Peptide / SubQ, Intranasal / 1.75mg as needed (max 1x/day)
PT-141 (Bremelanotide)
PT-141 came out of a suntan program: a cyclic copy of the pigment hormone alpha-MSH, built at the University of Arizona in the late 1980s to darken skin without sunlight, whose first human study recorded unplanned erections alongside the tanning it was testing for. The sexual-medicine program that followed ended in an FDA approval in 2019, while the parent peptide went to the tanning grey market and stayed there.
In plain words
PT-141, approved under the name bremelanotide, is a lab-made ring-shaped peptide from the same family as the tanning peptide melanotan-II; the two are the same seven residues with a different cap on one end. Unlike melanotan-II, it finished a full trial program: the FDA approved it in 2019 as a self-injection for premenopausal women with a diagnosis of low sexual desire that causes them distress. Two large randomized trials did beat placebo, but the improvements were small, about a third of a point on each of the two rating scales, and a later re-analysis of the same data found that people were far more likely to quit the drug than placebo because of side effects and, on a combined measure of finishing the trial and choosing to continue, leaned toward placebo. The side effects are common rather than rare: nausea in about 40 percent of treated women against about 1 percent on placebo, plus flushing, headache and a temporary rise in blood pressure after every dose, which is why the label rules it out for people with uncontrolled high blood pressure or known heart disease. It also darkens patches of skin, including the face and gums, and the more often it is given the more often that happens. Most grey-market use is by men buying research-labeled powder for erection effects, which is not what the approved trials tested; the erection effect was first shown with the parent peptide melanotan-II in ten men, and PT-141's own erection studies were small dose-ranging trials that were set aside before any approval for that use.
At a glance
| Half-life | 0.11 days |
|---|---|
| Tmax | 0.042 days |
| Route(s) | SubQ, Intranasal |
| Published dosing range | 1.75mg as needed (max 1x/day) |
| Vial strengths | 10, 5 mg |
Reference data from the DosePlot canon -- not a protocol recommendation.
Serum curve
Single 1.75 mg dose by SubQ, rendered from the same engine that powers the interactive chart. Relative levels, not lab values.
What does the evidence show?
Two things are labeled separately here because they answer different questions. The tier is how a study was built. The distance chips are whether that study touched this molecule, by this route, in a population resembling the reader. A randomized trial of a different molecule keeps its tier and still says nothing about this compound.
| Finding | Tier | Distance from use | Study |
|---|---|---|---|
| Two identical 24-week randomized, double-blind, placebo-controlled trials (RECONNECT) tested 1.75 mg subcutaneously as needed in premenopausal women with hypoactive sexual desire disorder. Of 1,267 women randomized, 1,202 were evaluable for efficacy. The drug beat placebo on both co-primary endpoints: desire improved by 0.35 points on the Female Sexual Function Index desire domain (study 301, 0.30; study 302, 0.42; P less than .001 integrated) and distress fell by 0.33 points on item 13 of the Female Sexual Distress Scale (study 301, -0.37; study 302, -0.29; P less than .001 integrated). Nausea, flushing and headache each occurred in 10 percent or more of treated women in both studies. | rct | not recorded | Kingsberg SA, Clayton AH, Portman D, et al. Bremelanotide for the treatment of hypoactive sexual desire disorder: two randomized phase 3 trials.Obstetrics and Gynecology 134(5):899-908, 2019 |
| The dose-finding trial that set the 1.75 mg dose randomized 397 premenopausal women to placebo or 0.75, 1.25 or 1.75 mg self-administered subcutaneously for 12 weeks. Of those, 394 received at least one in-clinic dose and 327 supplied data after the first four weeks of double-blind treatment; 327 is the efficacy population, not the number randomized. Pooling the 1.25 and 1.75 mg arms, satisfying sexual events rose by 0.7 per month against 0.2 on placebo (p equals 0.0180), total Female Sexual Function Index score rose 3.6 against 1.9 (p equals 0.0017), and the distress score fell 11.1 against 6.8 (p equals 0.0014). | rct | not recorded | Clayton 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 12(3):325-337, 2016 |
| A published re-analysis of the phase 3 data, drawn from the FDA New Drug Application, reproduced the reported efficacy results but added two findings the trial report omitted. Discontinuation caused by an adverse event was far higher on drug (odds ratio 11.98, 95 percent confidence interval 3.74 to 38.37, number needed to harm 6). And on a combined measure of completing the trial and then choosing to enter the open-label follow-up, participants favored placebo (odds ratio 0.30, 95 percent confidence interval 0.24 to 0.38, number needed to harm 4). The same analysis found that 72.72 percent of the outcomes listed in the study protocols were not reported. | clinical | not recorded | Spielmans GI. Re-analyzing phase III bremelanotide trials for 'hypoactive sexual desire disorder' in women.Journal of Sex Research 58(9):1085-1105, 2021 |
| Nausea is the defining side effect and it is common. In the pooled phase 3 safety population (627 treated, 620 placebo) nausea occurred in 40.0 percent against 1.3 percent on placebo, flushing in 20.3 percent against 0.3 percent, injection site reactions in 13.2 percent against 8.4 percent, headache in 11.3 percent against 1.9 percent and vomiting in 4.8 percent against 0.2 percent. About 13 percent of treated patients needed an anti-emetic and about 8 percent stopped because of nausea. Every dose also raises blood pressure transiently, by a mean maximum of about 6 mmHg systolic and 3 mmHg diastolic 2 to 4 hours after injection, with heart rate falling up to 5 beats per minute and both returning toward baseline within about 12 hours. The drug is contraindicated in uncontrolled hypertension or known cardiovascular disease, and the ceiling of one dose per 24 hours exists partly because closer dosing risks additive blood pressure effects. | clinical | not recorded | Cosette Pharmaceuticals. VYLEESI (bremelanotide injection) prescribing information, sections 4, 5.1, 5.3 and 6.1.US FDA prescribing information, NDA 210557, revised March 2024 |
| The drug darkens skin, and how much depends on how often it is given. In the phase 3 trials, focal hyperpigmentation, including the face, gums and breasts, was reported in 1 percent of patients taking up to 8 doses per month and in none of the placebo patients. In a separate study, 38 percent of patients developed focal hyperpigmentation after taking it daily for 8 days, and among those who continued daily for 8 more days a further 14 percent developed new pigmentary changes. Patients with dark skin were more likely to be affected, and resolution after stopping was not confirmed in all patients. | clinical | not recorded | Cosette Pharmaceuticals. VYLEESI (bremelanotide injection) prescribing information, section 5.2, Focal Hyperpigmentation.US FDA prescribing information, NDA 210557, revised March 2024 |
| The human erection effect was first shown with the parent peptide, melanotan-II, not with PT-141. In a double-blind, placebo-controlled crossover study of 10 men with psychogenic erectile dysfunction, 0.025 mg per kg subcutaneously produced a clinically apparent erection in 8 of 10, and rigidity above 80 percent at the penile tip lasted a mean of 38.0 minutes against 3.0 minutes on placebo (p equals 0.0045). Nausea, stretching and yawning, and reduced appetite were reported but needed no treatment. Ten men is a small sample, and the finding was never carried through a registrational program. | clinical | not recorded | Wessells H, Fuciarelli K, Hansen J, et al. Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study.Journal of Urology 160(2):389-393, 1998 |
| Animal work is what pointed the molecule at desire rather than at erection. In female rats, PT-141 increased solicitational behavior, the approach and courtship signals that precede mating, without changing lordosis or other components of receptivity. That separation, wanting affected and mechanics untouched, is the pharmacological basis for a desire indication and remains an animal finding; the label states plainly that the mechanism by which the drug improves the disorder in women is unknown. | preclinical | not recorded | Pfaus 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 101(27):10201-10204, 2004 |
| Outside the approved indication the peptide is bought as lyophilized powder labeled for research, reconstituted with bacteriostatic water and injected subcutaneously, most often by men using it for erectile or libido effects rather than by women with the diagnosed condition. Reported doses cluster below and above the approved 1.75 mg, sometimes split across part-vials with no way to confirm what is in them. Nausea and facial flushing are near-universal in these reports and are the usual reason people stop. Community accounts of intranasal use persist even though that formulation was never approved. | anecdotal | not recorded | community reports aggregated from reddit, MESO-Rx, and similar forumsno study |
How did it get here?
- preclinical1989
- Victor Hruby, Mac Hadley and colleagues at the University of Arizona are building superpotent analogs of alpha-MSH, the hormone that tells melanocytes to make pigment. Melanotan-II, a seven-residue peptide cyclized through a lactam bridge, is synthesized this year. The stated goal is a drug that produces a tan without ultraviolet exposure.
- first-human1996
- A pilot phase 1 study gives melanotan-II to three healthy male volunteers by subcutaneous injection on alternating days, starting at 0.01 mg per kg. Two are escalated in 0.005 mg per kg steps to 0.03 mg per kg and the third to 0.025. Two of the three show increased pigmentation of the face, upper body and buttock a week after five doses, which is what the study was looking for. The paper also records spontaneous erections, intermittently experienced for one to five hours after dosing and correlating with a stretching-and-yawning complex, plus mild nausea at most dose levels. The recommended dose for future work is set at 0.025 mg per kg per day.
- first-human1998
- The erection finding is tested deliberately. Ten men with psychogenic erectile dysfunction receive 0.025 mg per kg in a double-blind placebo-controlled crossover; eight respond, with tip rigidity above 80 percent lasting a mean of 38 minutes against 3 minutes on placebo. A tanning peptide has become a sexual-medicine candidate on the strength of its side-effect column.
- clinical-adoption2003-2007
- Palatin Technologies develops PT-141, the free-acid form of the same molecule, for erectile dysfunction. Two 2004 dose-ranging reports fix the working doses. Diamond and colleagues find that intranasal PT-141 separates from placebo on erectile response only at doses greater than 7 mg; Rosen and colleagues find that subcutaneous injection does so at doses greater than 1.0 mg. Blood pressure increase becomes the effect that limits dose and frequency, the intranasal program does not reach approval, and the erectile dysfunction indication is set aside for female hypoactive sexual desire disorder at a much lower subcutaneous dose.
- clinical-adoption2011-2019
- The dose-finding trial runs from June 2011 to September 2012, randomizes 397 women and settles on 1.75 mg. Two 24-week phase 3 trials randomize 1,267 women between January 2015 and August 2016, and the FDA approves the drug as Vyleesi on 21 June 2019, with a limit of one dose per 24 hours and no more than eight doses per month recommended. Four months later, on 8 October 2019, the FDA approves a different melanocortin, afamelanotide, as a 16 mg implant for erythropoietic protoporphyria. Two melanocortin drugs are approved in one year, and neither of them is melanotan-II.
- grey-market2007-present
- No sponsor ever takes melanotan-II through a registrational program. It sells instead as lyophilized powder for home reconstitution, injected to build a tan, and the dermatology literature accumulates reports of eruptive melanocytic nevi, darkening of existing moles and a melanoma diagnosed during use. PT-141 travels the same channel in the same kind of vial, bought mostly by men for a use its trials never studied. It also reaches off-label use by a second and more regulated route: several suppliers list bremelanotide in the FDA National Drug Code directory as a bulk ingredient for human prescription compounding, so compounded prescriptions sit alongside the research-labeled powder.
How is it made?
Production happens in four stages.
1. Building the chain. Bremelanotide is a seven-residue peptide, built one residue at a time on a resin bead. The chain grows tail first: lysine anchors to the resin, then tryptophan, arginine, D-phenylalanine, histidine, aspartic acid and norleucine, and the free end is acetylated. Four residues depart from the alpha-MSH fragment it copies: norleucine for an easily oxidized methionine, D-phenylalanine for its ordinary mirror image, aspartic acid for glutamic acid, lysine for glycine. The first two slow enzymatic breakdown; the last two anchor the ring.
2. Closing the ring. The aspartic acid side chain is bonded to the lysine side chain, forming a lactam bridge that closes the loop. It is run dilute so molecules close on themselves, not on each other. The ring is why this family is far more potent and longer lived than alpha-MSH itself.
3. Choosing the end. A resin that leaves a free acid gives bremelanotide; one that leaves an amide gives melanotan-II. Everything upstream is identical.
4. Purifying and filling. Strong acid frees the peptide and strips its protecting groups; the crude is purified by reverse-phase chromatography and freeze-dried as an acetate salt. The approved product is a sterile solution, 1.75 mg in 0.3 mL, in a single-use autoinjector tested batch by batch for identity, potency, sterility and endotoxin. What varies outside regulated manufacturing is the finishing, not the sequence: how much crude is carried through, what solvent residue is left, and whether anything is tested.
Worth knowing
The sexual-medicine program exists because of a line in an adverse-events table. The 1996 pilot study was a tanning study: three healthy men, dosing started at 0.01 mg per kg and escalated to 0.03 in two of them and 0.025 in the third, endpoint skin pigmentation, which increased in two of the three after five doses. The paper also records spontaneous erections, intermittently experienced for one to five hours after dosing, alongside mild nausea and a stretching-and-yawning complex, and recommends 0.025 mg per kg per day for future studies. Everything downstream, including an approved drug, follows from that observation.
Dorr RT, Lines R, Levine N, et al. Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study.Life Sciences 58(20):1777-1784, 1996
PT-141 and melanotan-II are the same peptide with different endings. A 2007 review describes PT-141 flatly as the carboxylate derivative of melanotan-II: same seven residues, same lactam ring, with the C-terminal amide replaced by a free carboxylic acid. The formulas are C50H69N15O9 (mass 1024.2) and C50H68N14O10 (mass 1025.2), a difference of one nitrogen for one oxygen. In manufacturing that difference is a choice of resin made before the first amino acid is attached. One choice produces an FDA-approved drug; the other produces a peptide no regulator has ever approved for anything.
King SH, Mayorov AV, Balse-Srinivasan P, Hruby VJ, Vanderah TW, Wessells H. Melanocortin receptors, melanotropic peptides and penile erection.Current Topics in Medicinal Chemistry 7(11):1098-1106, 2007
The pigment effect that made melanotan-II popular is the same receptor action the approved drug's label warns about, and it has a documented downside. A 2014 case report describes a melanoma diagnosed in a melanotan-II user, and separate dermatology reports describe eruptive melanocytic nevi and darkening of existing moles appearing during use. Case reports cannot establish that the peptide causes melanoma. What they do establish is that a drug whose entire purpose is to drive melanocyte activity makes existing pigmented lesions change appearance, which is exactly the signal skin cancer screening depends on.
Hjuler KF, Lorentzen HF. Melanoma associated with the use of melanotan-II.Dermatology 228(1):34-36, 2014
Reconstitution
PT-141 (Bremelanotide) ships lyophilized and is mixed before use; the published vial strengths are 10, 5 mg. The water volume you add sets the concentration, not the dose -- the calculator turns a vial size and a water volume into mg/mL, draw volume, and units on an insulin syringe.
Open in the reconstitution calculatorWritten and reviewed by Evan Marlow, developer of DosePlot · Updated 2026-08-27
Not medical advice. DosePlot is an informational tool, not a healthcare provider, and using it creates no provider-patient relationship. Do not start, stop, or change any protocol without the approval of a licensed healthcare professional.
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