PT-141 Bremelanotide 10mg - Atlas Lab

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What the parcel contains

One sealed vial of PT-141 10mg, lyophilised, without individual labelling.

What you also need

Bacteriostatic water for reconstitution and 1 ml precision syringes graduated in 100 units, sold separately. The vial alone cannot be used as is.

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PT-141, or bremelanotide, is a synthetic cyclic heptapeptide Ac-Nle-cyclic[Asp-His-D-Phe-Arg-Trp-Lys]-OH of molecular weight 1025 Da, derived from alpha-MSH (melanotropic hormone) through successive structural modifications of Melanotan II. It is the result of a research programme initiated in the 1990s at the University of Arizona, then industrialised by Palatin Technologies. In 2019, the US FDA approved bremelanotide under the commercial name Vyleesi for the treatment of hypoactive sexual desire disorder (HSDD) in premenopausal women, following two randomised phase 3 trials (RECONNECT) totalling more than 1247 patients.

Its pharmacological originality is profound: unlike PDE5 inhibitors (sildenafil, tadalafil) which act peripherally on penile or clitoral vessels, PT-141 acts centrally on the central nervous system, at the melanocortin MC3R and especially MC4R receptors located in the hypothalamus. It thus activates desire itself, upstream of the vascular cascade, and also works in non-responders to PDE5 (diabetic neuropathy, post-prostatectomy nerve injury, psychogenic dysfunction).

This vial delivers 10 mg of high-purity PT-141 (>98 %, HPLC) in lyophilised form, type I borosilicate glass, fluorinated butyl stopper, argon atmosphere. The standard documented dose (1.75 mg SC as a single dose) allows approximately 5-6 uses per vial. Destined exclusively for in vitro research and preclinical studies on non-human models, in accordance with European regulations; no human, dietary or medical use.

Science

01
Mechanism of action

The PT-141 mechanism is central and articulates primarily around melanocortin receptors. Five subtypes MC1R-MC5R exist in humans: MC1R (skin/hair pigmentation), MC2R (adrenal cortex, cortisol), MC3R and MC4R (central nervous system, food intake, sexual function), MC5R (exocrine glands). PT-141 is a preferential MC3R/MC4R agonist with reduced affinity for MC1R (key difference with Melanotan II, which minimises pigmentation).

MC4R activation in the paraventricular nucleus of the hypothalamus triggers a neuroendocrine cascade: oxytocin release from magnocellular neurons, dopamine increase in the ventral tegmental area and nucleus accumbens (reward circuits), spinal parasympathetic activation (sacral parasympathetic nucleus). These three effects converge towards facilitation of sexual arousal: oxytocin modulates motivation and attachment, dopamine creates anticipatory desire, and parasympathetic activation potentiates the peripheral vascular response (tumescence).

Unlike PDE5 inhibitors, PT-141 does not act directly on guanylate cyclase or vascular nitric oxide. It cannot therefore cause prolonged erection of the priapism type by blocking the detumescence inhibitor system. The erection or lubrication obtained under PT-141 remains controlled by normal physiological mechanisms, simply potentiated by activated central desire.

Pharmacokinetics: after subcutaneous injection of 1.75 mg, plasma peak in 1 hour, half-life 2-2.7 hours, urinary elimination. Biological effect (desire and arousal) peaks at 1-2 hours, perceptible duration 4-10 hours depending on subjects. Metabolisation is minimal, the peptide is excreted intact or slightly hydrolysed.

Central collateral effect: MC4R hypothalamic stimulation also affects appetite (transient reduction 20-40 %), anxiety (variability between subjects: mild anxiolysis for some, activation for others) and thermoregulation. Residual MC1R activation can cause discreet tanning at repeated doses.

The most frequent side effect is nausea (~40 % of subjects in RECONNECT trials), mediated by MC4R activation central and peripheral at the chemoreceptor vomiting zone. This nausea is moderate, dose-dependent and attenuated by injection after light meal, preventive antiemetic, or dose fractionation.

Clinical data

02Clinical studies

PT-141 and bremelanotide literature covers more than 100 publications over 20 years.

Discovery and initial development: Wessells 1998 Urology described the first human trial on 10 men with erectile dysfunction, showing a dose-dependent erectile response by intranasal and subcutaneous routes. Rosen 2004 J Sex Med confirmed on 271 ED men the effect on 30 % of better satisfactory erections versus placebo, including in sildenafil non-responders. Diamond 2006 J Sex Med published the first female data on 18 subjects with female sexual arousal disorder.

Female HSDD clinical development: Clayton 2016 Obstet Gynecol and Kingsberg 2019 Obstet Gynecol (pivotal RECONNECT-I and II trials) included 1247 premenopausal women with HSDD over 24 weeks, with bremelanotide 1.75 mg SC PRN (as needed, before sexual activity). Results: significant increase in FSFI-desire score (+0.5 to +0.7 vs placebo), reduction in FSDS sexual distress score, 35-45 % clinically significant responders. This trial supported 2019 FDA approval.

Male erectile dysfunction non-responder to PDE5: Safarinejad 2008 Int J Impot Res showed in 120 sildenafil/tadalafil non-responder men a response rate of 33 % under PT-141 SC 20 mg versus 8 % placebo. Molinoff 2003 Int J Impot Res studied the intranasal route (former formulation) in 271 ED men. Male indication was not pushed to approval by Palatin after intranasal development was stopped.

Neurobiology and animal models: Pfaus 2011 Obstet Gynecol Clin North Am summarised PT-141 neurobiology in rat and primate models: activation of hypothalamic oxytocin, lordosis in female rats in receptive behaviour, restoration of sexual behaviour after castration. Andersson 2011 Eur Urol characterised nerve pathways by c-Fos brain imaging.

Cardiovascular: the RECONNECT trial measured a transient elevation of systolic blood pressure of 1.9 mmHg and diastolic of 1.7 mmHg after injection (peak 2-4h), without clinical impact in healthy subjects. In poorly controlled hypertensive subjects, monitoring is recommended. No pressor rebound after 10 hours.

Pharmacovigilance: on Vyleesi sales since 2019, the profile is consistent with trials: nausea 40 %, hot flashes 20 %, headache 15 %, site pain 13 %. No priapism reported (different mechanism from PDE5). A few rare cases of focal cutaneous pigmentation reported in chronic use (residual MC1R activation).

Off-label and community male use: PT-141 is used off-label in men for ED non-responder to PDE5 and in longevity/performance research communities. Observational data are abundant but non-randomised.

Critical limitation: the RECONNECT trial was criticised for the modesty of the clinical effect (increase of 0.5-0.7 point FSFI on a 1-5 scale), the high dropout proportion (23 %), and the large placebo effect (20-25 % placebo responders). PT-141 remains a useful tool but not a magic solution. In men, the absence of a dedicated phase 3 trial limits generalisations.

1
Trouble du désirBremelanotide for the Treatment of Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials
Kingsberg SA, Clayton AH, Portman D, et al. · Obstetrics & Gynecology · 2019
2
Excitation sexuelleAn effect on the subjective sexual response in premenopausal women with sexual arousal disorder by bremelanotide (PT-141)
Diamond LE, Earle DC, Heiman JR, Rosen RC, Perelman MA, Harning R · Journal of Sexual Medicine · 2006

The listed studies are provided for documentation and research purposes only. They do not constitute a therapeutic indication nor a recommendation for human use. This product is strictly for laboratory use only (RUO).

Lab workflow

03
Research protocols

Standard reconstitution: slowly inject 2 ml of bacteriostatic water into the 10 mg vial, creating a 5 mg/ml solution that is clear to slightly pale yellow. Gently roll, do not shake.

Typical working concentrations:
- Standard female dose (Vyleesi reference): 1.75 mg = 0.35 ml
- Standard male dose (off-label literature): 1.5-2 mg = 0.3-0.4 ml
- Reduced dose (first trial, assess nausea tolerance): 0.75-1 mg = 0.15-0.2 ml
- Maximum RECONNECT trial dose: 1.75 mg (no documented benefit beyond)

Typical frequency in research protocols:
- PRN (as needed) use: one injection 45 minutes to 2 hours before planned activity
- Minimum spacing: 24 hours between 2 injections
- Maximum documented frequency: 8 doses per month (Vyleesi label)
- Continuous daily use: not documented, not recommended (tachyphylaxis and cumulative pigmentation risk)

Administration route: subcutaneous in the abdomen or thigh (Vyleesi standard). The intranasal route was abandoned in industrial development (erratic bioavailability). Some historical studies used IV but SC is the norm.

Specific points of vigilance for PT-141:
1. Nausea: the most frequent side effect (~40 %). Anticipate: inject after a light meal (not too heavy either so as not to slow absorption), ginger 30 min before, or preventive 4 mg ondansetron in sensitive subjects.
2. Hot flashes and facial flush: frequent in the 30-60 min after injection, transient.
3. Transient blood pressure elevation: monitor in hypertensive subjects, do not use in case of severe uncontrolled hypertension or recent cardiovascular event.
4. Cutaneous pigmentation: residual MC1R activation. At occasional doses (<8/month), not observed. In chronic daily use, possible appearance of focal spots.
5. Alcohol interaction: alcohol increases nausea and drowsiness; limit consumption.
6. Delayed effect: effect peak at 1-2 hours. Inject 45 min to 2 hours before planned sexual activity, not just before.

Documented synergies:
- With PDE5 (sildenafil, tadalafil): complementary mechanisms, PT-141 acts on desire, PDE5 on vasodilation. Combinations are empirically described but few formal studies. Monitor blood pressure.
- With oxytocin (intranasal): both activate oxytocin but through different pathways, theoretical addition.

This product is not intended for human use. The protocols described are examples drawn from scientific literature and documented off-label practices, provided strictly for informational purposes for research work on non-human models.

Reconstitution for this format (10 mg)Standard volumes used in laboratory settings

Water added	Concentration	Reading marker
1 ml	10 mg/ml	10 UI = 1 mg
2 ml	5 mg/ml	40 UI = 2 mg

The volume of water does not change the product, only its concentration. Introduce the water slowly along the vial wall, never directly onto the lyophilisate, then swirl without shaking. Markers given on a 1 ml syringe graduated in 100 units.

Asepsis

Disinfect surfaces and stoppers (70% alcohol).

Solvent

Draw the required volume of bacteriostatic water.

Introduction

Inject gently against the vial wall (avoid direct jet on powder).

Solubilization

Roll the vial gently. Do not shake vigorously (degradation risk).

Solution storageOnce reconstituted: 2-8°C (refrigerator).

WarningTheoretical tool for chemical handling. Does not constitute medical advice.

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What is normal on arrivalThe observations that worry customers, and are not defects

The amount of powder looks tiny. A lyophilisate takes up a few millimetres at the bottom of the vial, sometimes just a translucent film. The stated weight is there.
The powder is compact, stuck to the wall or to the stopper. Transport moves the freeze-dried cake around. It changes nothing to reconstitution.
The vial carries no individual label. That is our standard packaging, not a downgraded vial.
After reconstitution, deposits or filaments appear. This is common, especially with small molecules. Let it settle and roll the vial between your palms, never shake it.
The parcel is plain. Nothing on the outside indicates the contents or the brand name.

What is not normal: a cracked vial, an uncrimped cap or a stopper that moves, powder that has liquefied or changed colour. In those specific cases, write to us with a photo and we take the vial back.

Handling

04Storage & handling

Sealed unreconstituted vial: -20 C in laboratory freezer, stability 24 months. At 2-8 C, stability 12 months. At room temperature (20-25 C), maximum 30 days stability; beyond, hydrolysis of peptide bonds and oxidation of N-terminal methionine (Nle in PT-141 is the methionine replacement precisely to reduce this risk).

After reconstitution in bacteriostatic water:
- 4-8 C (refrigerator): optimal stability 14 days, acceptable up to 21 days with strict hygienic handling.
- -20 C: acceptable for aliquots. One freeze-thaw cycle tolerated; avoid multiple cycles.
- Light: keep protected.
- pH: solution stable pH 4.5-6.5.

Visual signs of degradation:
1. Cloudy veil or precipitate: peptide aggregation, structural degradation.
2. Deep yellow coloration: Trp or His oxidation, reduced activity.
3. Abnormal odour: advanced degradation.

Aliquoting: for spaced use (1-2 injections per month), keeping the reconstituted vial refrigerated is sufficient. For very spaced use (less than one injection per month), prefer aliquoting in 5 microtubes of 0.4 ml frozen, used as needed.

Laboratory documentation: reconstitution date, COA lot, storage conditions, to be recorded for traceability.

01How does PT-141 differ from PDE5 inhibitors like Viagra?

Viagra (sildenafil) acts peripherally on genital blood vessels by inhibiting PDE5. PT-141 acts centrally in the hypothalamus via MC4R receptors, activating desire and arousal at the source. Result: PT-141 works even in PDE5 non-responders and targets desire, not just erection. Both can be complementary.

02How long before observing the effect?

Effect peak at 1-2 hours after subcutaneous injection. It is recommended to inject 45 minutes to 2 hours before planned activity. The perceptible duration of the effect is 4-10 hours depending on subjects, with gradual return to baseline.

03Is nausea unavoidable?

Approximately 40 % of subjects in clinical trials report nausea, generally moderate and transient (1-2 hours). Attenuation strategies: injection after a light meal, preventive ginger, antiemetic like ondansetron 4 mg 30 min before in very sensitive subjects, or dose fractionation (1 mg then 0.75 mg at 30 min).

04Can it be used daily?

Not recommended. Vyleesi label limits to 8 doses per month maximum. Daily use would risk tachyphylaxis (effect loss through MC4R receptor desensitisation) and cumulative cutaneous pigmentation (residual MC1R activation). Ideal spacing: 24-72h between two injections depending on desired frequency.

05Is there a risk of priapism?

Not documented. The central mechanism of PT-141 does not block physiological detumescence. Unlike PDE5, no cases of priapism have been reported in RECONNECT phase 3 nor in Vyleesi pharmacovigilance since 2019.

06Does PT-141 work in men?

Phase 2 studies (Rosen 2004, Safarinejad 2008) showed a response rate of 30-33 % in men with ED, including sildenafil non-responders. The male indication did not result in FDA approval (intranasal development abandoned by Palatin). Off-label male use is described but without dedicated phase 3 trial.

07Can PT-141 be combined with sildenafil or tadalafil?

Mechanisms are complementary (central vs peripheral). Combinations are empirically described in off-label communities but not in formal clinical trials. Points of vigilance: monitor blood pressure (PT-141 can transiently increase, PDE5 can decrease), space doses, start with half the usual dose of each.

08Is cutaneous pigmentation a problem?

At usual doses (occasional 1.75 mg, <8 times/month), pigmentation is not documented in clinical trials. In chronic daily off-protocol use, rare cases of focal spots have been reported through residual MC1R activation. PT-141 was designed to minimise this effect, but selectivity is not absolute.

Benchmark

Similar peptides

PT-141 differs radically from other sexual sphere agents through its central mechanism and activity spectrum.

Versus PDE5 inhibitors (sildenafil, tadalafil, vardenafil): PDE5 inhibitors act peripherally on genital vasodilation by preventing cGMP degradation. PT-141 acts centrally on desire. Mechanisms are complementary, non-competitive. PDE5 are ineffective if central activation is lacking (absent desire, ineffective stimulation), PT-141 is effective even in PDE5 non-responders. In combination, effects may be additive but increase the risk of flush and hypotension (both modulate blood pressure differently).

Versus testosterone (male or female replacement therapy): testosterone corrects an underlying hormonal deficit with effects over several weeks-months. PT-141 acts acutely over a few hours. In hypogonadic patients, testosterone must be corrected before evaluating PT-141. In women with testosterone-normal HSDD, PT-141 is a non-hormonal option.

Versus flibanserin (Addyi, serotonergic for female HSDD, FDA approved 2015): flibanserin is a 5HT1A agonist/5HT2A antagonist in daily intake (nightly to limit drowsiness), with modest effect and major alcohol interaction (alcohol prohibition required). PT-141 is PRN (as needed), without such severe alcohol restriction, with faster effect. Different side effect profiles (flibanserin: drowsiness, hypotension; PT-141: nausea, flush).

Versus Melanotan II (pharmacological precursor): MT-II is the ancestor of PT-141, non-selective MC1R/MC3R/MC4R/MC5R agonist. It causes marked pigmentation (MC1R) and sexual effect recognised as side effect in early users. PT-141 was designed to minimise MC1R and maximise MC4R: improved selectivity, pigmentation almost absent at usual doses.

Versus apomorphine (dopamine D2 agonist, former ED treatment): central dopaminergic mechanism. Moderate tolerance, frequent nausea. Withdrawn from the US market in 2003. PT-141 has a non-dopaminergic melanocortin profile, complementary.

Versus cognitive-behavioural and couple therapies: PT-141 does not replace the psycho-relational approach. In RECONNECT, the placebo effect was 20-25 %, underlining the important psychogenic component of HSDD. An integrated approach (peptide + therapy + hormones if deficit) is often superior to each isolated component.

Versus other research catalogue peptides (Kisspeptin-10 gonadotropic, intranasal Oxytocin, DSIP for sleep): different neuroendocrine targets. Kisspeptin modulates the GnRH axis (endogenous LH/FSH production), oxytocin acts directly on attachment/trust system, DSIP on sleep. PT-141 is the only catalogue peptide oriented directly towards central sexual desire.

Unique positioning: the only research catalogue peptide with FDA approval in a female sexual indication, innovative central mechanism, substantial clinical corpus in women, documented off-label use in male PDE5 non-responder. It is a specific tool not to be trivialised but whose place in the research peptide arsenal is clear.

PT-141 10mg Wellbeing

Neuromodulation

01
Mechanism of action

02Clinical studies

03
Research protocols

Asepsis

Solvent

Introduction

Solubilization

04Storage & handling

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Neuromodulation

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