erectile responses and activated hypothalamic neurons; in early studies it produced dose-dependent erectile activity in men with erectile dysfunction ^[1]. In female rats it selectively increased solicitational (desire-driven) sexual behavior without changing reflexive behaviors or general movement — the first reported agent to act on appetitive female sexual behavior ^[2]. A 2022 functional-MRI study in 31 premenopausal women with HSDD showed MC4R agonism increased desire for up to 24 hours and altered how the brain processed erotic stimuli ^[5].

That is a genuinely characterized molecule with a genuinely bounded label. The boundary matters: see how PT-141 works for the mechanism, off-label male and erectile research for the investigational side, and common questions about PT-141 for the rest. Whether is PT-141 FDA-approved has a precise answer — yes, for one indication — and the studies and references behind every figure on this site are listed in full.

Off-label, investigational, and the honest tolerability ledger

Everything beyond HSDD in premenopausal women is off-label or still in development. Use in men is off-label; the male erectile evidence is early-phase, including a discontinued intranasal program and, in 2024, a newly initiated Phase 2 study pairing bremelanotide with a PDE-5 inhibitor in men who do not respond to those inhibitors alone ^[1][14]. There is no approval for postmenopausal women, for erectile dysfunction, or for sexual "enhancement." An off-label thread around weight also exists because the same MC4R receptor sits in appetite circuits — two Phase 1 trials in obese women found high-frequency dosing lowered body weight by about 1.3 kg over 16 days — but that is a pharmacology observation, not a use ^[7].

The tolerability ledger is part of the honest picture, not a footnote. In long-term use the most common adverse events were nausea (40.4%), flushing (20.6%), and headache (12.0%), with nausea the leading reason participants discontinued ^[4]. The label also records a transient rise in blood pressure and contraindicates the drug in uncontrolled hypertension or known cardiovascular disease ^[6]. We keep that record front and center — see PT-141 side effects — because a digest of an approved medication owes readers the burdens alongside the benefit.