Pinc PeptideThe girly peptide research blog

Compare · updated 8 October 2026

Melanotan II vs PT-141

The short answer

PT-141 is bremelanotide, approved in the US as Vyleesi for low sexual desire in premenopausal women, while melanotan II is unapproved and was tested in people only in three tiny studies from 1996 to 2000123456. The two molecules are the same chain of seven amino acids closed into the same ring, and differ only at one end, and both act on MC1R, the skin-pigment receptor1789. Both caused nausea in trials, and frequent PT-141 use darkened patches of skin in 38% to 63% of people in short studies1351011. ‘PT-141’ vials sold online are not Vyleesi: FDA treats them as unapproved drugs, and Finnrick, a testing service, failed 53 of 151 samples from March 2025 to September 20261213.

At a glance

ComparedMelanotan IIPT-141 (bremelanotide)
Evidence tierB At least one controlled human trialA Two or more large human trials
Does it work?For tanning with less or no sun: UntestedBarely tested: in the only human tanning study we found, a 1996 pilot in which all 3 men got the drug, 2 got darker skin3. We found no larger tanning or long-term safety trial1415.For low sexual desire in women and men: Mixed resultsTwo large trials in women before menopause found slightly more desire than placebo, but not more frequent satisfying sex16. In men, the one large erection trial we found is under a journal’s expression of concern171819.
FDANot approved for any use6Approved as Vyleesi; vials are not212
US pharmaciesPharmacies may not make it202122Unclear whether pharmacies may make it223
SportNot named; likely caught by the catch-all ban2425Not named; approved in the US, so likely allowed24
AustraliaPrescription only26Not named in the Poisons Standard26
Half-lifeNot knownabout 2.7 hours (range 1.9–4.0 hours)1
Taken asSubcutaneous injection (the only route with human trial data we found)
Nasal spray (sold widely; no human trial data found)
Tablets (named by Australian news as a form it can be sold in; no human data found)
Intravenous, intraperitoneal and brain infusion (animal studies only)		Subcutaneous injection: the approved Vyleesi autoinjector; Phase 2 and Phase 3 human data
Intranasal spray: early Phase 1 and 2 studies in men and women; dropped because absorption varied
Intravenous: used in some early company studies
Gray-market vials are sold as powder for injection; nasal products were not verified
What it isA lab-made chain of seven amino acids closed into a ring, modeled on alpha-MSH, the body’s signal for skin pigment, sold online for tanning and not approved in the US36727.Bremelanotide, a modified version of melanotan II with the same ring but a free-acid end instead of an amide, approved as the Vyleesi autoinjector12928.
Main targetsSeveral melanocortin receptors at once: MC1R on pigment cells darkens skin, and MC3R and MC4R are linked to arousal and erections829.Acts most strongly on MC1R, on pigment cells, and on MC4R, found on nerve cells in many areas of the brain1.
Studied in people forErectile dysfunction, in two crossover trials of 10 men each, and tanning, in one pilot study of 3 men345.Low sexual desire in premenopausal women, in two Phase 3 trials of 1,267 women; work on erection problems in men was dropped after FDA raised concerns in 2007, and we found no results from a study in men announced in 20241619303132.
Best human resultIn 10 men whose erectile dysfunction had no known physical cause, 8 had erections on melanotan II, with 38.0 minutes of strong rigidity vs 3.0 on placebo4.From each woman’s start to her last visit (week 24 for those who finished), desire scores rose 0.30 and 0.42 points more than with placebo on a scale of 1.2 to 6, but the number of satisfying sexual events did not differ16.
Biggest documented riskCase reports of new or changing moles, melanoma, erections lasting many hours and kidney injury, though none proves cause20333435.Nausea in 40% of women in Phase 3, a blood pressure rise of up to 6 mmHg after each dose, and patchy skin darkening with frequent use11011.
Lab tests of gray-market vials67 of 182 Finnrick tests failed (February 2025 to September 2026), and a Danish hospital lab found 4.32 to 8.84 mg in vials labeled 10 mg3637.53 of 151 Finnrick tests failed (March 2025 to September 2026), and a vial from a Brooklyn corner shop, tested for WIRED, held no PT-1411338.

Vyleesi or a ‘PT-141’ vial: what is the difference?

Vyleesi is a prescription autoinjector holding 1.75 mg of bremelanotide, approved on 21 June 2019 for acquired, generalized hypoactive sexual desire disorder (HSDD): low desire that causes marked distress or interpersonal difficulty and has no other cause, in women before menopause12. Its label says it is not for men or postmenopausal women and not for enhancing sexual performance1.

‘PT-141’ is also sold online as a ‘research use only’ powder, for example in 10 mg vials39. On 24 August 2026, FDA warned five online sellers that the ‘PT-141’ they sold was an unapproved new drug1240414243. FDA has not reviewed the quality of these vials12. Finnrick, a testing service, failed 53 of 151 ‘PT-141’ samples from March 2025 to September 2026, and one vial bought at a Brooklyn corner shop, tested for a WIRED report published in September 2026, held none of the labeled peptide1338.

Melanotan II has no approved form at all: Drugs@FDA holds no application for it, and FDA has listed melanotan products since 9 April 2010 on an import alert that lets agents detain shipments without examining them644.

Do both darken the skin?

Both switch on MC1R, the receptor that tells pigment cells to make melanin18. Melanotan II is sold for this effect, but the only human tanning study found was a 1996 pilot in which 2 of 3 men had darker skin a week after their last dose327.

For PT-141, darkening is a side effect: patches on the face, gums or breasts appeared in 1% of women using up to 8 doses a month, but in 38% of people given 8 daily doses and 63% in a 15-day study with three doses a day11011. In Phase 3, fading was documented in only half of cases during follow-up111. An online dosing protocol still describes daily injections for 16 weeks, far beyond the label’s limit of 8 doses a month145.

With melanotan II, case reports describe new, darker or atypical moles appearing within days to weeks, and melanoma, often alongside sunbed use, though none proves cause33344647.

Questions people ask

Is PT-141 safer than melanotan II?

Only PT-141, as Vyleesi, has been through large trials and FDA approval, so its side effects are well described: nausea in 40% of women and a small rise in blood pressure after each dose116. Melanotan II has been tested only in tiny, short studies, and case reports link it to mole changes, melanoma, hours-long erections and kidney injury, though none proves cause345203335. Vyleesi’s safety data do not cover unapproved ‘PT-141’ vials, whose quality FDA has not reviewed12.

Does PT-141 tan your skin like melanotan II?

PT-141 is approved only for low sexual desire, not for tanning, but it acts strongly on MC1R, the skin-pigment receptor, and frequent use can darken patches of skin on the face, gums or breasts1. Darkening appeared in 1% of women at up to 8 doses a month but in 38% of people given 8 daily doses, and fading was documented in only half of the Phase 3 cases11011. Melanotan II is the one sold for tanning, and that use rests on one 1996 pilot in which 2 of 3 men got darker skin327.

Does melanotan II work for erectile dysfunction?

In two small crossover trials from 1998 and 2000, injections caused erections in men with erectile dysfunction, including 8 of 10 men whose problem had no known physical cause45. Each trial had only 10 men, and in one, severe nausea followed 4 of 19 injections45. It is not approved for this or any use, and case reports describe erections lasting many hours that needed emergency drainage or surgery6820.

Is a ‘PT-141’ research vial the same as Vyleesi?

No: the molecule is the same, but Vyleesi is an FDA-approved autoinjector, while ‘PT-141’ research vials have no approved application, so FDA has not reviewed their quality112. On 24 August 2026 FDA warned five online sellers that their ‘PT-141’ was an unapproved new drug1240414243. Finnrick, a testing service, failed 53 of 151 ‘PT-141’ samples from March 2025 to September 2026, and a vial bought at a Brooklyn corner shop held no PT-1411338.

Go deeper

Sources

  1. 1VYLEESI (bremelanotide injection) prescribing information Cosette Pharmaceuticals via DailyMed (U.S. National Library of Medicine), 13 Nov 2025. dailymed.nlm.nih.gov
  2. 2Drugs@FDA record for NDA 210557 (Vyleesi), openFDA drugsfda endpoint U.S. Food and Drug Administration (openFDA), 29 Sep 2026. api.fda.gov · data query
  3. 3Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study Life Sciences, 1996. pubmed.ncbi.nlm.nih.gov
  4. 4Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study The Journal of Urology, Aug 1998. pubmed.ncbi.nlm.nih.gov
  5. 5Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction Urology, 1 Oct 2000. pubmed.ncbi.nlm.nih.gov
  6. 6Drugs@FDA data (openFDA drugsfda endpoint): search for melanotan as an active ingredient, no matches U.S. Food and Drug Administration (openFDA), 29 Sep 2026. api.fda.gov · data query
  7. 7Melanotan II (CID 92432) PubChem, NCBI, accessed 1 Oct 2026. pubchem.ncbi.nlm.nih.gov
  8. 8Melanotan Tanning Injection: A Rare Cause of Priapism Sexual Medicine, Feb 2021. pubmed.ncbi.nlm.nih.gov
  9. 9Bremelanotide (CID 9941379) PubChem, NCBI, accessed 1 Oct 2026. pubchem.ncbi.nlm.nih.gov
  10. 10Effect of bremelanotide on body weight of obese women: Data from two phase 1 randomized controlled trials Diabetes, Obesity and Metabolism, Jun 2022. pmc.ncbi.nlm.nih.gov
  11. 11NDA 210557 Multi-discipline Review and Evaluation (bremelanotide) U.S. Food and Drug Administration, CDER, Jun 2019. accessdata.fda.gov
  12. 12Warning letter to Peak Performance Peptides (MARCS-CMS 735127) U.S. Food and Drug Administration, 24 Aug 2026. fda.gov
  13. 13PT-141 Safety Testing Results & Vendor Ratings Finnrick, accessed 8 Oct 2026. finnrick.com
  14. 14PubMed search: melanotan in titles or abstracts, limited to clinical trials (8 results; 4 report the three melanotan II studies, 4 test melanotan I) National Library of Medicine (PubMed), accessed 8 Oct 2026. pubmed.ncbi.nlm.nih.gov
  15. 15ClinicalTrials.gov search for ‘melanotan’ (1 study: the ‘example’ record NCT07437560) ClinicalTrials.gov, accessed 8 Oct 2026. clinicaltrials.gov
  16. 16Bremelanotide for the Treatment of Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials Obstetrics & Gynecology, Nov 2019. pubmed.ncbi.nlm.nih.gov
  17. 17Salvage of sildenafil failures with bremelanotide: a randomized, double-blind, placebo controlled study The Journal of Urology, Mar 2008. pubmed.ncbi.nlm.nih.gov
  18. 18Expression of Concern: Salvage of Sildenafil Failures With Bremelanotide: A Randomized, Double-Blind, Placebo Controlled Study The Journal of Urology, 10 Jan 2023. pubmed.ncbi.nlm.nih.gov
  19. 19PubMed search: (bremelanotide OR “PT-141” OR “PT 141”) AND (erectile OR men OR male), limited to clinical trials and randomized controlled trials (6 results on 8 October 2026; the only large trial is a 2008 trial of 342 men under an expression of concern) National Library of Medicine (PubMed), accessed 8 Oct 2026. pubmed.ncbi.nlm.nih.gov
  20. 20Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks U.S. Food and Drug Administration, 22 Apr 2026. fda.gov
  21. 21Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the Federal Food, Drug, and Cosmetic Act (categories list) U.S. Food and Drug Administration, 14 May 2026. fda.gov
  22. 22FDA to Remove 12 Popular Peptides from the Category 2 ‘Do Not Compound’ List Frier Levitt, 16 Apr 2026. frierlevitt.com
  23. 23Bulk Drug Substances Used in Compounding Under Section 503A of the FD&C Act U.S. Food and Drug Administration, 14 May 2026. fda.gov
  24. 24World Anti-Doping Code International Standard: Prohibited List 2026 World Anti-Doping Agency, 24 Sep 2025. wada-ama.org
  25. 25World Anti-Doping Code International Standard: Prohibited List 2027 World Anti-Doping Agency, 21 Sep 2026. wada-ama.org
  26. 26Therapeutic Goods (Poisons Standard—October 2026) Instrument 2026 (F2026L01327) Federal Register of Legislation, Australian Government, 28 Sep 2026. legislation.gov.au
  27. 27Inside the Weird New World of Peptide Tanning GQ, 12 Aug 2026. gq.com
  28. 28Melanocortin peptide therapeutics: historical milestones, clinical studies and commercialization Peptides, Apr 2006. pubmed.ncbi.nlm.nih.gov
  29. 29Melanocortin receptor agonists, penile erection, and sexual motivation: human studies with Melanotan II International Journal of Impotence Research, Oct 2000. pubmed.ncbi.nlm.nih.gov
  30. 30King Pharmaceuticals and Palatin Technologies delay immediate plans for Phase 3 clinical program with bremelanotide for erectile dysfunction (Form 8-K, Exhibit 99) Palatin Technologies via SEC EDGAR, 30 Aug 2007. sec.gov
  31. 31Palatin Technologies Form 10-K for the fiscal year ended June 30, 2008 Palatin Technologies via SEC EDGAR, 29 Sep 2008. sec.gov
  32. 32Palatin Announces the Initiation of a Phase 2 Clinical Study of Bremelanotide Co-Administered with a PDE5i for the Treatment of Erectile Dysfunction (ED) Palatin Technologies, 20 Jun 2024. palatin.com
  33. 33Risks of unregulated use of alpha-melanocyte-stimulating hormone analogues: a review International Journal of Dermatology, Oct 2017. pubmed.ncbi.nlm.nih.gov
  34. 34Five primary melanomas in situ in a patient with recent tanning bed use, melanotan exposure, and anabolic hormone use JAAD Case Reports, Jul 2026. pubmed.ncbi.nlm.nih.gov
  35. 35Melanotan II injection resulting in systemic toxicity and rhabdomyolysis Clinical Toxicology, Dec 2012. pubmed.ncbi.nlm.nih.gov
  36. 36Identification and characterization by LC-UV-MS/MS of melanotan II skin-tanning products sold illegally on the Internet Drug Testing and Analysis, Feb 2015. pubmed.ncbi.nlm.nih.gov
  37. 37Melanotan II Safety Testing Results & Vendor Ratings Finnrick, accessed 1 Oct 2026. finnrick.com
  38. 38Those Viral Bodega Peptides Aren’t Actually Peptides WIRED, 15 Sep 2026. wired.com
  39. 39PT-141 (Bremelanotide) – 10MG product page Core Peptides (vendor), accessed 8 Oct 2026. corepeptides.com (seller page, deliberately not linked)
  40. 40Warning letter to Royal Peptides LLC (MARCS-CMS 734884) U.S. Food and Drug Administration, 24 Aug 2026. fda.gov
  41. 41Warning letter to NuScience Peptides LLC (MARCS-CMS 733652) U.S. Food and Drug Administration, 24 Aug 2026. fda.gov
  42. 42Warning letter to Peptide Partners LLC (MARCS-CMS 735063) U.S. Food and Drug Administration, 24 Aug 2026. fda.gov
  43. 43Warning letter to TXP Innovations LLC dba Tex Peptides (MARCS-CMS 735067) U.S. Food and Drug Administration, 24 Aug 2026. fda.gov
  44. 44Import Alert 66-41: Detention Without Physical Examination of Unapproved New Drugs Promoted In The U.S. U.S. Food and Drug Administration, 1 Oct 2026. accessdata.fda.gov
  45. 45PT-141 (10 mg Vial) Dosage Protocol PeptideDosages.com, 20 Sep 2026. peptidedosages.com
  46. 46Atypical melanocytic naevi following melanotan injection Irish Medical Journal, May 2013. pubmed.ncbi.nlm.nih.gov
  47. 47Melanoma associated with the use of melanotan-II Dermatology, 2014. pubmed.ncbi.nlm.nih.gov

Not medical advice. Neither compound is recommended here. How we grade evidence · Report an error.