what is the difference
PT-141 and melanotan II
A metabolite and the molecule it comes from, set out on what each one is and what has actually been published about it.
PT-141 is bremelanotide, a seven amino acid ring-shaped peptide that acts on melanocortin receptors in the brain rather than on blood flow. The FDA approved it as Vyleesi in June 2019 for acquired, generalised hypoactive sexual desire disorder in premenopausal women, and the labelling for that product is published in the FDA labelling database DailyMed [11]. Melanotan II is a seven amino acid ring-shaped analog of alpha-melanocyte-stimulating hormone, the hormone that drives pigmentation, and it is sold for a cosmetic tan. Searching DailyMed on 2 August 2026 returns no label under the name melanotan at all [11].
The two are related by metabolism. Bremelanotide is one of the breakdown products of melanotan II, which is a fact about chemistry and is the reason accounts of melanotan II describe sexual effects alongside pigmentation. What the relationship does not do is move evidence between them. Two randomised phase 3 trials tested bremelanotide in a defined population and a defined condition, and those trials say nothing about the parent molecule.
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The short answer
One of these has an approval and a completed randomised programme behind it, and the other has a single recruiting registration and a case-report literature. PT-141 is the approved one, and the same molecule appears under three names.
A product sold as PT-141 is not the approved product, and the approval reaches one condition in one population. Melanotan II holds no approval anywhere, and almost everything documented about it in the last twenty years is a report of what happened to one person.
Side by side
| Property | PT-141 | Melanotan II |
|---|---|---|
| What it is | Bremelanotide, a seven amino acid cyclic melanocortin receptor agonist, also sold under the brand name Vyleesi | A seven amino acid cyclic analog of alpha-melanocyte-stimulating hormone, less selective across the melanocortin receptors |
| Relationship to the other | One of the breakdown products of melanotan II | The parent molecule that bremelanotide comes from |
| Regulatory position | FDA approved as Vyleesi in June 2019 for acquired, generalised hypoactive sexual desire disorder in premenopausal women. Labelling published in DailyMed | No approval anywhere. DailyMed returns no label under the name melanotan, searched 2 August 2026 |
| Completed randomised trials for the marketed use | Two, published together in Obstetrics and Gynecology in 2019, with 723 and 714 participants | None. The one registered study is recruiting and concerns repigmentation in vitiligo rather than tanning |
| Registrations on ClinicalTrials.gov | 10 under bremelanotide and 4 under PT-141, which are one molecule indexed twice and are not additive | 1, NCT07437560, a phase 2 study alongside narrowband UVB phototherapy for stable non-segmental vitiligo, recruiting with nothing posted |
| Earliest published human work | A 2004 double-blind, placebo-controlled study in the International Journal of Impotence Research, of an intranasal formulation, in healthy men and in men with mild to moderate erectile dysfunction | A 2000 paper in the same journal, in which the authors reviewed their own double-blind, placebo-controlled crossover experience in 20 men with erectile dysfunction |
| Published criticism of the result | Two papers in the Journal of Sex Research, a 2021 re-analysis of the phase 3 data and a 2024 examination of the outcome measures those trials used | None found. There is no efficacy result of that scale to argue about |
| Pigmentation on the record | Focal hyperpigmentation is recorded in the approved labelling as an adverse reaction, with a higher share reported under repeated exposure | Three published case reports describe pigmented lesions in people who had injected it for a cosmetic tan, and a fourth describes new and darkening moles the day after a single injection |
| Other published harm reports | Adverse reactions are recorded in the approved labelling, from the trials that supported the approval | Case reports describe priapism, posterior reversible encephalopathy syndrome, renal infarction and systemic toxicity with rhabdomyolysis, each a single case or a small series |
| What has never been tested | The approval covers premenopausal women with one diagnosis. No trial supports a statement about anyone outside that population | Cosmetic tanning, the use it is actually sold for, which no published study of any design has measured |
| WADA 2026 Prohibited List | Not named on the list, and its current FDA approval as Vyleesi places it outside the S0 catch-all, whose definition covers only substances with no current approval by any governmental regulatory health authority [12] | Reached by the S0 catch-all, covering any pharmacological substance not addressed by another section of the list and with no current approval by any governmental regulatory health authority, prohibited at all times [12] |
Why the two get mixed up
The metabolite relationship is the root of it, and unlike most of the confusions on this site it is chemically real. Melanotan II breaks down in the body into several fragments, and bremelanotide is one of them. Somebody meeting that fact reasonably concludes that the parent contains the metabolite's activity, and then treats a trial of one as evidence about the other. Under this site's rules that inference gets no tier: two molecules, two evidence bases, and a metabolite is a different substance from what it came out of.
Naming does the rest of the work. Bremelanotide, PT-141 and Vyleesi are one molecule with three names, and a search on any of them returns the phase 3 result. Melanotan II is sold as MT-2 and MT-II, and both compounds sit in the same product copy under the same phrase, melanocortin agonist. A reader who has just learned that the two are chemically connected, and who then sees an approval attached to one of the names, has reason to think the approval is about the family.
The early human literature reinforces it by accident. The 2000 melanotan II report and the 2004 PT-141 report appeared in the same journal four years apart, and both concern erectile response in men [5] [6]. Read side by side they look like one research line. What followed diverged completely, and only one of the two molecules ever reached a registered phase 3 programme.
What the published record covers for each
The approval rests on the RECONNECT programme. Two randomised phase 3 trials, with 723 and 714 participants, were published together in Obstetrics and Gynecology in 2019 and reported a difference against placebo on the desire and distress measures they used [Human RCT] [1]. A long-term open-label extension was published alongside them [2].
That result has a published critical literature, and it belongs on the page with the trials rather than under them. A 2021 re-analysis of the phase 3 data and a 2024 paper examining the outcome measures those trials used, both in the Journal of Sex Research, argued that the measured difference was small and that the instruments used to detect it were open to question [Human RCT] [3] [4]. The two sides of that argument disagree about the size of the same result rather than about whether it occurred, and the tier stays where the design puts it.
The pigmentation signal runs across this chemical family and it is documented at both ends of the pair. The approved labelling for the metabolite records focal hyperpigmentation, including on the face, gums and breasts, in 1 percent of patients who received the drug and in none who received placebo, and in 38 percent of patients in a separate study of repeated exposure on consecutive days. The same labelling records that resolution after stopping was not confirmed in every patient [Human RCT] [11].
The parent molecule has one old human study and a case-report literature. A 2000 paper in the International Journal of Impotence Research reported the authors' own double-blind, placebo-controlled crossover experience giving melanotan II to 20 men with erectile dysfunction: penile erection in 17 of 20, higher reported desire against placebo, and nausea and yawning as frequent side effects, with severe nausea in a share of subjects. PubMed indexes it as a controlled clinical trial rather than a randomised one, so it carries the open-label tier here [Human open-label] [6].
Three published case reports describe pigmented lesions in people who had injected melanotan II for a cosmetic tan: a melanoma in the British Journal of Dermatology [7], a melanoma associated with melanotan-II in Dermatology [8], and a melanoma in situ in the Australasian Journal of Dermatology [9] [Anecdote]. A separate report in BMJ Case Reports describes priapism, a prolonged and painful erection, in a man who had injected it [Anecdote] [10]. Each of those is one person. A case report carries no denominator, so it cannot establish how often anything happens, in either direction.
Our takeThe chemistry connects these two and the records do not. One went through a phase 3 programme that reported, got approved, and then got argued about in print. The other stopped in 2000 and the literature since has been case reports.
Frequently asked questions
Is PT-141 the same thing as melanotan II?
No. PT-141 is bremelanotide, and bremelanotide is one of the breakdown products of melanotan II. They are two different molecules with a metabolic relationship, and the relationship does not transfer evidence in either direction. The phase 3 trials tested bremelanotide [1], and nothing in them is a finding about melanotan II.
Is PT-141 the same as bremelanotide and Vyleesi?
Yes, all three names describe one molecule, which is why the registry counts do not add up. On 2 August 2026 ClinicalTrials.gov returned 10 registrations under bremelanotide and 4 under PT-141, and those are the same programme indexed twice. A product sold under the research name is not the approved product, whatever the shared molecule.
What did the phase 3 trials measure, and what did the critics say?
The two RECONNECT trials randomised 723 and 714 participants and measured desire and distress on questionnaire instruments [1], with a long-term open-label extension published alongside them [2]. Two later papers in the Journal of Sex Research argued the difference against placebo was small and questioned the outcome measures used to detect it [3] [4]. Both sets of papers are part of the record.
Has melanotan II ever been given to people in a study?
Once, on the published record, and a long time ago. A 2000 paper in the International Journal of Impotence Research reported a double-blind, placebo-controlled crossover in 20 men with erectile dysfunction, with penile erection reported in 17 of 20 and nausea and yawning as frequent side effects [6]. Since then the published literature on it has been case reports. Its one registration, NCT07437560, is a recruiting vitiligo study rather than anything about tanning.
Does either one change skin pigmentation?
Pigmentation appears in both records, by different routes. The approved labelling for bremelanotide records focal hyperpigmentation as an adverse reaction, in 1 percent of patients in the trials and in a much higher share under repeated exposure, and notes that resolution after stopping was not confirmed in every patient [11]. For melanotan II, three published case reports describe pigmented lesions in people who had injected it [7] [8] [9], and a fourth describes new and darkening moles the day after a single injection. None of those supplies a rate.
Are both prohibited in sport?
Not both, and the asymmetry is the answer. Melanotan II is reached by the S0 class of the 2026 WADA Prohibited List, which catches any pharmacological substance not addressed by another section of the list and with no current approval by any governmental regulatory health authority, and S0 substances are prohibited at all times rather than in competition only [12]. PT-141 is different: bremelanotide holds a current FDA approval as Vyleesi, which places the substance outside S0's own definition, and it is not named anywhere on the 2026 list [12]. S0 turns on the substance's approval status, not on which vial it came from, so a research-labelled bremelanotide product does not re-enter S0 by its label. Anti-doping status is decided by an athlete's own anti-doping organization against the current list, and that is the only body whose answer counts.
References
- Kingsberg SA, Clayton AH, Portman D, Williams LA, Krop J, Jordan R, Lucas J, Simon JA. Bremelanotide for the Treatment of Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials. Obstet Gynecol. 2019. PMID 31599840 DOI 10.1097/AOG.0000000000003500
- Simon JA, Kingsberg SA, Portman D, Williams LA, Krop J, Jordan R, Lucas J, Clayton AH. Long-Term Safety and Efficacy of Bremelanotide for Hypoactive Sexual Desire Disorder. Obstet Gynecol. 2019. PMID 31599847 DOI 10.1097/AOG.0000000000003514
- Spielmans GI. Re-Analyzing Phase III Bremelanotide Trials for "Hypoactive Sexual Desire Disorder" in Women. J Sex Res. 2021. PMID 33678061 DOI 10.1080/00224499.2021.1885601
- Spielmans GI, Ellefson EM. Small Effects, Questionable Outcomes: Bremelanotide for Hypoactive Sexual Desire Disorder. J Sex Res. 2024. PMID 36809187 DOI 10.1080/00224499.2023.2175192
- Diamond 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. Int J Impot Res. 2004. PMID 14963471 DOI 10.1038/sj.ijir.3901139
- Wessells H, Levine N, Hadley ME, Dorr R, Hruby V. Melanocortin receptor agonists, penile erection, and sexual motivation: human studies with Melanotan II. Int J Impot Res. 2000. PMID 11035391 DOI 10.1038/sj.ijir.3900582
- Paurobally D, Jason F, Dezfoulian B, Nikkels AF. Melanotan-associated melanoma. Br J Dermatol. 2011. PMID 21564053 DOI 10.1111/j.1365-2133.2011.10273.x
- Hjuler KF, Lorentzen HF. Melanoma associated with the use of melanotan-II. Dermatology. 2014. PMID 24355990 DOI 10.1159/000356389
- Ong S, Bowling J. Melanotan-associated melanoma in situ. Australas J Dermatol. 2012. PMID 22724573 DOI 10.1111/j.1440-0960.2012.00915.x
- Dreyer BA, Amer T, Fraser M. Melanotan-induced priapism: a hard-earned tan. BMJ Case Rep. 2019. PMID 30796078 DOI 10.1136/bcr-2018-227644
- US National Library of Medicine, DailyMed. VYLEESI (bremelanotide injection) prescribing information, as published in the FDA labelling database. Searched 2 August 2026, when the same database returned no label under the name melanotan. DailyMed, National Library of Medicine. 2026. DailyMed label
- World Anti-Doping Agency. The 2026 Prohibited List, international standard, effective 1 January 2026. WADA. 2026. Source document