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PrecisePep/Peptide Library/PT-141
Aesthetic & Melanocortin
bremelanotide · Vyleesi® · MT-2 metabolite
The melanotan metabolite that became an approved drug — a centrally acting melanocortin agonist for sexual desire, working on the brain rather than on blood flow.
PT-141 is what happens when a side effect becomes the drug. It is bremelanotide, a metabolite of melanotan-2, and it was developed specifically for the erectile and desire effects that made the parent compound problematic as a tanning agent. It is approved by the FDA as Vyleesi for acquired, generalised hypoactive sexual desire disorder in premenopausal women.[1]
Its mechanism is what distinguishes it. PDE5 inhibitors such as sildenafil act on vascular smooth muscle — they enable an erection given arousal. PT-141 acts on melanocortin receptors in the central nervous system and affects desire. Those are different problems, and the compound works for people the vascular drugs do not help.[2]
It was also studied extensively in male erectile dysfunction. An intranasal formulation was discontinued during development over blood-pressure increases; the subcutaneous route and the female HSDD indication is where it reached approval. Male use is off-label everywhere.
Vyleesi is approved for premenopausal women with acquired, generalised HSDD — not for men, not for postmenopausal women, and not for general libido enhancement. It also carries explicit dose limits (one per 24 hours, eight per month) that community use routinely exceeds.
Central MC4R agonism. Activation of melanocortin-4 receptors in hypothalamic and limbic circuitry increases sexual desire and arousal. This is upstream of the vascular events a PDE5 inhibitor addresses.
Dopaminergic involvement. Melanocortin signalling in the medial preoptic area modulates dopamine release, which is the proposed link between receptor activation and the subjective experience of desire.
Non-vascular. Because it does not act on smooth muscle, it does not require intact vascular function and can be effective where PDE5 inhibitors are not — and it does not carry the nitrate interaction that defines PDE5 safety.
Residual non-selectivity. Bremelanotide is more MC4R-weighted than melanotan-2 but is not fully selective. Some pigmentation effects, nausea and flushing persist — they are the same receptor family producing the same familiar effects.
Blood pressure. Melanocortin agonism produces a transient rise in blood pressure and fall in heart rate after dosing. This is labelled, dose-related, and the reason the intranasal programme was stopped.
Effects that have been reported. A study-tier entry means a result was published — not that the effect is established, reproducible, or transferable from a rodent to a person.
Highest confidenceReported in peer-reviewed literature, registered clinical trials, or regulatory filings. Note the model: much peptide literature is in vitro or rodent work, not human trial data.
Two phase 3 randomised placebo-controlled trials in premenopausal women with acquired generalised HSDD demonstrated statistically significant improvements in desire and reduced distress, supporting approval.
Earlier human trials demonstrated erectile responses in men, including in those with an inadequate response to PDE5 inhibitors — the finding that established the central mechanism as clinically real.
Central rather than vascular, which is why it can help where sildenafil does not, and why it carries a different interaction profile.
The approval was granted on statistically significant but clinically modest improvements, and this has been the subject of substantive critique. Worth knowing before expecting a dramatic effect.
Unproven — inference onlyExtrapolated from a known mechanism, receptor profile, or adjacent compound class. Biologically plausible but not directly demonstrated for this compound in this context.
Off-label everywhere, supported by the earlier male ED programme, and the dominant community use. Not the approved population and not the studied dose regimen.
Explicitly outside the approved indication, which is limited to premenopausal women.
The most mechanistically defensible extension, supported by the male trial data.
More MC4R-weighted, so less tanning. Not absent, and as-needed dosing limits cumulative exposure anyway.
Uncontrolled reportsAggregated from research-community logs, forums, vendor literature and self-reported experience. Uncontrolled, unverified, subject to placebo, polypharmacy and product-purity confounds. Lowest evidentiary weight.
The characteristic report, described as psychological rather than physical — which matches the central mechanism precisely.
Frequently reported to persist well beyond the dosing window, which is part of why the labelled frequency limit exists.
The main complaint, dose-related and consistent with trial data.
Common and transient.
Doses of 1–2 mg are common against a labelled 1.75 mg maximum with a strict frequency cap that is widely ignored.
Adverse effects, contraindications and unknowns. The grey-market tier is where under-reporting is worst: uncontrolled use produces no systematic safety surveillance at all, so absence of a reported harm is not evidence of safety.
Highest confidenceReported in peer-reviewed literature, registered clinical trials, or regulatory filings. Note the model: much peptide literature is in vitro or rodent work, not human trial data.
Reported by a large proportion of trial participants, dose-related, and the leading cause of discontinuation.
Labelled. Contraindicated in uncontrolled hypertension and known cardiovascular disease, and the reason the intranasal formulation was abandoned.
Labelled, occurring more frequently with repeated dosing and sometimes not resolving after discontinuation. Melanocortin agonism does not stop being pigmentary because the indication changed.
Common labelled adverse effects.
No more than one dose in 24 hours and no more than eight doses per month — a frequency restriction rather than only a dose restriction, which is unusual and reflects the pigmentation and blood-pressure findings.
Unproven — inference onlyExtrapolated from a known mechanism, receptor profile, or adjacent compound class. Biologically plausible but not directly demonstrated for this compound in this context.
The labelled monthly cap exists for this reason. Community use ignoring it increases exactly the exposure the cap limits.
A transient pressor effect matters most in exactly the population least likely to have been screened.
A melanocortin class concern, reported with melanotan-2 and a urological emergency.
Uncontrolled reportsAggregated from research-community logs, forums, vendor literature and self-reported experience. Uncontrolled, unverified, subject to placebo, polypharmacy and product-purity confounds. Lowest evidentiary weight.
The dominant complaint, and the usual reason people reduce the dose.
Common and transient.
Reported, and exactly what the label warns about.
Reported as a pressure or head-fullness feeling shortly after dosing.
Figures below are documented, not recommended. Study ranges come from published protocols in the stated model; grey-market ranges are what the research community reports using and carry no safety validation of any kind.
Highest confidenceReported in peer-reviewed literature, registered clinical trials, or regulatory filings. Note the model: much peptide literature is in vitro or rodent work, not human trial data.
Administered at least 45 minutes before anticipated sexual activity, with a maximum of one dose per 24 hours and eight doses per month.
Earlier male studies used subcutaneous and intranasal routes across a dose range; the intranasal programme was discontinued over blood pressure.
| Setting | Dose | Route | Frequency limit |
|---|---|---|---|
| Vyleesi (approved, HSDD) | 1.75 mg | Subcutaneous | Max 1/24h, 8/month |
| Male ED trials | Trial-defined | SC and intranasal | Study protocol |
Unproven — inference onlyExtrapolated from a known mechanism, receptor profile, or adjacent compound class. Biologically plausible but not directly demonstrated for this compound in this context.
Nausea is the dose-limiting effect and it is dose-related. Starting lower and titrating is the coherent approach.
The cap addresses cumulative pigmentation, which is the effect community use most reliably produces by exceeding it.
Unlike almost everything else in this library, PT-141 is designed for as-needed use. Daily dosing has no basis at all.
Uncontrolled reportsAggregated from research-community logs, forums, vendor literature and self-reported experience. Uncontrolled, unverified, subject to placebo, polypharmacy and product-purity confounds. Lowest evidentiary weight.
A common community dose below the label, used to manage nausea.
The approved figure.
Above the label, with correspondingly worse nausea and no evidence of greater efficacy.
| Approach | Dose | Timing | Notes |
|---|---|---|---|
| Conservative | 0.5 – 1 mg | 45–120 min before | Nausea management |
| Label-matched | 1.75 mg | ≥45 min before | Approved figure |
| Above label | 2 mg+ | Variable | More nausea, no added benefit shown |
Combination effects. Almost no peptide combination has been studied as a combination in humans; stack logic is overwhelmingly mechanistic inference and community practice. Each linked compound has its own page.
Highest confidenceReported in peer-reviewed literature, registered clinical trials, or regulatory filings. Note the model: much peptide literature is in vitro or rodent work, not human trial data.
None exists.
Unproven — inference onlyExtrapolated from a known mechanism, receptor profile, or adjacent compound class. Biologically plausible but not directly demonstrated for this compound in this context.
Intranasal oxytocin is sold heavily on desire, trust and intimacy claims. It has no approval for any of them anywhere, and the most rigorous trial in that literature was negative. PT-141 is the compound in this space with a randomised evidence base and an approval, acting through melanocortin receptors rather than the oxytocin system. The two are frequently discussed together and are not comparable on evidence.
Central desire plus vascular response is the mechanistically complementary pairing. Both affect blood pressure, and the combination has not been characterised for that.
PT-141 is an MT-2 metabolite acting on the same receptor family. Running both is melanocortin agonism twice over.
Both influence sexual function by different routes — kisspeptin upstream at the HPG axis, PT-141 centrally on desire. Untested together.
A compound with a labelled pressor effect in someone being treated for blood pressure deserves attention.
Uncontrolled reportsAggregated from research-community logs, forums, vendor literature and self-reported experience. Uncontrolled, unverified, subject to placebo, polypharmacy and product-purity confounds. Lowest evidentiary weight.
Commonly reported for male use.
Whole schedules — dosing, titration, cycle length, and off-time — as documented in trials, as proposed from mechanism, and as circulated in the research community. Reproduced for study and comparison only.
Highest confidenceReported in peer-reviewed literature, registered clinical trials, or regulatory filings. Note the model: much peptide literature is in vitro or rodent work, not human trial data.
Randomised placebo-controlled as-needed dosing in premenopausal women with HSDD, with validated desire and distress instruments as endpoints.
Unproven — inference onlyExtrapolated from a known mechanism, receptor profile, or adjacent compound class. Biologically plausible but not directly demonstrated for this compound in this context.
The regimen the approval was granted on, and the one that limits the cumulative pigmentation effect.
Given a labelled pressor effect and a cardiovascular contraindication, this is trivially easy and directly relevant.
Uncontrolled reportsAggregated from research-community logs, forums, vendor literature and self-reported experience. Uncontrolled, unverified, subject to placebo, polypharmacy and product-purity confounds. Lowest evidentiary weight.
The general community pattern, frequently exceeding the monthly cap.
Neither the Gold Standard Protocol nor the 15-Compound Matrix includes it.
PT-141 is one of very few compounds in this library that is approved for the thing people actually want it for. That makes this section unusual: the job is not to explain why the evidence is thinner than claimed, but to explain how narrow the approval is and how far ordinary use sits outside it.
Approved as Vyleesi (bremelanotide) for acquired, generalised hypoactive sexual desire disorder in premenopausal women. The label is specific: premenopausal, on-demand, no more than one dose in 24 hours and no more than eight in a month, and contraindicated in uncontrolled hypertension or known cardiovascular disease. Almost every off-label use ignores at least one of those bounds, and the dose limits exist for a documented reason.
Pathophysiology
HSDD is persistent, distressing absence of sexual desire. In the acquired generalised form the person previously had desire and lost it, in all contexts. Distress is part of the diagnosis — low desire without distress is not a disorder.
Mechanistic rationale
Bremelanotide acts centrally at melanocortin receptors in pathways governing sexual desire, which is a genuinely different mechanism from the vascular one PDE5 inhibitors use. Randomised trials supported approval on improvements in desire and in the distress associated with it. The effect size is real and modest, which is what the trial reports say and what the label reflects.
Community reports
The approved population reports it working sometimes rather than always, which matches an on-demand agent with a modest effect. Expectation management is a large part of clinical use.
Components carrying the argument: Melanocortin receptor agonism, central
Pathophysiology
Erectile dysfunction has vascular, neurological, hormonal and psychological contributors. PDE5 inhibitors act on the vascular final common pathway and fail in people whose problem is upstream of it.
Mechanistic rationale
The central mechanism is the interesting part: it acts on desire and arousal rather than on penile blood flow, which is why it has been investigated in men who do not respond to PDE5 inhibitors. Development in male sexual dysfunction did not produce an approval, and the reasons — blood pressure effects on the original intranasal route, and nausea — are on this page rather than hidden.
Community reports
The dominant off-label use, frequently in men who already tried PDE5 inhibitors. Often combined with them, which stacks two mechanisms and two side-effect profiles with no interaction data.
Components carrying the argument: Central arousal pathways, not vascular
Pathophysiology
Melanocortin receptor agonism produces a transient rise in blood pressure and a fall in heart rate, peaking within hours of dosing and resolving over roughly half a day.
Mechanistic rationale
This is why it is contraindicated in uncontrolled hypertension and in known cardiovascular disease, and why the label caps dosing at one per day and eight per month. The original intranasal development programme was abandoned in part because of blood pressure increases. Community dosing frequently exceeds the monthly cap, in a population — middle-aged men with erectile dysfunction — with an elevated prevalence of exactly the cardiovascular disease that constitutes the contraindication.
Community reports
Flushing and headache are commonly reported and are consistent with the haemodynamic effect. Blood pressure is rarely measured by people using it.
Components carrying the argument: Melanocortin-mediated haemodynamic effect
Pathophysiology
The penile arteries are small. Endothelial dysfunction and atherosclerosis frequently manifest there before they manifest in the coronary circulation, which is larger and tolerates more narrowing before symptoms appear.
Mechanistic rationale
New erectile dysfunction is an independent predictor of cardiovascular events, often years in advance, and a proper workup is a cardiovascular risk assessment as much as a sexual one. Treating the symptom with a compound bought online skips the part where a warning sign gets investigated. That is the single most consequential point on this page and it has nothing to do with the pharmacology.
Community reports
Almost never raised in community discussion, where ED is framed as a performance problem rather than a vascular one.
Components carrying the argument: Not a mechanism — a diagnostic opportunity being skipped
Pathophysiology
Melanocortin receptors are expressed in brainstem regions involved in nausea and emesis.
Mechanistic rationale
Nausea affects a large proportion of users in trials — it is the most common adverse event by a wide margin and the most common reason for discontinuation. It is dose-related, which is one reason the approved dose is where it is. Community dosing above the labelled amount predictably makes it worse rather than making the effect stronger.
Community reports
Consistently the top complaint. Users commonly describe taking an antiemetic alongside, which is treating a dose problem with another drug.
Components carrying the argument: Central melanocortin effects
Pathophysiology
MC1R activation on melanocytes drives melanin production. Bremelanotide is less selective for the receptors governing sexual function than its marketing implies.
Mechanistic rationale
Focal hyperpigmentation — on the face, gums and breasts — is a labelled adverse effect, more likely with frequent dosing, and it does not always fully resolve. This is the same receptor family that makes Melanotan-2 the compound it is, which is why exceeding the monthly cap moves this compound toward that one’s problems.
Community reports
Reported by heavier users, and is one of the clearest signals that dosing has gone beyond the studied range.
Components carrying the argument: MC1R cross-activation
Pathophysiology
Not a condition. A scope note.
Mechanistic rationale
The approval is for premenopausal women with acquired generalised HSDD. It does not cover postmenopausal women, men, situational low desire, low desire without distress, or use as a recreational enhancer in people with normal function. Each of those is a use with no efficacy data and the full adverse effect profile, and the last is the most common one.
Community reports
Recreational use in people without dysfunction is widespread and is the furthest of any use from the evidence.
Components carrying the argument: —
| Question | Position |
|---|---|
| Approved? | Yes — Vyleesi, premenopausal women, acquired generalised HSDD |
| Dose limits | 1 per 24 h, 8 per month |
| Contraindicated in | Uncontrolled hypertension, known cardiovascular disease |
| Mechanism | Central melanocortin — desire, not blood flow |
| Most common adverse effect | Nausea — dose-related, dose-limiting |
| Hyperpigmentation | Labelled; more likely with frequent dosing |
| New erectile dysfunction | Investigate it — it predicts cardiovascular events |
| Approved for men? | No |
For erectile dysfunction: PDE5 inhibitors are effective, inexpensive and well understood, and a proper ED workup treats the symptom as the cardiovascular warning sign it frequently is — blood pressure, lipids, glucose, smoking status and testosterone where indicated. Vacuum devices, intracavernosal therapy and implants exist for non-responders.
For low sexual desire: the highest-yield questions are relationship factors, psychological ones, and medication review — SSRIs in particular are a very common and very reversible cause. Treating depression, treating sleep disorder, reducing alcohol, and assessing testosterone where clinically indicated come before any pharmacological approach to desire itself. Sex therapy has an evidence base and is under-used.
For HSDD specifically: bremelanotide and flibanserin are both approved, both have modest effect sizes, and both work best alongside psychological treatment rather than instead of it.
Physical-chemistry reference for laboratory handling of the lyophilised material. Reproduced so that stability and concentration mathematics can be studied — see the calculator for the arithmetic and the reconstitution guide for sterile technique.
The approved product ships as a single-use autoinjector. Research supply is lyophilised, commonly 10 mg per vial. At 1 mg per use a 10 mg vial covers ten uses, which given as-needed dosing means a long in-use period.
Lyophilised: refrigerated or frozen. Reconstituted: 2–8 °C.
Approved: 1.75 mg autoinjector. Research supply: commonly 10 mg vials.
As-needed use means a reconstituted vial may sit for months — the same in-use problem that affects the weekly metabolic compounds.
Regulatory status changes and differs by country. This is a summary for orientation, not legal advice — check your own jurisdiction.
Approved as Vyleesi (bremelanotide) by the FDA for acquired, generalised hypoactive sexual desire disorder in premenopausal women. It is a prescription medicine with a defined label, contraindications and dose-frequency limits.
All other use — men, postmenopausal women, general libido enhancement — is off-label. Material sold as research-grade PT-141 is not the approved product.
Regulatory and trial claims re-checked against primary sources on 16 August 2026. Checked: Vyleesi still marketed in the US; no EU, UK or Canadian authorisation. Approvals, trial readouts and compounding decisions move faster than anything else on this page — a date here means someone looked, not that nothing has changed since.
Athletes subject to WADA, USADA, UKAD, NCAA or military testing should assume any peptide is prohibited unless they have verified otherwise against the current WADA Prohibited List. Several classes here (growth-hormone secretagogues, TB-4 analogues, metabolic modulators) are explicitly named. Check the current list — it is republished annually.
Links resolve to PubMed records, trial registries, publisher pages or primary documents. Where a body of work rather than a single paper is cited, the link opens a PubMed query so the full result set — including newer papers than this page — can be reviewed. Verify every claim against the primary source before relying on it.
For educational and research reference only. Nothing on this site is medical advice, a recommendation, or an instruction to administer any substance to a human being. Every figure on this page is a record of what has been reported, not a recommendation. Full disclaimer.
