PT-141 at a glance
PT-141 is the laboratory code for bremelanotide, a cyclic heptapeptide from the melanocortin agonist class. Its ring is identical to that of Melanotan-2. The two differ only at the C-terminus: bremelanotide finishes in a free acid where Melanotan-2 carries an amide, which makes it about 1 Da heavier, 1025.2 against 1024.2. Palatin Technologies, a US company, developed it after early Melanotan-2 studies showed that a melanocortin agonist can bring on erections through the brain.
Bremelanotide went through a complete clinical programme, and in 2019 the US Food and Drug Administration approved it under the brand name Vyleesi. The molecule is therefore a licensed medicine in one jurisdiction. A vial of research powder with the same sequence is not.
- Cyclic heptapeptide, 1025.2 Da, non-selective melanocortin agonist.
- Licensed in the US as Vyleesi for hypoactive sexual desire disorder (HSDD) before the menopause; no EU authorisation.
- Not listed by King Peptides; the closest product there is a different compound.
How PT-141 works
Bremelanotide switches on melanocortin receptors. The US label calls it a non-selective agonist and ranks its potency as MC1R, MC4R, MC3R, MC5R, MC2R, adding that MC1R and MC4R are the two that count at therapeutic doses. MC4R neurons in brain areas tied to sexual motivation are thought to carry the effect on desire. Activity at MC1R, the pigment receptor, explains a side effect: skin and gums can darken.
Sildenafil and related PDE5 inhibitors act on blood vessels and do nothing without sexual stimulation, whereas bremelanotide is dosed ahead of time and acts on signalling in the brain. Its side effects are accordingly systemic, not local.
After a 1.75 mg subcutaneous dose, the label reports peak concentration at roughly one hour and a half-life of about 2.7 hours. An earlier nasal spray was abandoned in 2008 when blood pressure rose in users, and development moved to subcutaneous injection, which gave steadier blood levels.
The evidence ladder for PT-141
| Evidence level | Model or trial | Main finding |
|---|---|---|
| Human pharmacology | Vyleesi label; 1.75 mg subcutaneous | Peak concentration after about 1 hour; half-life about 2.7 hours |
| Randomised trials | Two phase 3 trials of identical design, double-blind with placebo control; 1,247 premenopausal women in total; 24-week core phase plus a 52-week open-label extension | Superior to placebo in both trials on the two co-primary end points: desire, scored on the Female Sexual Function Index, and distress about low desire. For the secondary end point, the number of satisfying sexual events, no significant difference emerged |
| Licensed use | Vyleesi, approved by the US FDA in 2019 | Acquired, generalised HSDD in premenopausal women; not approved for postmenopausal women or for men |
This ladder reaches the top rung. The end points that reached significance were questionnaire scales, however, and the differences from placebo were modest. The approved indication is also narrow: it excludes low desire that stems from illness, medical or psychiatric, from relationship difficulties or from medication.
Bremelanotide had earlier been studied in men with erectile dysfunction, but the approval does not cover men. The ladder also ends at the US border, as it does for tesamorelin, another peptide approved in the United States and not authorised in the EU.
PT-141 doses reported in studies
The figures below describe a licensed US product and its trials. They are reference values, not guidance, and they do not apply to research material.
| Setting | Dose | Schedule | Route | Note |
|---|---|---|---|---|
| US licensed product (Vyleesi label) | 1.75 mg | Given 45 minutes or more ahead of expected sexual activity; label ceiling of one dose per 24 hours and eight doses per month | Subcutaneous, autoinjector | To be discontinued if nothing has improved after 8 weeks |
| Phase 3 trials | 1.75 mg, compared with placebo | On demand, 24-week core phase | Subcutaneous | 1,247 women in total |
The EU has authorised no dose at all.
Safety findings and open questions
The US label gives these rates for drug versus placebo: nausea 40.0% versus 1.3%, flushing 20.3% versus 0.3%, headache 11.3% versus 1.9%. About 8% of women gave up treatment because of nausea. Vomiting and reactions at the injection site also exceeded placebo.
Each dose raises blood pressure for a while, systolic by as much as 6 mmHg and diastolic by 3 mmHg, and slows the heart by up to 5 beats per minute; both return to baseline within 12 hours. Uncontrolled hypertension and known cardiovascular disease are contraindications on the label. Focal hyperpigmentation, seen on the face, the gums or the breasts, affected 1% of trial patients, who used at most eight doses a month, but 38% of participants in a separate study with daily dosing for eight days. It did not fade in everyone after stopping. Bremelanotide can also markedly lower exposure to oral naltrexone, so the label warns against combining the two.
- By what mechanism does the drug improve low desire? The label itself says this is unknown.
- How do benefit and risk look in postmenopausal women or in men? No approval covers them.
- Do label data carry over to research powder? No: they describe a product made and released under pharmaceutical rules.
Bench notes: storing and reconstituting PT-141
Research-grade bremelanotide is a lyophilised powder, and the reference data give −20 °C as its storage temperature. Keep vials sealed, dry and dark, and let them warm to room temperature before opening.
Laboratories normally reconstitute with bacteriostatic water: add the solvent slowly along the glass wall, swirl and do not shake. Keep the solution refrigerated and use aliquots to avoid cycles of freezing and thawing. The storage and reconstitution protocol has the details.
Status in the Netherlands, Belgium and Luxembourg
Bremelanotide is a US medicine without an EU marketing authorisation. Authorisations issued through the European Medicines Agency apply in the Netherlands, Belgium and Luxembourg alike, and the agency has not authorised this drug. What is sold here under the name PT-141 is a research chemical: it is not the US product, and it is not for human use.
Under EU law, a substance presented as a treatment, or used to modify a physiological function pharmacologically, is a medicinal product and needs authorisation before it reaches the market. Possession and personal import are regulated nationally, and institutions add rules of their own, so check what applies to you. The primer on research peptides explains how far a licensed medicine and a research compound are apart.
For sport, the WADA S0 category is reserved for substances that lack approval for human therapeutic use everywhere. A compound approved in the United States falls outside that wording. Athletes should still consult the current Prohibited List.
Ordering PT-141 for research in the Benelux
King Peptides does not list PT-141. The nearest item in the shop is Melanotan II 10 mg, and that is a different compound, not bremelanotide under another label. Melanotan II shares the ring, but its C-terminus is an amide, its receptor profile (MC1R, MC3R, MC4R and MC5R, without selectivity) is its own, and its clinical development was never completed. A result obtained with one cannot be credited to the other.
Identity is settled on the certificate of analysis. Look for the lot number of the vial, an HPLC purity of 99% or higher, which is what the shop lists for Melanotan II 10 mg, and a mass spectrum resolved finely enough to separate 1025.2 Da from 1024.2 Da. Every King Peptides lot carries its own certificate with HPLC and mass spectrometry; see the guide to checking a certificate of analysis. Orders leave the Netherlands as tracked parcels and usually need 1–2 business days to a Dutch address and 3–5 business days to Belgium and Luxembourg, with no customs clearance inside the EU. The guide to buying research peptides in the Benelux has the full supplier checklist.
PT-141: quick answers
Who is Vyleesi approved for? Premenopausal women in the United States with acquired, generalised HSDD, since 2019. Postmenopausal women and men are outside the approval.
Can bremelanotide darken the skin? Yes. The label reports focal hyperpigmentation in 1% of trial patients, and in 38% with daily dosing for eight days.
What did the phase 3 trials fail to show? A significant difference in the number of satisfying sexual events. The gains were on questionnaire scores for desire and distress.
Does King Peptides sell PT-141? No. Its closest product is Melanotan II 10 mg, a different compound that cannot stand in for bremelanotide.
Research use only. This page describes PT-141 for laboratory and scientific research. Research material has no marketing authorisation, whatever the status of the molecule as a medicine elsewhere, and is not meant for human or veterinary use. Nothing on this page is medical advice; the doses above are those reported in published studies, not recommendations. Check the rules that apply in your country and at your institution before ordering.