PT-141 10mg

PT-141 is a synthetic cyclic heptapeptide. Its generic name is bremelanotide, and it belongs to the melanocortin receptor agonist class. The molecule was developed from the melanocortin pharmacophore shared by the natural hormone alpha-melanocyte-stimulating hormone, retaining the His-Phe-Arg-Trp core that drives melanocortin receptor binding. PT-141 is the active downstream form of the earlier research peptide Melanotan II, with the C-terminal amide removed and the ring cyclised.

The structure is closed into a ring through a side-chain lactam bridge, and it incorporates a D-phenylalanine residue. Both features matter for stability. The cyclic backbone and the D-amino acid raise resistance to enzymatic breakdown — relative to a comparable linear peptide — and they sharpen the molecule's receptor selectivity. PT-141 acts as a non-selective agonist across several melanocortin receptors, with the central MC4R and MC3R activity being the focus of most published research.

The compound is supplied as a lyophilized — freeze-dried — white-to-off-white powder in a sealed amber-glass vial. Each vial contains 10 mg of peptide. Reconstitution with bacteriostatic water is required before the peptide can be drawn into an insulin syringe. Reconstitution mechanics are covered in the Reconstitution accordion.

PT-141 carries an unusually well-developed clinical literature for a research peptide. It progressed through a full drug-development program, including the two Phase 3 RECONNECT trials in premenopausal women with hypoactive sexual desire disorder (PMID 31599840), a long-term safety and efficacy extension (PMID 31599847), and pooled safety analyses across the program (PMID 35147466). The branded compound was approved by the United States FDA in 2019 (PMID 31893927).

That clinical record is not uniformly positive, and the honest research picture includes critical appraisal. A 2024 review examined the effect sizes reported in the pivotal trials and questioned their clinical meaningfulness (PMID 36809187). Blood-pressure pharmacodynamics tied to melanocortin agonism have also been characterised in dedicated ambulatory-monitoring work (PMID 27977473). Researchers reviewing PT-141 should weigh the regulatory milestone against these measured assessments.

No regulatory authority has cleared PT-141 as a research reagent for therapeutic use in humans or animals; the FDA approval applies to a specific branded pharmaceutical, not to research-grade material. Ronin Peptides ships the compound exclusively as a research-grade reagent for benchwork. Dosing protocols, treatment regimens, and administration instructions are out of scope and are not provided in any form.

PT-141 acts as an agonist at melanocortin receptors. It binds the same receptor family engaged by the endogenous melanocortin peptides, sharing their His-Phe-Arg-Trp recognition motif. The receptors of primary research interest are the centrally expressed melanocortin-4 receptor (MC4R) and melanocortin-3 receptor (MC3R) — the molecule also shows activity at MC1R. An early overview from the originating research group framed PT-141 as a melanocortin agonist acting through this pathway (PMID 12851303).

The mechanism studied in the sexual-function literature is central rather than peripheral. Unlike phosphodiesterase-5 inhibitors, which act on peripheral vascular smooth muscle through the nitric oxide pathway, PT-141 is proposed to act upstream in hypothalamic and limbic melanocortin circuits. A rodent-model study reported selective facilitation of sexual solicitation behaviour following melanocortin receptor activation, consistent with a central site of action (PMID 15226502). This central-versus-peripheral distinction is the recurring theme across the PT-141 mechanism literature.

Structural-biology work has clarified how ligands recognise and activate MC4R. A 2021 cryo-electron-microscopy study resolved the receptor in its active state and detailed the binding pocket and activation conformation (PMID 34433901). A 2023 review of the central melanocortin system placed MC4R signalling in its broader physiological context, spanning energy balance and downstream neural circuits beyond the sexual-function endpoint (PMID 37365323).

One pharmacodynamic feature has direct safety relevance. Melanocortin agonism produces transient increases in blood pressure, which were quantified in an ambulatory blood-pressure monitoring study across the development program (PMID 27977473). This effect, rather than the receptor-binding profile alone, shaped the clinical-use restrictions documented in the regulatory and safety literature.

The largest body of clinical research on PT-141 covers hypoactive sexual desire disorder in premenopausal women. The pivotal evidence comes from the two Phase 3 RECONNECT trials — which measured change on validated desire and distress endpoints against placebo (PMID 31599840). A long-term open-label extension followed responders to characterise durability and safety over an extended period (PMID 31599847), and an accompanying editorial situated the program within the wider field of female sexual-function research (PMID 31599837).

The Phase 3 program was built on earlier dose-finding work. A randomised placebo-controlled dose-finding trial in premenopausal women examined the dose-response relationship (PMID 27181790), and a Phase 2b responder analysis informed the dose selected for the pivotal studies (PMID 31277966). Integrated and prespecified subgroup analyses from RECONNECT later examined consistency of the measured effect across patient subgroups (PMID 35230162).

The earliest clinical research predates the female-HSDD focus. A 2004 study evaluated the safety, pharmacokinetics, and pharmacodynamics of subcutaneous PT-141 in healthy male subjects and in men with an inadequate response to a phosphodiesterase-5 inhibitor (PMID 14999221). A 2006 study reported effects on the subjective sexual response in premenopausal women with arousal disorder (PMID 16839319), and a separate randomised trial examined the compound in men who had not responded to sildenafil (PMID 18206919).

Safety has been characterised in dedicated work. A Phase 1 study assessed tolerability when PT-141 was coadministered with ethanol (PMID 28189361), and a pooled safety analysis compiled adverse-event data across the entire clinical development program (PMID 35147466). The most commonly reported effects in these analyses were nausea, flushing, and headache — alongside the transient blood-pressure changes noted in the mechanism section.

Critical appraisal forms an important part of the honest research record. A 2023 evaluation weighed the benefits and limitations of bremelanotide injection in a balanced drug-assessment format (PMID 36242769), and a 2024 review argued that the effect sizes observed in the pivotal trials were small and questioned their clinical meaningfulness (PMID 36809187). Researchers planning new work should review both the favourable regulatory record and these measured critiques before designing protocols.

Unopened lyophilized vials hold up well under dry ambient storage; usable activity persists for several weeks even without refrigeration. The recommended container is the unopened original vial — keep the seal intact until reconstitution. Refrigeration at 2–8 °C is appropriate once the working timeline extends past a month. A standard freezer at −20 °C handles archival storage; ultra-low storage at −80 °C is rarely needed for typical bench-research timescales.

Keep vials shielded from light, ideally in their original outer packaging. Repeated temperature cycling accelerates degradation noticeably more than steady storage at any single temperature inside the recommended bands — minimise transitions between cold and ambient.

After reconstitution, refrigerate the solution at 2–8 °C without delay. The typical working window for a reconstituted preparation is four to six weeks at fridge temperature. Past that window, peptide concentration drifts downward through chemical degradation pathways even though the bacteriostatic water's benzyl alcohol still suppresses microbial growth. The 0.9% benzyl alcohol holds back bacterial contamination — the dominant spoilage path — but does not arrest the slower hydrolysis, oxidation, and aggregation processes that accumulate in any aqueous peptide solution.

When a research timeline extends past six weeks, common practice is splitting the reconstituted solution into single-use volumes and freezing them at −20 °C immediately. Ice-crystal formation during each freeze-thaw cycle inflicts mechanical damage on peptide chains, and pre-splitting eliminates the cumulative loss that comes from thawing one vial multiple times. Thaw individual aliquots overnight in a refrigerator — never at room temperature — and use them within a few days of thaw.

The reconstituted compound should be visually clear and colourless. Discard any vial showing turbidity, suspended particulate, yellowing, or visible precipitate. The diluent of choice is USP-grade bacteriostatic water containing 0.9% benzyl alcohol — see the bacteriostatic water listing for reconstitution-grade water.

PT-141 occupies a mechanistic niche of its own in the Ronin catalog: it is the only melanocortin receptor agonist in the library. The table below contrasts it with other CNS-active and signaling peptides by mechanism class. The comparison is structural only — these compounds are studied in different research domains and are not interchangeable.

For researchers exploring CNS-active peptides more broadly, the compound library groups the catalog by research domain. PT-141 sits within the signaling and CNS-active grouping rather than the recovery or metabolic categories.

A 10 mg vial of PT-141 reconstituted with 2 mL of bacteriostatic water yields a final concentration of 5 mg/mL, or 5,000 mcg/mL. Other diluent volumes scale linearly: 1 mL gives 10 mg/mL, 5 mL gives 2 mg/mL.

Reconstitution procedure:

1. Bring both vials — peptide and bacteriostatic water — to room temperature before opening.
2. Sanitise both rubber stoppers with an alcohol swab.
3. Pull the chosen diluent volume into a sterile transfer syringe.
4. Direct the water against the inner wall of the peptide vial as it is injected — never onto the lyophilized cake, since direct impact foams the solution and denatures peptide at the air-water interface.
5. Invert slowly or swirl gently until everything dissolves. Do not vortex; do not shake.
6. Refrigerate at 2–8 °C the moment reconstitution completes.

A finished preparation should be visually transparent with no suspended particulate. If the solution is hazy or contains visible material, treat it as degraded or contaminated and discard.

For dose-volume calculations on insulin syringes, use the Ronin peptide reconstitution calculator. The calculator converts target volumes to U-100 syringe units automatically.

In published clinical research, PT-141 was administered subcutaneously, and the pivotal trials used a fixed per-occasion amount taken on an as-needed basis ahead of anticipated activity (PMID 31599840, PMID 31277966). The early pharmacokinetic work characterised subcutaneous absorption and a plasma half-life in the range of roughly two to four hours (PMID 14999221). These figures are research-reference only — Ronin Peptides does not provide dosing recommendations or administration instructions for any non-laboratory purpose.

1. Molinoff PB et al. PT-141: a melanocortin agonist for the treatment of sexual dysfunction. Ann N Y Acad Sci. 2003;994:96-102. PMID: 12851303
2. Rosen RC et al. Evaluation of the safety, pharmacokinetics and pharmacodynamic effects of subcutaneously administered PT-141, a melanocortin receptor agonist, in healthy male subjects and in patients with an inadequate response to Viagra. Int J Impot Res. 2004;16(2):135-142. PMID: 14999221
3. Pfaus JG et al. Selective facilitation of sexual solicitation in the female rat by a melanocortin receptor agonist. Proc Natl Acad Sci U S A. 2004;101(27):10201-10204. PMID: 15226502
4. Diamond LE et al. An effect on the subjective sexual response in premenopausal women with sexual arousal disorder by bremelanotide (PT-141), a melanocortin receptor agonist. J Sex Med. 2006;3(4):628-638. PMID: 16839319
5. Safarinejad MR et al. Salvage of sildenafil failures with bremelanotide: a randomized, double-blind, placebo controlled study. J Urol. 2008;179(3):1066-1071. PMID: 18206919
6. Clayton AH et al. Bremelanotide for female sexual dysfunctions in premenopausal women: a randomized, placebo-controlled dose-finding trial. Womens Health (Lond). 2016;12(3):325-337. PMID: 27181790
7. White WB et al. Usefulness of ambulatory blood pressure monitoring to assess the melanocortin receptor agonist bremelanotide. J Hypertens. 2017;35(4):761-768. PMID: 27977473
8. Clayton AH et al. Phase 1 Randomized Placebo-controlled, Double-blind Study of the Safety and Tolerability of Bremelanotide Coadministered With Ethanol in Healthy Male and Female Participants. Clin Ther. 2017;39(3):514-526. PMID: 28189361
9. Althof S et al. Responder Analyses from a Phase 2b Dose-Ranging Study of Bremelanotide. J Sex Med. 2019;16(8):1226-1235. PMID: 31277966
10. Kingsberg SA et al. Bremelanotide for the Treatment of Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials. Obstet Gynecol. 2019;134(5):899-908. PMID: 31599840
11. Simon JA et al. Long-Term Safety and Efficacy of Bremelanotide for Hypoactive Sexual Desire Disorder. Obstet Gynecol. 2019;134(5):909-917. PMID: 31599847
12. Carson SA et al. Boosting Female Sexual Response by RECONNECTing the Dots. Obstet Gynecol. 2019;134(5):897-898. PMID: 31599837
13. Mayer D et al. Bremelanotide: New Drug Approved for Treating Hypoactive Sexual Desire Disorder. Ann Pharmacother. 2020;54(7):684-690. PMID: 31893927
14. Zhang H et al. Structural insights into ligand recognition and activation of the melanocortin-4 receptor. Cell Res. 2021;31(11):1163-1175. PMID: 34433901
15. Clayton AH et al. Safety Profile of Bremelanotide Across the Clinical Development Program. J Womens Health (Larchmt). 2022;31(2):171-181. PMID: 35147466
16. Simon JA et al. Prespecified and Integrated Subgroup Analyses from the RECONNECT Phase 3 Studies of Bremelanotide. J Womens Health (Larchmt). 2022;31(3):391-400. PMID: 35230162
17. Sweeney P et al. Targeting the central melanocortin system for the treatment of metabolic disorders. Nat Rev Endocrinol. 2023;19(9):507-519. PMID: 37365323
18. Cipriani S et al. An evaluation of bremelanotide injection for the treatment of hypoactive sexual desire disorder. Expert Opin Pharmacother. 2023;24(1):27-34. PMID: 36242769
19. Spielmans GI et al. Small Effects, Questionable Outcomes: Bremelanotide for Hypoactive Sexual Desire Disorder. J Sex Res. 2024;61(4):507-520. PMID: 36809187