Research digest · Melanocortin MC4R agonist
PT-141 is bremelanotide — approved for exactly one use, and studied across the melanocortin literature.
A raw, honestly-labelled reading of what the trials measured: the one FDA-approved indication, the off-label male research, the modest effect size, and the tolerability cost that comes with it.
The short version
PT-141 (also called bremelanotide) is a real, FDA-approved prescription drug — but its approval covers a single use: low sexual desire that causes genuine distress in premenopausal women, a condition doctors call HSDD (hypoactive sexual desire disorder — persistent low sexual desire that causes real personal distress) [3]. It works on the brain, not on blood flow: it switches on melanocortin MC3R/MC4R receptors (brain switches that influence sexual desire, appetite, and skin pigment) [1]. The benefit in trials was real but small, and it came with a clear cost — about 40% of long-term users felt nauseated [4]. This page is the plain-English map; the cited detail follows.
What is PT-141?
PT-141 is the research designation for bremelanotide, a synthetic cyclic heptapeptide (a ring of seven amino acids) modelled on the natural hormone alpha-MSH [1]. Its molecular formula is C50H68N14O10; the sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH and the lab identifier is CAS 189691-06-3. The compound activates melanocortin receptors in the brain — chiefly MC4R — to influence sexual desire and arousal [1]. In June 2019 the US FDA approved bremelanotide injection (NDA 210557) for one indication: acquired, generalized HSDD in premenopausal women [6]. Everything else — use in men, for erectile dysfunction, in postmenopausal women, for general sexual "performance" — is off-label and is not what the approval supports. Material sold online as a "PT-141 research chemical" is laboratory material only; it is not the approved finished drug, and no agency oversees its identity, purity, or concentration.
PT-141 peptide: a synthetic melanocortin agonist
The PT-141 peptide is a melanocortin receptor agonist — a compound that switches on the receptors that normally respond to alpha-MSH. It is a seven-amino-acid ring closed by a lactam bridge, structurally related to alpha-MSH and to the related peptide melanotan II, with a molecular weight of 1025.2 Da [1]. Its cyclic structure makes it more stable than a linear peptide. "Bremelanotide" and "PT-141" name the same molecule: bremelanotide is the international nonproprietary name (INN); PT-141 is the older research code [6]. The drug class matters because it explains both the benefit and the side effects — MC4R sits in brain circuits that govern desire and appetite, and a related receptor (MC1R) in the skin explains the pigment changes reported with repeated dosing [1].
What is PT-141 used for?
PT-141 (bremelanotide) is FDA-approved as a subcutaneous injection (one given just under the skin) for a single use: acquired, generalized HSDD in premenopausal women [3][6]. "Acquired" means the low desire developed after a period of normal function; "generalized" means it is not limited to a specific partner or situation. That is the entire approved indication. Use in men, off-label and investigational — and use in postmenopausal women — is not supported by the approval. The case for the approved use rests on two large trials called RECONNECT and a 52-week follow-up; the RECONNECT clinical-trial results are the core of the human evidence, and they are real but modest [3][4]. For the female-specific picture, see PT-141 for women and HSDD; for the honest cost, see PT-141 side effects.
The honest cost, printed up front
This site leads with the tolerability cost rather than burying it. In the 52-week extension study, the most common drug-related events were nausea (40.4%), flushing (20.6%), and headache (12.0%); nausea was the leading reason participants stopped [4]. The label warns of a transient rise in blood pressure with a drop in heart rate, and lists a contraindication: it is not for people with uncontrolled high blood pressure or known cardiovascular disease [6]. Repeated frequent dosing can darken the skin, gums, and other tissue [4]. And the benefit it buys is statistically real but clinically modest — independent re-analyses have argued the effect is small. The full PT-141 dosage and half-life figures and the complete tolerability ledger are set out on their own pages, cited line by line.