Overview
Overview
PT-141 (bremelanotide) and Melanotan II are cyclic melanocortin receptor agonists with distinct but related applications. PT-141 is FDA-approved for hypoactive sexual desire disorder and is used on-demand[1][2], while Melanotan II has been studied for its effects on skin pigmentation and sexual function with daily dosing protocols[5][6]. This educational guide covers reconstitution, dosing, and administration for both peptides. Reconstitute each: Add 3.0 mL bacteriostatic water → ~3.33 mg/mL co
- Category
- Sexual Health
- Routes
- subcutaneous
Mechanism
PT-141
Mechanism of action
Mechanism of action
PT-141 increases sexual desire and arousal by acting on the brain. It is a cyclic heptapeptide that activates two of the five melanocortin receptors, MC3R and MC4R. These receptors are densely expressed in the hypothalamus, especially in the paraventricular nucleus (PVN), which is one of the brain's main control hubs for autonomic and reproductive function. When MC4R is activated in the PVN, it stimulates downstream oxytocin neurons that project to the spinal cord and influence sexual response. This is a centrally-initiated mechanism. PT-141 does not work by changing penile blood flow the way a PDE5 inhibitor like sildenafil does. That difference is why PT-141 affects desire, while sildenafil affects mechanical erectile function. PT-141 also has moderate affinity for MC1R (the pigmentation receptor) and negligible activity at MC2R (the cortisol-axis receptor) or MC5R. The MC1R activity is part of why darkening of the skin, gums, or breasts is listed as a possible adverse effect on the Vyleesi label. Cyclic heptapeptide agonist of MC3R and MC4R; moderate MC1R; negligible MC2R/MC5R. PVN MC4R activation → oxytocin release → spinal cord autonomic output influencing sexual response. Cyclic backbone and D-Phe7 substitution improve enzymatic stability versus linear MSH analogs.
Key research findings
- 01
PT-141 (bremelanotide) is a synthetic cyclic peptide melanocortin receptor agonist acting principally at MC3R/MC4R, derived from the non-selective parent compound Melanotan II (medicinal chemistry / preclinical).
- 02
Research describes its action as central, on melanocortin (MC4R) pathways associated with sexual arousal, mechanistically distinct from vascular agents such as PDE5 inhibitors (preclinical and human pharmacology).
- 03
Early human studies in the 2000s investigated intranasal and subcutaneous PT-141 for erectile response in men (human studies).
- 04
Two identically designed Phase 3 randomized, double-blind, placebo-controlled trials (RECONNECT) evaluated subcutaneous bremelanotide versus placebo in premenopausal women and reported statistically significant improvements in a sexual-desire score and a desire-related distress score (human studies; Kingsberg, Clayton et al., Obstetrics & Gynecology, 2019).
- 05
Across those trials, the most commonly reported observed effects in research were nausea, flushing, and headache (human study).
Primary source: Phase 3 (women, HSDD): RECONNECT trials, ~1,200 women, 1.75 mg SC on demand, 24 weeks. Significant gains in desire and reduction in distress vs placebo. Basis of FDA approval. Long-term safety (women, HSDD): 52-week open-label extension supported the on-demand 1.75 mg SC dose with no new safety signals. Phase 2 (men, ED, intranasal): Diamond 2006 reported pro-erectile effects of intranasal PT-141 in men with ED. Pharmaceutical development moved to injectable; intranasal route was not advanced to Phase 3. Phase 2 (women, arousal): Safarinejad 2008 and Clayton 2016 evaluated bremelanotide in female sexual dysfunction; informed the Phase 3 dose selection of 1.75 mg. Mechanism / preclinical: Pfaus 2004 in rats showed melanocortin agonism increases sexual solicitation behavior; consistent with the central mechanism via PVN MC4R.
Pharmacokinetic profile
Single-dose plasma curve over 24h. Shaded band = commonly-cited therapeutic window. Illustrative only.
Protocol Reference
Protocol reference
Commonly cited research range: 500–1500 mcg, daily.
Reference figures reported in the research literature — not a dosing recommendation. For interactive vial math and scheduling, see the Calculator and Schedule tabs.
Cited protocol & reconstitution guide
Source-backed reference fields by phase, including any volume fields authored in the cited guide.
Initial / Titration
500–750 mcg
Standard
1000–1500 mcg
Full / FDA-Approved
1750 mcg (1.75 mg)
| Phase | Reference amount | Units / volume |
|---|---|---|
| Initial / Titration | 500–750 mcg | 15–22 units (0.15–0.22 mL) |
| Standard | 1000–1500 mcg | 30–45 units (0.30–0.45 mL) |
| Full / FDA-Approved | 1750 mcg (1.75 mg) | 52 units (0.52 mL) |
Titration protocol
- DoseStart1.75 mg
Vyleesi label / Mayo Clinic drug summary
- RouteBuildSubcutaneous (abdomen or thigh)
Vyleesi label
- TimingBuild≥45 minutes before sexual activity
Vyleesi label
- Maximum frequencyBuild1 dose per 24 hours
Vyleesi label
- Maximum monthly useBuild8 doses per month
Vyleesi label
- Approved populationMaintenancePremenopausal women with HSDD
Vyleesi label
Storage & Handling
Storage requirements(typical for most peptides)
Can be stored for extended periods. Protect from moisture.
Store in refrigerator door. Never freeze after reconstitution.
Label vials with reconstitution date. Discard if cloudy.
Reconstitution steps
- 01🌡️Inspect the vial Check the label, lot number, and that the lyophilized cake or powder looks intact and uncolored.
- 02🧴Wipe the stopper Use a fresh alcohol swab on the stopper of both the BAC water vial and the PT-141 vial.
- 03💉Draw bacteriostatic water Pull the chosen volume of BAC water into a syringe (commonly 2 mL for a 10 mg vial).
- 04💧Add water slowly Inject the BAC water onto the inner wall of the PT-141 vial rather than directly onto the powder.
- 05🔄Swirl, do not shake Roll the vial gently between your palms until fully clear. Shaking can damage the peptide.
- 06🏷️Inspect the solution It should be clear and colorless. Do not use if cloudy or discolored.
- 07❄️Refrigerate Store reconstituted PT-141 at 36-46°F (2-8°C) and label the date.
Additional storage notes
-4°F (-20°C) long-term; refrigerator acceptable short-term — Use the supplier's stability data when available.
35.6-46.4°F (2-8°C) — Inspect each draw for clarity; discard if cloudy or discolored.
Room temperature, away from heat, moisture, and direct light; do not freeze — Per the FDA-approved label.
Clinical Evidence
Clinical evidence
Studied in clinical research on melanocortin-mediated sexual-response pathways and has undergone clinical development.
Phase 3 (women, HSDD): RECONNECT trials, ~1,200 women, 1.75 mg SC on demand, 24 weeks. Significant gains in desire and reduction in distress vs placebo. Basis of FDA approval. Long-term safety (women, HSDD): 52-week open-label extension supported the on-demand 1.75 mg SC dose with no new safety signals. Phase 2 (men, ED, intranasal): Diamond 2006 reported pro-erectile effects of intranasal PT-141 in men with ED. Pharmaceutical development moved to injectable; intranasal route was not advanced to Phase 3. Phase 2 (women, arousal): Safarinejad 2008 and Clayton 2016 evaluated bremelanotide in female sexual dysfunction; informed the Phase 3 dose selection of 1.75 mg. Mechanism / preclinical: Pfaus 2004 in rats showed melanocortin agonism increases sexual solicitation behavior; consistent with the central mechanism via PVN MC4R.
- 01PT-141 (bremelanotide) is a synthetic cyclic peptide melanocortin receptor agonist acting principally at MC3R/MC4R, derived from the non-selective parent compound Melanotan II (medicinal chemistry / preclinical).
- 02Research describes its action as central, on melanocortin (MC4R) pathways associated with sexual arousal, mechanistically distinct from vascular agents such as PDE5 inhibitors (preclinical and human pharmacology).
- 03Early human studies in the 2000s investigated intranasal and subcutaneous PT-141 for erectile response in men (human studies).
- 04Two identically designed Phase 3 randomized, double-blind, placebo-controlled trials (RECONNECT) evaluated subcutaneous bremelanotide versus placebo in premenopausal women and reported statistically significant improvements in a sexual-desire score and a desire-related distress score (human studies; Kingsberg, Clayton et al., Obstetrics & Gynecology, 2019).
- 05Across those trials, the most commonly reported observed effects in research were nausea, flushing, and headache (human study).
Evidence maturity varies by compound; much peptide research is preclinical (in vitro or animal-model). Where human data are limited, findings should be read as research observations, not clinical conclusions.
References
Literature references
Published research articles and sources related to PT-141.
- 01Mayo Clinic / Merative Micromedex Bremelanotide (subcutaneous route) — Description and Dosing. Mayo Clinic Drugs & Supplements (2026)et al. (2026)
- 02Kingsberg SA, Clayton AH, Portman D, et al. Bremelanotide for the Treatment of Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials. Obstetrics & Gynecology (2019)et al. (2019)
- 03Simon JA, Kingsberg SA, Portman D, et al. Long-Term Safety and Efficacy of Bremelanotide for Hypoactive Sexual Desire Disorder. Obstetrics & Gynecology (2019)et al. (2019)
- 04Clayton AH, Althof SE, Kingsberg S, et al. Bremelanotide for female sexual dysfunctions in premenopausal women: a randomized, placebo-controlled dose-finding trial. Women's Health (London) (2016)et al. (2016)
- 05Diamond LE, Earle DC, Rosen RC, Willett MS, Molinoff PB. Double-blind, placebo-controlled evaluation of the safety, pharmacokinetic properties and pharmacodynamic effects of intranasal PT-141, a melanocortin receptor agonist, in healthy males and patients with mild-to-moderate erectile dysfunction. International Journal of Impotence Research (2006)et al. (2006)
- 06Safarinejad MR. Evaluation of the safety and efficacy of bremelanotide, a melanocortin receptor agonist, in female subjects with arousal disorder: a double-blind placebo-controlled, fixed dose, randomized study. Journal of Sexual Medicine (2008)et al. (2008)
- 07Pfaus JG, Shadiack A, Van Soest T, Tse M, Molinoff P. Selective facilitation of sexual solicitation in the female rat by a melanocortin receptor agonist. Proceedings of the National Academy of Sciences USA (2004)et al. (2004)
- 08Simon JA, Kingsberg SA, Portman D, et al. Prespecified and Integrated Subgroup Analyses from the RECONNECT Phase 3 Studies of Bremelanotide. Journal of Women's Health (2022)et al. (2022)
- 09Pfaus J, Giuliano F, Gelez H. Bremelanotide: An overview of preclinical CNS effects on female sexual function. Journal of Sexual Medicine (2007)et al. (2007)
- 10Loti Labs (Editorial). PT-141 (Bremelanotide): Melanocortin Receptor Agonist Research Guide. Loti Labs Resources (2026)et al. (2026)
Observed Effects
Observed effects in cited research
Nausea
- Most common; reported in roughly 40% of bremelanotide users in Phase 3 trials. Usually mild and decreasing over time.
Flushing
- Common, especially in the first hour after dosing.
Headache
- Reported in a subset of users.
Injection site reactions
- Redness, soreness, or itching at the injection site is the most common local effect.
Transient blood pressure rise
- Typically a few mmHg systolic, peaking within hours and returning to baseline. The label contraindicates use in uncontrolled hypertension and CV disease.
Skin/gum/breast darkening
- Listed on the label, more likely with daily or near-daily use; tied to MC1R activity. Rare with the labeled on-demand schedule.
Theoretical and route-specific risks
- Intranasal PT-141 sold as a compounded product has not been evaluated in Phase 3 trials. Per-spray delivery varies with device, technique, and nasal congestion, which makes consistent dosing harder. Quality control for any non-FDA-approved peptide product is a separate risk and is one reason the Vyleesi label dose is anchored to a sealed autoinjector formulation.
Important
- PT-141 should not be combined with Melanotan II or other melanocortin agonists. The receptor overlap means safety effects can compound, and there is no clinical data supporting that combination.
Research Considerations
Research considerations
Research Use Only - not for human or veterinary therapeutic use. Has been studied in clinical research; on this platform it is handled strictly as a research material. Consult a licensed healthcare professional for any clinical decisions.
- Vyleesi is approved only for premenopausal women with acquired, generalized HSDD that is not better explained by a medical or psychiatric condition, relationship distress, or medication observed effects. The Vyleesi label states that postmenopausal women and men should not use it , and that it is not approved to enhance sexual performance. There is no FDA-approved PT-141 protocol for any other population.
- Women in the RECONNECT Phase 3 program self-administered 1.75 mg bremelanotide on demand and showed significant improvements in desire and reduced distress versus placebo over 24 weeks. The 1.75 mg dose was used regardless of body weight. The label does not advise weight-based dose adjustment. This is not a dosing recommendation.
- The Vyleesi label and the Mayo Clinic drug summary state that PT-141 should not be used in people with uncontrolled hypertension or known cardiovascular disease, because of the transient blood pressure rise after dosing. It is also not recommended during pregnancy or while planning pregnancy, and there is no adequate safety data for breastfeeding.
- Severe kidney or liver disease may slow clearance. Conditions that delay gastric emptying may worsen with PT-141 because melanocortin agonism slows gastric emptying. Naltrexone is listed as a notable interaction (PT-141 may reduce naltrexone exposure when both are used). PT-141 should not be combined with another melanocortin agonist such as Melanotan II, because the receptors overlap and the safety of combined exposure has not been studied.
Factors noted in the research literature; not patient-specific medical advice.
Regulatory Status
Regulatory status
RUO
Comparisons
Comparisons
| Compound | Mechanism | Route | Status |
|---|---|---|---|
| PT-141this | A cyclic heptapeptide melanocortin receptor agonist (MC3R/MC4R), an active metabolite of melanotan II, acting on central melanocortin pathways studied for modulation of sexual-response signaling. | subcutaneous | Investigational / RUO |
| Kisspeptin | A neuroendocrine peptide that activates KISS1R (GPR54) on GnRH neurons to stimulate gonadotropin-releasing hormone secretion, a key upstream regulator of the reproductive axis. | subcutaneous | Investigational / RUO |
| Melanotan II | A synthetic non-selective melanocortin receptor agonist (including MC1R and MC4R) studied for stimulation of melanogenesis (skin pigmentation) and central melanocortin-mediated activity. | subcutaneous | Investigational / RUO |
| Retatrutide | An investigational triple-receptor agonist targeting GLP-1, GIP, and glucagon receptors, combining appetite regulation, insulinotropic activity, and increased energy expenditure. | subcutaneous | Investigational / RUO |
| Selank | Modulates GABA and serotonin systems. Increases BDNF. Provides anxiolytic effects without sedation or cognitive impairment. | nasal, subcutaneous | Investigational / RUO |
| Semaglutide | Activates GLP-1 receptors to increase insulin secretion, slow gastric emptying, and reduce appetite through central mechanisms. | subcutaneous | Investigational / RUO |
| Semax | Increases BDNF expression, enhances dopamine and serotonin metabolism. Provides neuroprotection and cognitive enhancement. | nasal, subcutaneous | Investigational / RUO |
Attributes shown for research comparison only; not a statement of efficacy or therapeutic equivalence.
FAQ
Frequently asked questions
PT-141 is the research name for bremelanotide, a synthetic cyclic heptapeptide that activates melanocortin MC3R and MC4R receptors in the brain. It is FDA-approved as Vyleesi for premenopausal women with acquired, generalized hypoactive sexual desire disorder (HSDD). It is not the same kind of drug as sildenafil or tadalafil; it works centrally on desire rather than peripherally on blood flow.
The FDA-approved Vyleesi label lists 1.75 mg subcutaneous, given at least 45 minutes before sexual activity, with no more than one dose in 24 hours and no more than 8 doses per month. This is the only PT-141 protocol that has been evaluated in Phase 3 trials.
No. The FDA approval (Vyleesi) is specifically for premenopausal women with HSDD. The Vyleesi label states that men and postmenopausal women should not use it. Phase 2 evidence in men with erectile dysfunction exists (Diamond 2006, intranasal route), but pharmaceutical development did not advance that route to Phase 3.
No. The FDA-approved bremelanotide product is an injection (Vyleesi). Intranasal PT-141 was studied in Phase 2 but was never advanced to Phase 3 or approved. Compounded nasal sprays sold through some clinics are not FDA-approved formulations, and dose delivery varies by device and pharmacy.
The Vyleesi label and Phase 3 trial design use a ≥45-minute interval before sexual activity. Reported peak effects in trials fell roughly in the 1-3 hour window, with effects gradually tapering after that. Individual experience varies and trial timelines are not personal predictions.
Nausea is the most common adverse event, reported in about 40% of bremelanotide users in the Phase 3 RECONNECT trials at the 1.75 mg dose. Most cases were mild to moderate and decreased with repeat use. Other reported effects include flushing, headache, injection-site reactions, and a small transient increase in blood pressure. The label also warns about possible darkening of the skin, gums, or breasts, mainly with frequent use.
The Vyleesi label says PT-141 should not be used by people with uncontrolled hypertension or known cardiovascular disease, by men, by postmenopausal women, during pregnancy, or in pediatric patients. People taking naltrexone, or with severe kidney/liver disease or conditions affecting gastric emptying, should approach with extra caution and clinical input.
There is no formal clinical evidence combining PT-141 with PDE5 inhibitors. The mechanisms are different (central vs vascular), and the cardiovascular profiles differ as well. Any combination should involve a clinician, especially because PT-141 transiently raises blood pressure while PDE5 inhibitors lower it.
It should not. PT-141 and Melanotan II both act on the melanocortin receptor family, and combining two melanocortin agonists has not been studied for safety. Receptor overlap means observed effects can compound.
Vyleesi is sold as a pre-filled autoinjector and does not require reconstitution. For research-grade lyophilized vials, a 10 mg vial reconstituted with 2 mL of bacteriostatic water yields 5 mg/mL, which makes a 1.75 mg dose roughly 0.35 mL or 35 units on a U-100 insulin syringe. Use a fresh alcohol swab on the stopper, add water gently along the inner wall of the vial, swirl until clear, and refrigerate.
No. Peptide Dosing Protocols publishes label-derived and trial-derived protocol information for educational research purposes. We do not provide personal dosing recommendations. Personal use decisions should be made with a qualified clinician.
No. This page is an educational summary of the FDA-approved Vyleesi label and the published clinical trial evidence on bremelanotide (PT-141). It is not medical advice and is not a substitute for clinical consultation.
Research-use notice
Research Use Only. This educational content and calculation support is intended for private research documentation. It does not provide medical advice, human-use directions, or claims of safety or effectiveness.